The Tor Browser: comparison media/libpng/pngrtran.c

--1:000000000000
+:f7bdb9d06ede
+/* pngrtran.c - transforms the data in a row for PNG readers
+*
+* Last changed in libpng 1.6.10 [March 6, 2014]
+* Copyright (c) 1998-2014 Glenn Randers-Pehrson
+* (Version 0.96 Copyright (c) 1996, 1997 Andreas Dilger)
+* (Version 0.88 Copyright (c) 1995, 1996 Guy Eric Schalnat, Group 42, Inc.)
+*
+* This code is released under the libpng license.
+* For conditions of distribution and use, see the disclaimer
+* and license in png.h
+*
+* This file contains functions optionally called by an application
+* in order to tell libpng how to handle data when reading a PNG.
+* Transformations that are used in both reading and writing are
+* in pngtrans.c.
+*/
+#include "pngpriv.h"
+#ifdef PNG_READ_SUPPORTED
+/* Set the action on getting a CRC error for an ancillary or critical chunk. */
+void PNGAPI
+png_set_crc_action(png_structrp png_ptr, int crit_action, int ancil_action)
+{
+png_debug(1, "in png_set_crc_action");
+if (png_ptr == NULL)
+return;
+/* Tell libpng how we react to CRC errors in critical chunks */
+switch (crit_action)
+{
+case PNG_CRC_NO_CHANGE:                        /* Leave setting as is */
+break;
+case PNG_CRC_WARN_USE:                               /* Warn/use data */
+png_ptr->flags &= ~PNG_FLAG_CRC_CRITICAL_MASK;
+png_ptr->flags |= PNG_FLAG_CRC_CRITICAL_USE;
+break;
+case PNG_CRC_QUIET_USE:                             /* Quiet/use data */
+png_ptr->flags &= ~PNG_FLAG_CRC_CRITICAL_MASK;
+png_ptr->flags |= PNG_FLAG_CRC_CRITICAL_USE |
+PNG_FLAG_CRC_CRITICAL_IGNORE;
+break;
+case PNG_CRC_WARN_DISCARD:    /* Not a valid action for critical data */
+png_warning(png_ptr,
+"Can't discard critical data on CRC error");
+case PNG_CRC_ERROR_QUIT:                                /* Error/quit */
+case PNG_CRC_DEFAULT:
+default:
+png_ptr->flags &= ~PNG_FLAG_CRC_CRITICAL_MASK;
+break;
+}
+/* Tell libpng how we react to CRC errors in ancillary chunks */
+switch (ancil_action)
+{
+case PNG_CRC_NO_CHANGE:                       /* Leave setting as is */
+break;
+case PNG_CRC_WARN_USE:                              /* Warn/use data */
+png_ptr->flags &= ~PNG_FLAG_CRC_ANCILLARY_MASK;
+png_ptr->flags |= PNG_FLAG_CRC_ANCILLARY_USE;
+break;
+case PNG_CRC_QUIET_USE:                            /* Quiet/use data */
+png_ptr->flags &= ~PNG_FLAG_CRC_ANCILLARY_MASK;
+png_ptr->flags |= PNG_FLAG_CRC_ANCILLARY_USE |
+PNG_FLAG_CRC_ANCILLARY_NOWARN;
+break;
+case PNG_CRC_ERROR_QUIT:                               /* Error/quit */
+png_ptr->flags &= ~PNG_FLAG_CRC_ANCILLARY_MASK;
+png_ptr->flags |= PNG_FLAG_CRC_ANCILLARY_NOWARN;
+break;
+case PNG_CRC_WARN_DISCARD:                      /* Warn/discard data */
+case PNG_CRC_DEFAULT:
+default:
+png_ptr->flags &= ~PNG_FLAG_CRC_ANCILLARY_MASK;
+break;
+}
+}
+#ifdef PNG_READ_TRANSFORMS_SUPPORTED
+/* Is it OK to set a transformation now?  Only if png_start_read_image or
+* png_read_update_info have not been called.  It is not necessary for the IHDR
+* to have been read in all cases, the parameter allows for this check too.
+*/
+static int
+png_rtran_ok(png_structrp png_ptr, int need_IHDR)
+{
+if (png_ptr != NULL)
+{
+if (png_ptr->flags & PNG_FLAG_ROW_INIT)
+png_app_error(png_ptr,
+"invalid after png_start_read_image or png_read_update_info");
+else if (need_IHDR && (png_ptr->mode & PNG_HAVE_IHDR) == 0)
+png_app_error(png_ptr, "invalid before the PNG header has been read");
+else
+{
+/* Turn on failure to initialize correctly for all transforms. */
+png_ptr->flags |= PNG_FLAG_DETECT_UNINITIALIZED;
+return 1; /* Ok */
+}
+}
+return 0; /* no png_error possible! */
+}
+#endif
+#ifdef PNG_READ_BACKGROUND_SUPPORTED
+/* Handle alpha and tRNS via a background color */
+void PNGFAPI
+png_set_background_fixed(png_structrp png_ptr,
+png_const_color_16p background_color, int background_gamma_code,
+int need_expand, png_fixed_point background_gamma)
+{
+png_debug(1, "in png_set_background_fixed");
+if (!png_rtran_ok(png_ptr, 0) || background_color == NULL)
+return;
+if (background_gamma_code == PNG_BACKGROUND_GAMMA_UNKNOWN)
+{
+png_warning(png_ptr, "Application must supply a known background gamma");
+return;
+}
+png_ptr->transformations |= PNG_COMPOSE | PNG_STRIP_ALPHA;
+png_ptr->transformations &= ~PNG_ENCODE_ALPHA;
+png_ptr->flags &= ~PNG_FLAG_OPTIMIZE_ALPHA;
+png_ptr->background = *background_color;
+png_ptr->background_gamma = background_gamma;
+png_ptr->background_gamma_type = (png_byte)(background_gamma_code);
+if (need_expand)
+png_ptr->transformations |= PNG_BACKGROUND_EXPAND;
+else
+png_ptr->transformations &= ~PNG_BACKGROUND_EXPAND;
+}
+#  ifdef PNG_FLOATING_POINT_SUPPORTED
+void PNGAPI
+png_set_background(png_structrp png_ptr,
+png_const_color_16p background_color, int background_gamma_code,
+int need_expand, double background_gamma)
+{
+png_set_background_fixed(png_ptr, background_color, background_gamma_code,
+need_expand, png_fixed(png_ptr, background_gamma, "png_set_background"));
+}
+#  endif  /* FLOATING_POINT */
+#endif /* READ_BACKGROUND */
+/* Scale 16-bit depth files to 8-bit depth.  If both of these are set then the
+* one that pngrtran does first (scale) happens.  This is necessary to allow the
+* TRANSFORM and API behavior to be somewhat consistent, and it's simpler.
+*/
+#ifdef PNG_READ_SCALE_16_TO_8_SUPPORTED
+void PNGAPI
+png_set_scale_16(png_structrp png_ptr)
+{
+png_debug(1, "in png_set_scale_16");
+if (!png_rtran_ok(png_ptr, 0))
+return;
+png_ptr->transformations |= PNG_SCALE_16_TO_8;
+}
+#endif
+#ifdef PNG_READ_STRIP_16_TO_8_SUPPORTED
+/* Chop 16-bit depth files to 8-bit depth */
+void PNGAPI
+png_set_strip_16(png_structrp png_ptr)
+{
+png_debug(1, "in png_set_strip_16");
+if (!png_rtran_ok(png_ptr, 0))
+return;
+png_ptr->transformations |= PNG_16_TO_8;
+}
+#endif
+#ifdef PNG_READ_STRIP_ALPHA_SUPPORTED
+void PNGAPI
+png_set_strip_alpha(png_structrp png_ptr)
+{
+png_debug(1, "in png_set_strip_alpha");
+if (!png_rtran_ok(png_ptr, 0))
+return;
+png_ptr->transformations |= PNG_STRIP_ALPHA;
+}
+#endif
+#if defined(PNG_READ_ALPHA_MODE_SUPPORTED) || defined(PNG_READ_GAMMA_SUPPORTED)
+static png_fixed_point
+translate_gamma_flags(png_structrp png_ptr, png_fixed_point output_gamma,
+int is_screen)
+{
+/* Check for flag values.  The main reason for having the old Mac value as a
+* flag is that it is pretty near impossible to work out what the correct
+* value is from Apple documentation - a working Mac system is needed to
+* discover the value!
+*/
+if (output_gamma == PNG_DEFAULT_sRGB ||
+output_gamma == PNG_FP_1 / PNG_DEFAULT_sRGB)
+{
+/* If there is no sRGB support this just sets the gamma to the standard
+* sRGB value.  (This is a side effect of using this function!)
+*/
+#     ifdef PNG_READ_sRGB_SUPPORTED
+png_ptr->flags |= PNG_FLAG_ASSUME_sRGB;
+#     else
+PNG_UNUSED(png_ptr)
+#     endif
+if (is_screen)
+output_gamma = PNG_GAMMA_sRGB;
+else
+output_gamma = PNG_GAMMA_sRGB_INVERSE;
+}
+else if (output_gamma == PNG_GAMMA_MAC_18 ||
+output_gamma == PNG_FP_1 / PNG_GAMMA_MAC_18)
+{
+if (is_screen)
+output_gamma = PNG_GAMMA_MAC_OLD;
+else
+output_gamma = PNG_GAMMA_MAC_INVERSE;
+}
+return output_gamma;
+}
+#  ifdef PNG_FLOATING_POINT_SUPPORTED
+static png_fixed_point
+convert_gamma_value(png_structrp png_ptr, double output_gamma)
+{
+/* The following silently ignores cases where fixed point (times 100,000)
+* gamma values are passed to the floating point API.  This is safe and it
+* means the fixed point constants work just fine with the floating point
+* API.  The alternative would just lead to undetected errors and spurious
+* bug reports.  Negative values fail inside the _fixed API unless they
+* correspond to the flag values.
+*/
+if (output_gamma > 0 && output_gamma < 128)
+output_gamma *= PNG_FP_1;
+/* This preserves -1 and -2 exactly: */
+output_gamma = floor(output_gamma + .5);
+if (output_gamma > PNG_FP_MAX || output_gamma < PNG_FP_MIN)
+png_fixed_error(png_ptr, "gamma value");
+return (png_fixed_point)output_gamma;
+}
+#  endif
+#endif /* READ_ALPHA_MODE || READ_GAMMA */
+#ifdef PNG_READ_ALPHA_MODE_SUPPORTED
+void PNGFAPI
+png_set_alpha_mode_fixed(png_structrp png_ptr, int mode,
+png_fixed_point output_gamma)
+{
+int compose = 0;
+png_fixed_point file_gamma;
+png_debug(1, "in png_set_alpha_mode");
+if (!png_rtran_ok(png_ptr, 0))
+return;
+output_gamma = translate_gamma_flags(png_ptr, output_gamma, 1/*screen*/);
+/* Validate the value to ensure it is in a reasonable range. The value
+* is expected to be 1 or greater, but this range test allows for some
+* viewing correction values.  The intent is to weed out users of this API
+* who use the inverse of the gamma value accidentally!  Since some of these
+* values are reasonable this may have to be changed.
+*/
+if (output_gamma < 70000 || output_gamma > 300000)
+png_error(png_ptr, "output gamma out of expected range");
+/* The default file gamma is the inverse of the output gamma; the output
+* gamma may be changed below so get the file value first:
+*/
+file_gamma = png_reciprocal(output_gamma);
+/* There are really 8 possibilities here, composed of any combination
+* of:
+*
+*    premultiply the color channels
+*    do not encode non-opaque pixels
+*    encode the alpha as well as the color channels
+*
+* The differences disappear if the input/output ('screen') gamma is 1.0,
+* because then the encoding is a no-op and there is only the choice of
+* premultiplying the color channels or not.
+*
+* png_set_alpha_mode and png_set_background interact because both use
+* png_compose to do the work.  Calling both is only useful when
+* png_set_alpha_mode is used to set the default mode - PNG_ALPHA_PNG - along
+* with a default gamma value.  Otherwise PNG_COMPOSE must not be set.
+*/
+switch (mode)
+{
+case PNG_ALPHA_PNG:        /* default: png standard */
+/* No compose, but it may be set by png_set_background! */
+png_ptr->transformations &= ~PNG_ENCODE_ALPHA;
+png_ptr->flags &= ~PNG_FLAG_OPTIMIZE_ALPHA;
+break;
+case PNG_ALPHA_ASSOCIATED: /* color channels premultiplied */
+compose = 1;
+png_ptr->transformations &= ~PNG_ENCODE_ALPHA;
+png_ptr->flags &= ~PNG_FLAG_OPTIMIZE_ALPHA;
+/* The output is linear: */
+output_gamma = PNG_FP_1;
+break;
+case PNG_ALPHA_OPTIMIZED:  /* associated, non-opaque pixels linear */
+compose = 1;
+png_ptr->transformations &= ~PNG_ENCODE_ALPHA;
+png_ptr->flags |= PNG_FLAG_OPTIMIZE_ALPHA;
+/* output_gamma records the encoding of opaque pixels! */
+break;
+case PNG_ALPHA_BROKEN:     /* associated, non-linear, alpha encoded */
+compose = 1;
+png_ptr->transformations |= PNG_ENCODE_ALPHA;
+png_ptr->flags &= ~PNG_FLAG_OPTIMIZE_ALPHA;
+break;
+default:
+png_error(png_ptr, "invalid alpha mode");
+}
+/* Only set the default gamma if the file gamma has not been set (this has
+* the side effect that the gamma in a second call to png_set_alpha_mode will
+* be ignored.)
+*/
+if (png_ptr->colorspace.gamma == 0)
+{
+png_ptr->colorspace.gamma = file_gamma;
+png_ptr->colorspace.flags |= PNG_COLORSPACE_HAVE_GAMMA;
+}
+/* But always set the output gamma: */
+png_ptr->screen_gamma = output_gamma;
+/* Finally, if pre-multiplying, set the background fields to achieve the
+* desired result.
+*/
+if (compose)
+{
+/* And obtain alpha pre-multiplication by composing on black: */
+memset(&png_ptr->background, 0, (sizeof png_ptr->background));
+png_ptr->background_gamma = png_ptr->colorspace.gamma; /* just in case */
+png_ptr->background_gamma_type = PNG_BACKGROUND_GAMMA_FILE;
+png_ptr->transformations &= ~PNG_BACKGROUND_EXPAND;
+if (png_ptr->transformations & PNG_COMPOSE)
+png_error(png_ptr,
+"conflicting calls to set alpha mode and background");
+png_ptr->transformations |= PNG_COMPOSE;
+}
+}
+#  ifdef PNG_FLOATING_POINT_SUPPORTED
+void PNGAPI
+png_set_alpha_mode(png_structrp png_ptr, int mode, double output_gamma)
+{
+png_set_alpha_mode_fixed(png_ptr, mode, convert_gamma_value(png_ptr,
+output_gamma));
+}
+#  endif
+#endif
+#ifdef PNG_READ_QUANTIZE_SUPPORTED
+/* Dither file to 8-bit.  Supply a palette, the current number
+* of elements in the palette, the maximum number of elements
+* allowed, and a histogram if possible.  If the current number
+* of colors is greater then the maximum number, the palette will be
+* modified to fit in the maximum number.  "full_quantize" indicates
+* whether we need a quantizing cube set up for RGB images, or if we
+* simply are reducing the number of colors in a paletted image.
+*/
+typedef struct png_dsort_struct
+{
+struct png_dsort_struct * next;
+png_byte left;
+png_byte right;
+} png_dsort;
+typedef png_dsort *   png_dsortp;
+typedef png_dsort * * png_dsortpp;
+void PNGAPI
+png_set_quantize(png_structrp png_ptr, png_colorp palette,
+int num_palette, int maximum_colors, png_const_uint_16p histogram,
+int full_quantize)
+{
+png_debug(1, "in png_set_quantize");
+if (!png_rtran_ok(png_ptr, 0))
+return;
+png_ptr->transformations |= PNG_QUANTIZE;
+if (!full_quantize)
+{
+int i;
+png_ptr->quantize_index = (png_bytep)png_malloc(png_ptr,
+(png_uint_32)(num_palette * (sizeof (png_byte))));
+for (i = 0; i < num_palette; i++)
+png_ptr->quantize_index[i] = (png_byte)i;
+}
+if (num_palette > maximum_colors)
+{
+if (histogram != NULL)
+{
+/* This is easy enough, just throw out the least used colors.
+* Perhaps not the best solution, but good enough.
+*/
+int i;
+/* Initialize an array to sort colors */
+png_ptr->quantize_sort = (png_bytep)png_malloc(png_ptr,
+(png_uint_32)(num_palette * (sizeof (png_byte))));
+/* Initialize the quantize_sort array */
+for (i = 0; i < num_palette; i++)
+png_ptr->quantize_sort[i] = (png_byte)i;
+/* Find the least used palette entries by starting a
+* bubble sort, and running it until we have sorted
+* out enough colors.  Note that we don't care about
+* sorting all the colors, just finding which are
+* least used.
+*/
+for (i = num_palette - 1; i >= maximum_colors; i--)
+{
+int done; /* To stop early if the list is pre-sorted */
+int j;
+done = 1;
+for (j = 0; j < i; j++)
+{
+if (histogram[png_ptr->quantize_sort[j]]
+< histogram[png_ptr->quantize_sort[j + 1]])
+{
+png_byte t;
+t = png_ptr->quantize_sort[j];
+png_ptr->quantize_sort[j] = png_ptr->quantize_sort[j + 1];
+png_ptr->quantize_sort[j + 1] = t;
+done = 0;
+}
+}
+if (done)
+break;
+}
+/* Swap the palette around, and set up a table, if necessary */
+if (full_quantize)
+{
+int j = num_palette;
+/* Put all the useful colors within the max, but don't
+* move the others.
+*/
+for (i = 0; i < maximum_colors; i++)
+{
+if ((int)png_ptr->quantize_sort[i] >= maximum_colors)
+{
+do
+j--;
+while ((int)png_ptr->quantize_sort[j] >= maximum_colors);
+palette[i] = palette[j];
+}
+}
+}
+else
+{
+int j = num_palette;
+/* Move all the used colors inside the max limit, and
+* develop a translation table.
+*/
+for (i = 0; i < maximum_colors; i++)
+{
+/* Only move the colors we need to */
+if ((int)png_ptr->quantize_sort[i] >= maximum_colors)
+{
+png_color tmp_color;
+do
+j--;
+while ((int)png_ptr->quantize_sort[j] >= maximum_colors);
+tmp_color = palette[j];
+palette[j] = palette[i];
+palette[i] = tmp_color;
+/* Indicate where the color went */
+png_ptr->quantize_index[j] = (png_byte)i;
+png_ptr->quantize_index[i] = (png_byte)j;
+}
+}
+/* Find closest color for those colors we are not using */
+for (i = 0; i < num_palette; i++)
+{
+if ((int)png_ptr->quantize_index[i] >= maximum_colors)
+{
+int min_d, k, min_k, d_index;
+/* Find the closest color to one we threw out */
+d_index = png_ptr->quantize_index[i];
+min_d = PNG_COLOR_DIST(palette[d_index], palette[0]);
+for (k = 1, min_k = 0; k < maximum_colors; k++)
+{
+int d;
+d = PNG_COLOR_DIST(palette[d_index], palette[k]);
+if (d < min_d)
+{
+min_d = d;
+min_k = k;
+}
+}
+/* Point to closest color */
+png_ptr->quantize_index[i] = (png_byte)min_k;
+}
+}
+}
+png_free(png_ptr, png_ptr->quantize_sort);
+png_ptr->quantize_sort = NULL;
+}
+else
+{
+/* This is much harder to do simply (and quickly).  Perhaps
+* we need to go through a median cut routine, but those
+* don't always behave themselves with only a few colors
+* as input.  So we will just find the closest two colors,
+* and throw out one of them (chosen somewhat randomly).
+* [We don't understand this at all, so if someone wants to
+*  work on improving it, be our guest - AED, GRP]
+*/
+int i;
+int max_d;
+int num_new_palette;
+png_dsortp t;
+png_dsortpp hash;
+t = NULL;
+/* Initialize palette index arrays */
+png_ptr->index_to_palette = (png_bytep)png_malloc(png_ptr,
+(png_uint_32)(num_palette * (sizeof (png_byte))));
+png_ptr->palette_to_index = (png_bytep)png_malloc(png_ptr,
+(png_uint_32)(num_palette * (sizeof (png_byte))));
+/* Initialize the sort array */
+for (i = 0; i < num_palette; i++)
+{
+png_ptr->index_to_palette[i] = (png_byte)i;
+png_ptr->palette_to_index[i] = (png_byte)i;
+}
+hash = (png_dsortpp)png_calloc(png_ptr, (png_uint_32)(769 *
+(sizeof (png_dsortp))));
+num_new_palette = num_palette;
+/* Initial wild guess at how far apart the farthest pixel
+* pair we will be eliminating will be.  Larger
+* numbers mean more areas will be allocated, Smaller
+* numbers run the risk of not saving enough data, and
+* having to do this all over again.
+*
+* I have not done extensive checking on this number.
+*/
+max_d = 96;
+while (num_new_palette > maximum_colors)
+{
+for (i = 0; i < num_new_palette - 1; i++)
+{
+int j;
+for (j = i + 1; j < num_new_palette; j++)
+{
+int d;
+d = PNG_COLOR_DIST(palette[i], palette[j]);
+if (d <= max_d)
+{
+t = (png_dsortp)png_malloc_warn(png_ptr,
+(png_uint_32)(sizeof (png_dsort)));
+if (t == NULL)
+break;
+t->next = hash[d];
+t->left = (png_byte)i;
+t->right = (png_byte)j;
+hash[d] = t;
+}
+}
+if (t == NULL)
+break;
+}
+if (t != NULL)
+for (i = 0; i <= max_d; i++)
+{
+if (hash[i] != NULL)
+{
+png_dsortp p;
+for (p = hash[i]; p; p = p->next)
+{
+if ((int)png_ptr->index_to_palette[p->left]
+< num_new_palette &&
+(int)png_ptr->index_to_palette[p->right]
+< num_new_palette)
+{
+int j, next_j;
+if (num_new_palette & 0x01)
+{
+j = p->left;
+next_j = p->right;
+}
+else
+{
+j = p->right;
+next_j = p->left;
+}
+num_new_palette--;
+palette[png_ptr->index_to_palette[j]]
+= palette[num_new_palette];
+if (!full_quantize)
+{
+int k;
+for (k = 0; k < num_palette; k++)
+{
+if (png_ptr->quantize_index[k] ==
+png_ptr->index_to_palette[j])
+png_ptr->quantize_index[k] =
+png_ptr->index_to_palette[next_j];
+if ((int)png_ptr->quantize_index[k] ==
+num_new_palette)
+png_ptr->quantize_index[k] =
+png_ptr->index_to_palette[j];
+}
+}
+png_ptr->index_to_palette[png_ptr->palette_to_index
+[num_new_palette]] = png_ptr->index_to_palette[j];
+png_ptr->palette_to_index[png_ptr->index_to_palette[j]]
+= png_ptr->palette_to_index[num_new_palette];
+png_ptr->index_to_palette[j] =
+(png_byte)num_new_palette;
+png_ptr->palette_to_index[num_new_palette] =
+(png_byte)j;
+}
+if (num_new_palette <= maximum_colors)
+break;
+}
+if (num_new_palette <= maximum_colors)
+break;
+}
+}
+for (i = 0; i < 769; i++)
+{
+if (hash[i] != NULL)
+{
+png_dsortp p = hash[i];
+while (p)
+{
+t = p->next;
+png_free(png_ptr, p);
+p = t;
+}
+}
+hash[i] = 0;
+}
+max_d += 96;
+}
+png_free(png_ptr, hash);
+png_free(png_ptr, png_ptr->palette_to_index);
+png_free(png_ptr, png_ptr->index_to_palette);
+png_ptr->palette_to_index = NULL;
+png_ptr->index_to_palette = NULL;
+}
+num_palette = maximum_colors;
+}
+if (png_ptr->palette == NULL)
+{
+png_ptr->palette = palette;
+}
+png_ptr->num_palette = (png_uint_16)num_palette;
+if (full_quantize)
+{
+int i;
+png_bytep distance;
+int total_bits = PNG_QUANTIZE_RED_BITS + PNG_QUANTIZE_GREEN_BITS +
+PNG_QUANTIZE_BLUE_BITS;
+int num_red = (1 << PNG_QUANTIZE_RED_BITS);
+int num_green = (1 << PNG_QUANTIZE_GREEN_BITS);
+int num_blue = (1 << PNG_QUANTIZE_BLUE_BITS);
+png_size_t num_entries = ((png_size_t)1 << total_bits);
+png_ptr->palette_lookup = (png_bytep)png_calloc(png_ptr,
+(png_uint_32)(num_entries * (sizeof (png_byte))));
+distance = (png_bytep)png_malloc(png_ptr, (png_uint_32)(num_entries *
+(sizeof (png_byte))));
+memset(distance, 0xff, num_entries * (sizeof (png_byte)));
+for (i = 0; i < num_palette; i++)
+{
+int ir, ig, ib;
+int r = (palette[i].red >> (8 - PNG_QUANTIZE_RED_BITS));
+int g = (palette[i].green >> (8 - PNG_QUANTIZE_GREEN_BITS));
+int b = (palette[i].blue >> (8 - PNG_QUANTIZE_BLUE_BITS));
+for (ir = 0; ir < num_red; ir++)
+{
+/* int dr = abs(ir - r); */
+int dr = ((ir > r) ? ir - r : r - ir);
+int index_r = (ir << (PNG_QUANTIZE_BLUE_BITS +
+PNG_QUANTIZE_GREEN_BITS));
+for (ig = 0; ig < num_green; ig++)
+{
+/* int dg = abs(ig - g); */
+int dg = ((ig > g) ? ig - g : g - ig);
+int dt = dr + dg;
+int dm = ((dr > dg) ? dr : dg);
+int index_g = index_r | (ig << PNG_QUANTIZE_BLUE_BITS);
+for (ib = 0; ib < num_blue; ib++)
+{
+int d_index = index_g | ib;
+/* int db = abs(ib - b); */
+int db = ((ib > b) ? ib - b : b - ib);
+int dmax = ((dm > db) ? dm : db);
+int d = dmax + dt + db;
+if (d < (int)distance[d_index])
+{
+distance[d_index] = (png_byte)d;
+png_ptr->palette_lookup[d_index] = (png_byte)i;
+}
+}
+}
+}
+}
+png_free(png_ptr, distance);
+}
+}
+#endif /* PNG_READ_QUANTIZE_SUPPORTED */
+#ifdef PNG_READ_GAMMA_SUPPORTED
+void PNGFAPI
+png_set_gamma_fixed(png_structrp png_ptr, png_fixed_point scrn_gamma,
+png_fixed_point file_gamma)
+{
+png_debug(1, "in png_set_gamma_fixed");
+if (!png_rtran_ok(png_ptr, 0))
+return;
+/* New in libpng-1.5.4 - reserve particular negative values as flags. */
+scrn_gamma = translate_gamma_flags(png_ptr, scrn_gamma, 1/*screen*/);
+file_gamma = translate_gamma_flags(png_ptr, file_gamma, 0/*file*/);
+/* Checking the gamma values for being >0 was added in 1.5.4 along with the
+* premultiplied alpha support; this actually hides an undocumented feature
+* of the previous implementation which allowed gamma processing to be
+* disabled in background handling.  There is no evidence (so far) that this
+* was being used; however, png_set_background itself accepted and must still
+* accept '0' for the gamma value it takes, because it isn't always used.
+*
+* Since this is an API change (albeit a very minor one that removes an
+* undocumented API feature) the following checks were only enabled in
+* libpng-1.6.0.
+*/
+if (file_gamma <= 0)
+png_error(png_ptr, "invalid file gamma in png_set_gamma");
+if (scrn_gamma <= 0)
+png_error(png_ptr, "invalid screen gamma in png_set_gamma");
+/* Set the gamma values unconditionally - this overrides the value in the PNG
+* file if a gAMA chunk was present.  png_set_alpha_mode provides a
+* different, easier, way to default the file gamma.
+*/
+png_ptr->colorspace.gamma = file_gamma;
+png_ptr->colorspace.flags |= PNG_COLORSPACE_HAVE_GAMMA;
+png_ptr->screen_gamma = scrn_gamma;
+}
+#  ifdef PNG_FLOATING_POINT_SUPPORTED
+void PNGAPI
+png_set_gamma(png_structrp png_ptr, double scrn_gamma, double file_gamma)
+{
+png_set_gamma_fixed(png_ptr, convert_gamma_value(png_ptr, scrn_gamma),
+convert_gamma_value(png_ptr, file_gamma));
+}
+#  endif /* FLOATING_POINT_SUPPORTED */
+#endif /* READ_GAMMA */
+#ifdef PNG_READ_EXPAND_SUPPORTED
+/* Expand paletted images to RGB, expand grayscale images of
+* less than 8-bit depth to 8-bit depth, and expand tRNS chunks
+* to alpha channels.
+*/
+void PNGAPI
+png_set_expand(png_structrp png_ptr)
+{
+png_debug(1, "in png_set_expand");
+if (!png_rtran_ok(png_ptr, 0))
+return;
+png_ptr->transformations |= (PNG_EXPAND | PNG_EXPAND_tRNS);
+}
+/* GRR 19990627:  the following three functions currently are identical
+*  to png_set_expand().  However, it is entirely reasonable that someone
+*  might wish to expand an indexed image to RGB but *not* expand a single,
+*  fully transparent palette entry to a full alpha channel--perhaps instead
+*  convert tRNS to the grayscale/RGB format (16-bit RGB value), or replace
+*  the transparent color with a particular RGB value, or drop tRNS entirely.
+*  IOW, a future version of the library may make the transformations flag
+*  a bit more fine-grained, with separate bits for each of these three
+*  functions.
+*
+*  More to the point, these functions make it obvious what libpng will be
+*  doing, whereas "expand" can (and does) mean any number of things.
+*
+*  GRP 20060307: In libpng-1.2.9, png_set_gray_1_2_4_to_8() was modified
+*  to expand only the sample depth but not to expand the tRNS to alpha
+*  and its name was changed to png_set_expand_gray_1_2_4_to_8().
+*/
+/* Expand paletted images to RGB. */
+void PNGAPI
+png_set_palette_to_rgb(png_structrp png_ptr)
+{
+png_debug(1, "in png_set_palette_to_rgb");
+if (!png_rtran_ok(png_ptr, 0))
+return;
+png_ptr->transformations |= (PNG_EXPAND | PNG_EXPAND_tRNS);
+}
+/* Expand grayscale images of less than 8-bit depth to 8 bits. */
+void PNGAPI
+png_set_expand_gray_1_2_4_to_8(png_structrp png_ptr)
+{
+png_debug(1, "in png_set_expand_gray_1_2_4_to_8");
+if (!png_rtran_ok(png_ptr, 0))
+return;
+png_ptr->transformations |= PNG_EXPAND;
+}
+/* Expand tRNS chunks to alpha channels. */
+void PNGAPI
+png_set_tRNS_to_alpha(png_structrp png_ptr)
+{
+png_debug(1, "in png_set_tRNS_to_alpha");
+if (!png_rtran_ok(png_ptr, 0))
+return;
+png_ptr->transformations |= (PNG_EXPAND | PNG_EXPAND_tRNS);
+}
+#endif /* defined(PNG_READ_EXPAND_SUPPORTED) */
+#ifdef PNG_READ_EXPAND_16_SUPPORTED
+/* Expand to 16-bit channels, expand the tRNS chunk too (because otherwise
+* it may not work correctly.)
+*/
+void PNGAPI
+png_set_expand_16(png_structrp png_ptr)
+{
+png_debug(1, "in png_set_expand_16");
+if (!png_rtran_ok(png_ptr, 0))
+return;
+png_ptr->transformations |= (PNG_EXPAND_16 | PNG_EXPAND | PNG_EXPAND_tRNS);
+}
+#endif
+#ifdef PNG_READ_GRAY_TO_RGB_SUPPORTED
+void PNGAPI
+png_set_gray_to_rgb(png_structrp png_ptr)
+{
+png_debug(1, "in png_set_gray_to_rgb");
+if (!png_rtran_ok(png_ptr, 0))
+return;
+/* Because rgb must be 8 bits or more: */
+png_set_expand_gray_1_2_4_to_8(png_ptr);
+png_ptr->transformations |= PNG_GRAY_TO_RGB;
+}
+#endif
+#ifdef PNG_READ_RGB_TO_GRAY_SUPPORTED
+void PNGFAPI
+png_set_rgb_to_gray_fixed(png_structrp png_ptr, int error_action,
+png_fixed_point red, png_fixed_point green)
+{
+png_debug(1, "in png_set_rgb_to_gray");
+/* Need the IHDR here because of the check on color_type below. */
+/* TODO: fix this */
+if (!png_rtran_ok(png_ptr, 1))
+return;
+switch(error_action)
+{
+case PNG_ERROR_ACTION_NONE:
+png_ptr->transformations |= PNG_RGB_TO_GRAY;
+break;
+case PNG_ERROR_ACTION_WARN:
+png_ptr->transformations |= PNG_RGB_TO_GRAY_WARN;
+break;
+case PNG_ERROR_ACTION_ERROR:
+png_ptr->transformations |= PNG_RGB_TO_GRAY_ERR;
+break;
+default:
+png_error(png_ptr, "invalid error action to rgb_to_gray");
+break;
+}
+if (png_ptr->color_type == PNG_COLOR_TYPE_PALETTE)
+#ifdef PNG_READ_EXPAND_SUPPORTED
+png_ptr->transformations |= PNG_EXPAND;
+#else
+{
+/* Make this an error in 1.6 because otherwise the application may assume
+* that it just worked and get a memory overwrite.
+*/
+png_error(png_ptr,
+"Cannot do RGB_TO_GRAY without EXPAND_SUPPORTED");
+/* png_ptr->transformations &= ~PNG_RGB_TO_GRAY; */
+}
+#endif
+{
+if (red >= 0 && green >= 0 && red + green <= PNG_FP_1)
+{
+png_uint_16 red_int, green_int;
+/* NOTE: this calculation does not round, but this behavior is retained
+* for consistency, the inaccuracy is very small.  The code here always
+* overwrites the coefficients, regardless of whether they have been
+* defaulted or set already.
+*/
+red_int = (png_uint_16)(((png_uint_32)red*32768)/100000);
+green_int = (png_uint_16)(((png_uint_32)green*32768)/100000);
+png_ptr->rgb_to_gray_red_coeff   = red_int;
+png_ptr->rgb_to_gray_green_coeff = green_int;
+png_ptr->rgb_to_gray_coefficients_set = 1;
+}
+else
+{
+if (red >= 0 && green >= 0)
+png_app_warning(png_ptr,
+"ignoring out of range rgb_to_gray coefficients");
+/* Use the defaults, from the cHRM chunk if set, else the historical
+* values which are close to the sRGB/HDTV/ITU-Rec 709 values.  See
+* png_do_rgb_to_gray for more discussion of the values.  In this case
+* the coefficients are not marked as 'set' and are not overwritten if
+* something has already provided a default.
+*/
+if (png_ptr->rgb_to_gray_red_coeff == 0 &&
+png_ptr->rgb_to_gray_green_coeff == 0)
+{
+png_ptr->rgb_to_gray_red_coeff   = 6968;
+png_ptr->rgb_to_gray_green_coeff = 23434;
+/* png_ptr->rgb_to_gray_blue_coeff  = 2366; */
+}
+}
+}
+}
+#ifdef PNG_FLOATING_POINT_SUPPORTED
+/* Convert a RGB image to a grayscale of the same width.  This allows us,
+* for example, to convert a 24 bpp RGB image into an 8 bpp grayscale image.
+*/
+void PNGAPI
+png_set_rgb_to_gray(png_structrp png_ptr, int error_action, double red,
+double green)
+{
+png_set_rgb_to_gray_fixed(png_ptr, error_action,
+png_fixed(png_ptr, red, "rgb to gray red coefficient"),
+png_fixed(png_ptr, green, "rgb to gray green coefficient"));
+}
+#endif /* FLOATING POINT */
+#endif /* RGB_TO_GRAY */
+#if defined(PNG_READ_USER_TRANSFORM_SUPPORTED) || \
+defined(PNG_WRITE_USER_TRANSFORM_SUPPORTED)
+void PNGAPI
+png_set_read_user_transform_fn(png_structrp png_ptr, png_user_transform_ptr
+read_user_transform_fn)
+{
+png_debug(1, "in png_set_read_user_transform_fn");
+#ifdef PNG_READ_USER_TRANSFORM_SUPPORTED
+png_ptr->transformations |= PNG_USER_TRANSFORM;
+png_ptr->read_user_transform_fn = read_user_transform_fn;
+#endif
+}
+#endif
+#ifdef PNG_READ_TRANSFORMS_SUPPORTED
+#ifdef PNG_READ_GAMMA_SUPPORTED
+/* In the case of gamma transformations only do transformations on images where
+* the [file] gamma and screen_gamma are not close reciprocals, otherwise it
+* slows things down slightly, and also needlessly introduces small errors.
+*/
+static int /* PRIVATE */
+png_gamma_threshold(png_fixed_point screen_gamma, png_fixed_point file_gamma)
+{
+/* PNG_GAMMA_THRESHOLD is the threshold for performing gamma
+* correction as a difference of the overall transform from 1.0
+*
+* We want to compare the threshold with s*f - 1, if we get
+* overflow here it is because of wacky gamma values so we
+* turn on processing anyway.
+*/
+png_fixed_point gtest;
+return !png_muldiv(&gtest, screen_gamma, file_gamma, PNG_FP_1) ||
+png_gamma_significant(gtest);
+}
+#endif
+/* Initialize everything needed for the read.  This includes modifying
+* the palette.
+*/
+/*For the moment 'png_init_palette_transformations' and
+* 'png_init_rgb_transformations' only do some flag canceling optimizations.
+* The intent is that these two routines should have palette or rgb operations
+* extracted from 'png_init_read_transformations'.
+*/
+static void /* PRIVATE */
+png_init_palette_transformations(png_structrp png_ptr)
+{
+/* Called to handle the (input) palette case.  In png_do_read_transformations
+* the first step is to expand the palette if requested, so this code must
+* take care to only make changes that are invariant with respect to the
+* palette expansion, or only do them if there is no expansion.
+*
+* STRIP_ALPHA has already been handled in the caller (by setting num_trans
+* to 0.)
+*/
+int input_has_alpha = 0;
+int input_has_transparency = 0;
+if (png_ptr->num_trans > 0)
+{
+int i;
+/* Ignore if all the entries are opaque (unlikely!) */
+for (i=0; i<png_ptr->num_trans; ++i)
+{
+if (png_ptr->trans_alpha[i] == 255)
+continue;
+else if (png_ptr->trans_alpha[i] == 0)
+input_has_transparency = 1;
+else
+{
+input_has_transparency = 1;
+input_has_alpha = 1;
+break;
+}
+}
+}
+/* If no alpha we can optimize. */
+if (!input_has_alpha)
+{
+/* Any alpha means background and associative alpha processing is
+* required, however if the alpha is 0 or 1 throughout OPTIMIZE_ALPHA
+* and ENCODE_ALPHA are irrelevant.
+*/
+png_ptr->transformations &= ~PNG_ENCODE_ALPHA;
+png_ptr->flags &= ~PNG_FLAG_OPTIMIZE_ALPHA;
+if (!input_has_transparency)
+png_ptr->transformations &= ~(PNG_COMPOSE | PNG_BACKGROUND_EXPAND);
+}
+#if defined(PNG_READ_EXPAND_SUPPORTED) && defined(PNG_READ_BACKGROUND_SUPPORTED)
+/* png_set_background handling - deals with the complexity of whether the
+* background color is in the file format or the screen format in the case
+* where an 'expand' will happen.
+*/
+/* The following code cannot be entered in the alpha pre-multiplication case
+* because PNG_BACKGROUND_EXPAND is cancelled below.
+*/
+if ((png_ptr->transformations & PNG_BACKGROUND_EXPAND) &&
+(png_ptr->transformations & PNG_EXPAND))
+{
+{
+png_ptr->background.red   =
+png_ptr->palette[png_ptr->background.index].red;
+png_ptr->background.green =
+png_ptr->palette[png_ptr->background.index].green;
+png_ptr->background.blue  =
+png_ptr->palette[png_ptr->background.index].blue;
+#ifdef PNG_READ_INVERT_ALPHA_SUPPORTED
+if (png_ptr->transformations & PNG_INVERT_ALPHA)
+{
+if (!(png_ptr->transformations & PNG_EXPAND_tRNS))
+{
+/* Invert the alpha channel (in tRNS) unless the pixels are
+* going to be expanded, in which case leave it for later
+*/
+int i, istop = png_ptr->num_trans;
+for (i=0; i<istop; i++)
+png_ptr->trans_alpha[i] = (png_byte)(255 -
+png_ptr->trans_alpha[i]);
+}
+}
+#endif /* PNG_READ_INVERT_ALPHA_SUPPORTED */
+}
+} /* background expand and (therefore) no alpha association. */
+#endif /* PNG_READ_EXPAND_SUPPORTED && PNG_READ_BACKGROUND_SUPPORTED */
+}
+static void /* PRIVATE */
+png_init_rgb_transformations(png_structrp png_ptr)
+{
+/* Added to libpng-1.5.4: check the color type to determine whether there
+* is any alpha or transparency in the image and simply cancel the
+* background and alpha mode stuff if there isn't.
+*/
+int input_has_alpha = (png_ptr->color_type & PNG_COLOR_MASK_ALPHA) != 0;
+int input_has_transparency = png_ptr->num_trans > 0;
+/* If no alpha we can optimize. */
+if (!input_has_alpha)
+{
+/* Any alpha means background and associative alpha processing is
+* required, however if the alpha is 0 or 1 throughout OPTIMIZE_ALPHA
+* and ENCODE_ALPHA are irrelevant.
+*/
+#     ifdef PNG_READ_ALPHA_MODE_SUPPORTED
+png_ptr->transformations &= ~PNG_ENCODE_ALPHA;
+png_ptr->flags &= ~PNG_FLAG_OPTIMIZE_ALPHA;
+#     endif
+if (!input_has_transparency)
+png_ptr->transformations &= ~(PNG_COMPOSE | PNG_BACKGROUND_EXPAND);
+}
+#if defined(PNG_READ_EXPAND_SUPPORTED) && defined(PNG_READ_BACKGROUND_SUPPORTED)
+/* png_set_background handling - deals with the complexity of whether the
+* background color is in the file format or the screen format in the case
+* where an 'expand' will happen.
+*/
+/* The following code cannot be entered in the alpha pre-multiplication case
+* because PNG_BACKGROUND_EXPAND is cancelled below.
+*/
+if ((png_ptr->transformations & PNG_BACKGROUND_EXPAND) &&
+(png_ptr->transformations & PNG_EXPAND) &&
+!(png_ptr->color_type & PNG_COLOR_MASK_COLOR))
+/* i.e., GRAY or GRAY_ALPHA */
+{
+{
+/* Expand background and tRNS chunks */
+int gray = png_ptr->background.gray;
+int trans_gray = png_ptr->trans_color.gray;
+switch (png_ptr->bit_depth)
+{
+case 1:
+gray *= 0xff;
+trans_gray *= 0xff;
+break;
+case 2:
+gray *= 0x55;
+trans_gray *= 0x55;
+break;
+case 4:
+gray *= 0x11;
+trans_gray *= 0x11;
+break;
+default:
+case 8:
+/* FALL THROUGH (Already 8 bits) */
+case 16:
+/* Already a full 16 bits */
+break;
+}
+png_ptr->background.red = png_ptr->background.green =
+png_ptr->background.blue = (png_uint_16)gray;
+if (!(png_ptr->transformations & PNG_EXPAND_tRNS))
+{
+png_ptr->trans_color.red = png_ptr->trans_color.green =
+png_ptr->trans_color.blue = (png_uint_16)trans_gray;
+}
+}
+} /* background expand and (therefore) no alpha association. */
+#endif /* PNG_READ_EXPAND_SUPPORTED && PNG_READ_BACKGROUND_SUPPORTED */
+}
+void /* PRIVATE */
+png_init_read_transformations(png_structrp png_ptr)
+{
+png_debug(1, "in png_init_read_transformations");
+/* This internal function is called from png_read_start_row in pngrutil.c
+* and it is called before the 'rowbytes' calculation is done, so the code
+* in here can change or update the transformations flags.
+*
+* First do updates that do not depend on the details of the PNG image data
+* being processed.
+*/
+#ifdef PNG_READ_GAMMA_SUPPORTED
+/* Prior to 1.5.4 these tests were performed from png_set_gamma, 1.5.4 adds
+* png_set_alpha_mode and this is another source for a default file gamma so
+* the test needs to be performed later - here.  In addition prior to 1.5.4
+* the tests were repeated for the PALETTE color type here - this is no
+* longer necessary (and doesn't seem to have been necessary before.)
+*/
+{
+/* The following temporary indicates if overall gamma correction is
+* required.
+*/
+int gamma_correction = 0;
+if (png_ptr->colorspace.gamma != 0) /* has been set */
+{
+if (png_ptr->screen_gamma != 0) /* screen set too */
+gamma_correction = png_gamma_threshold(png_ptr->colorspace.gamma,
+png_ptr->screen_gamma);
+else
+/* Assume the output matches the input; a long time default behavior
+* of libpng, although the standard has nothing to say about this.
+*/
+png_ptr->screen_gamma = png_reciprocal(png_ptr->colorspace.gamma);
+}
+else if (png_ptr->screen_gamma != 0)
+/* The converse - assume the file matches the screen, note that this
+* perhaps undesireable default can (from 1.5.4) be changed by calling
+* png_set_alpha_mode (even if the alpha handling mode isn't required
+* or isn't changed from the default.)
+*/
+png_ptr->colorspace.gamma = png_reciprocal(png_ptr->screen_gamma);
+else /* neither are set */
+/* Just in case the following prevents any processing - file and screen
+* are both assumed to be linear and there is no way to introduce a
+* third gamma value other than png_set_background with 'UNIQUE', and,
+* prior to 1.5.4
+*/
+png_ptr->screen_gamma = png_ptr->colorspace.gamma = PNG_FP_1;
+/* We have a gamma value now. */
+png_ptr->colorspace.flags |= PNG_COLORSPACE_HAVE_GAMMA;
+/* Now turn the gamma transformation on or off as appropriate.  Notice
+* that PNG_GAMMA just refers to the file->screen correction.  Alpha
+* composition may independently cause gamma correction because it needs
+* linear data (e.g. if the file has a gAMA chunk but the screen gamma
+* hasn't been specified.)  In any case this flag may get turned off in
+* the code immediately below if the transform can be handled outside the
+* row loop.
+*/
+if (gamma_correction)
+png_ptr->transformations |= PNG_GAMMA;
+else
+png_ptr->transformations &= ~PNG_GAMMA;
+}
+#endif
+/* Certain transformations have the effect of preventing other
+* transformations that happen afterward in png_do_read_transformations,
+* resolve the interdependencies here.  From the code of
+* png_do_read_transformations the order is:
+*
+*  1) PNG_EXPAND (including PNG_EXPAND_tRNS)
+*  2) PNG_STRIP_ALPHA (if no compose)
+*  3) PNG_RGB_TO_GRAY
+*  4) PNG_GRAY_TO_RGB iff !PNG_BACKGROUND_IS_GRAY
+*  5) PNG_COMPOSE
+*  6) PNG_GAMMA
+*  7) PNG_STRIP_ALPHA (if compose)
+*  8) PNG_ENCODE_ALPHA
+*  9) PNG_SCALE_16_TO_8
+* 10) PNG_16_TO_8
+* 11) PNG_QUANTIZE (converts to palette)
+* 12) PNG_EXPAND_16
+* 13) PNG_GRAY_TO_RGB iff PNG_BACKGROUND_IS_GRAY
+* 14) PNG_INVERT_MONO
+* 15) PNG_INVERT_ALPHA
+* 16) PNG_SHIFT
+* 17) PNG_PACK
+* 18) PNG_BGR
+* 19) PNG_PACKSWAP
+* 20) PNG_FILLER (includes PNG_ADD_ALPHA)
+* 21) PNG_SWAP_ALPHA
+* 22) PNG_SWAP_BYTES
+* 23) PNG_USER_TRANSFORM [must be last]
+*/
+#ifdef PNG_READ_STRIP_ALPHA_SUPPORTED
+if ((png_ptr->transformations & PNG_STRIP_ALPHA) &&
+!(png_ptr->transformations & PNG_COMPOSE))
+{
+/* Stripping the alpha channel happens immediately after the 'expand'
+* transformations, before all other transformation, so it cancels out
+* the alpha handling.  It has the side effect negating the effect of
+* PNG_EXPAND_tRNS too:
+*/
+png_ptr->transformations &= ~(PNG_BACKGROUND_EXPAND | PNG_ENCODE_ALPHA |
+PNG_EXPAND_tRNS);
+png_ptr->flags &= ~PNG_FLAG_OPTIMIZE_ALPHA;
+/* Kill the tRNS chunk itself too.  Prior to 1.5.4 this did not happen
+* so transparency information would remain just so long as it wasn't
+* expanded.  This produces unexpected API changes if the set of things
+* that do PNG_EXPAND_tRNS changes (perfectly possible given the
+* documentation - which says ask for what you want, accept what you
+* get.)  This makes the behavior consistent from 1.5.4:
+*/
+png_ptr->num_trans = 0;
+}
+#endif /* STRIP_ALPHA supported, no COMPOSE */
+#ifdef PNG_READ_ALPHA_MODE_SUPPORTED
+/* If the screen gamma is about 1.0 then the OPTIMIZE_ALPHA and ENCODE_ALPHA
+* settings will have no effect.
+*/
+if (!png_gamma_significant(png_ptr->screen_gamma))
+{
+png_ptr->transformations &= ~PNG_ENCODE_ALPHA;
+png_ptr->flags &= ~PNG_FLAG_OPTIMIZE_ALPHA;
+}
+#endif
+#ifdef PNG_READ_RGB_TO_GRAY_SUPPORTED
+/* Make sure the coefficients for the rgb to gray conversion are set
+* appropriately.
+*/
+if (png_ptr->transformations & PNG_RGB_TO_GRAY)
+png_colorspace_set_rgb_coefficients(png_ptr);
+#endif
+#ifdef PNG_READ_GRAY_TO_RGB_SUPPORTED
+#if defined(PNG_READ_EXPAND_SUPPORTED) && defined(PNG_READ_BACKGROUND_SUPPORTED)
+/* Detect gray background and attempt to enable optimization for
+* gray --> RGB case.
+*
+* Note:  if PNG_BACKGROUND_EXPAND is set and color_type is either RGB or
+* RGB_ALPHA (in which case need_expand is superfluous anyway), the
+* background color might actually be gray yet not be flagged as such.
+* This is not a problem for the current code, which uses
+* PNG_BACKGROUND_IS_GRAY only to decide when to do the
+* png_do_gray_to_rgb() transformation.
+*
+* TODO: this code needs to be revised to avoid the complexity and
+* interdependencies.  The color type of the background should be recorded in
+* png_set_background, along with the bit depth, then the code has a record
+* of exactly what color space the background is currently in.
+*/
+if (png_ptr->transformations & PNG_BACKGROUND_EXPAND)
+{
+/* PNG_BACKGROUND_EXPAND: the background is in the file color space, so if
+* the file was grayscale the background value is gray.
+*/
+if (!(png_ptr->color_type & PNG_COLOR_MASK_COLOR))
+png_ptr->mode |= PNG_BACKGROUND_IS_GRAY;
+}
+else if (png_ptr->transformations & PNG_COMPOSE)
+{
+/* PNG_COMPOSE: png_set_background was called with need_expand false,
+* so the color is in the color space of the output or png_set_alpha_mode
+* was called and the color is black.  Ignore RGB_TO_GRAY because that
+* happens before GRAY_TO_RGB.
+*/
+if (png_ptr->transformations & PNG_GRAY_TO_RGB)
+{
+if (png_ptr->background.red == png_ptr->background.green &&
+png_ptr->background.red == png_ptr->background.blue)
+{
+png_ptr->mode |= PNG_BACKGROUND_IS_GRAY;
+png_ptr->background.gray = png_ptr->background.red;
+}
+}
+}
+#endif /* PNG_READ_EXPAND_SUPPORTED && PNG_READ_BACKGROUND_SUPPORTED */
+#endif /* PNG_READ_GRAY_TO_RGB_SUPPORTED */
+/* For indexed PNG data (PNG_COLOR_TYPE_PALETTE) many of the transformations
+* can be performed directly on the palette, and some (such as rgb to gray)
+* can be optimized inside the palette.  This is particularly true of the
+* composite (background and alpha) stuff, which can be pretty much all done
+* in the palette even if the result is expanded to RGB or gray afterward.
+*
+* NOTE: this is Not Yet Implemented, the code behaves as in 1.5.1 and
+* earlier and the palette stuff is actually handled on the first row.  This
+* leads to the reported bug that the palette returned by png_get_PLTE is not
+* updated.
+*/
+if (png_ptr->color_type == PNG_COLOR_TYPE_PALETTE)
+png_init_palette_transformations(png_ptr);
+else
+png_init_rgb_transformations(png_ptr);
+#if defined(PNG_READ_BACKGROUND_SUPPORTED) && \
+defined(PNG_READ_EXPAND_16_SUPPORTED)
+if ((png_ptr->transformations & PNG_EXPAND_16) &&
+(png_ptr->transformations & PNG_COMPOSE) &&
+!(png_ptr->transformations & PNG_BACKGROUND_EXPAND) &&
+png_ptr->bit_depth != 16)
+{
+/* TODO: fix this.  Because the expand_16 operation is after the compose
+* handling the background color must be 8, not 16, bits deep, but the
+* application will supply a 16-bit value so reduce it here.
+*
+* The PNG_BACKGROUND_EXPAND code above does not expand to 16 bits at
+* present, so that case is ok (until do_expand_16 is moved.)
+*
+* NOTE: this discards the low 16 bits of the user supplied background
+* color, but until expand_16 works properly there is no choice!
+*/
+#     define CHOP(x) (x)=((png_uint_16)PNG_DIV257(x))
+CHOP(png_ptr->background.red);
+CHOP(png_ptr->background.green);
+CHOP(png_ptr->background.blue);
+CHOP(png_ptr->background.gray);
+#     undef CHOP
+}
+#endif /* PNG_READ_BACKGROUND_SUPPORTED && PNG_READ_EXPAND_16_SUPPORTED */
+#if defined(PNG_READ_BACKGROUND_SUPPORTED) && \
+(defined(PNG_READ_SCALE_16_TO_8_SUPPORTED) || \
+defined(PNG_READ_STRIP_16_TO_8_SUPPORTED))
+if ((png_ptr->transformations & (PNG_16_TO_8|PNG_SCALE_16_TO_8)) &&
+(png_ptr->transformations & PNG_COMPOSE) &&
+!(png_ptr->transformations & PNG_BACKGROUND_EXPAND) &&
+png_ptr->bit_depth == 16)
+{
+/* On the other hand, if a 16-bit file is to be reduced to 8-bits per
+* component this will also happen after PNG_COMPOSE and so the background
+* color must be pre-expanded here.
+*
+* TODO: fix this too.
+*/
+png_ptr->background.red = (png_uint_16)(png_ptr->background.red * 257);
+png_ptr->background.green =
+(png_uint_16)(png_ptr->background.green * 257);
+png_ptr->background.blue = (png_uint_16)(png_ptr->background.blue * 257);
+png_ptr->background.gray = (png_uint_16)(png_ptr->background.gray * 257);
+}
+#endif
+/* NOTE: below 'PNG_READ_ALPHA_MODE_SUPPORTED' is presumed to also enable the
+* background support (see the comments in scripts/pnglibconf.dfa), this
+* allows pre-multiplication of the alpha channel to be implemented as
+* compositing on black.  This is probably sub-optimal and has been done in
+* 1.5.4 betas simply to enable external critique and testing (i.e. to
+* implement the new API quickly, without lots of internal changes.)
+*/
+#ifdef PNG_READ_GAMMA_SUPPORTED
+#  ifdef PNG_READ_BACKGROUND_SUPPORTED
+/* Includes ALPHA_MODE */
+png_ptr->background_1 = png_ptr->background;
+#  endif
+/* This needs to change - in the palette image case a whole set of tables are
+* built when it would be quicker to just calculate the correct value for
+* each palette entry directly.  Also, the test is too tricky - why check
+* PNG_RGB_TO_GRAY if PNG_GAMMA is not set?  The answer seems to be that
+* PNG_GAMMA is cancelled even if the gamma is known?  The test excludes the
+* PNG_COMPOSE case, so apparently if there is no *overall* gamma correction
+* the gamma tables will not be built even if composition is required on a
+* gamma encoded value.
+*
+* In 1.5.4 this is addressed below by an additional check on the individual
+* file gamma - if it is not 1.0 both RGB_TO_GRAY and COMPOSE need the
+* tables.
+*/
+if ((png_ptr->transformations & PNG_GAMMA)
+|| ((png_ptr->transformations & PNG_RGB_TO_GRAY)
+&& (png_gamma_significant(png_ptr->colorspace.gamma) ||
+png_gamma_significant(png_ptr->screen_gamma)))
+|| ((png_ptr->transformations & PNG_COMPOSE)
+&& (png_gamma_significant(png_ptr->colorspace.gamma)
+|| png_gamma_significant(png_ptr->screen_gamma)
+#  ifdef PNG_READ_BACKGROUND_SUPPORTED
+|| (png_ptr->background_gamma_type == PNG_BACKGROUND_GAMMA_UNIQUE
+&& png_gamma_significant(png_ptr->background_gamma))
+#  endif
+)) || ((png_ptr->transformations & PNG_ENCODE_ALPHA)
+&& png_gamma_significant(png_ptr->screen_gamma))
+)
+{
+png_build_gamma_table(png_ptr, png_ptr->bit_depth);
+#ifdef PNG_READ_BACKGROUND_SUPPORTED
+if (png_ptr->transformations & PNG_COMPOSE)
+{
+/* Issue a warning about this combination: because RGB_TO_GRAY is
+* optimized to do the gamma transform if present yet do_background has
+* to do the same thing if both options are set a
+* double-gamma-correction happens.  This is true in all versions of
+* libpng to date.
+*/
+if (png_ptr->transformations & PNG_RGB_TO_GRAY)
+png_warning(png_ptr,
+"libpng does not support gamma+background+rgb_to_gray");
+if (png_ptr->color_type == PNG_COLOR_TYPE_PALETTE)
+{
+/* We don't get to here unless there is a tRNS chunk with non-opaque
+* entries - see the checking code at the start of this function.
+*/
+png_color back, back_1;
+png_colorp palette = png_ptr->palette;
+int num_palette = png_ptr->num_palette;
+int i;
+if (png_ptr->background_gamma_type == PNG_BACKGROUND_GAMMA_FILE)
+{
+back.red = png_ptr->gamma_table[png_ptr->background.red];
+back.green = png_ptr->gamma_table[png_ptr->background.green];
+back.blue = png_ptr->gamma_table[png_ptr->background.blue];
+back_1.red = png_ptr->gamma_to_1[png_ptr->background.red];
+back_1.green = png_ptr->gamma_to_1[png_ptr->background.green];
+back_1.blue = png_ptr->gamma_to_1[png_ptr->background.blue];
+}
+else
+{
+png_fixed_point g, gs;
+switch (png_ptr->background_gamma_type)
+{
+case PNG_BACKGROUND_GAMMA_SCREEN:
+g = (png_ptr->screen_gamma);
+gs = PNG_FP_1;
+break;
+case PNG_BACKGROUND_GAMMA_FILE:
+g = png_reciprocal(png_ptr->colorspace.gamma);
+gs = png_reciprocal2(png_ptr->colorspace.gamma,
+png_ptr->screen_gamma);
+break;
+case PNG_BACKGROUND_GAMMA_UNIQUE:
+g = png_reciprocal(png_ptr->background_gamma);
+gs = png_reciprocal2(png_ptr->background_gamma,
+png_ptr->screen_gamma);
+break;
+default:
+g = PNG_FP_1;    /* back_1 */
+gs = PNG_FP_1;   /* back */
+break;
+}
+if (png_gamma_significant(gs))
+{
+back.red = png_gamma_8bit_correct(png_ptr->background.red,
+gs);
+back.green = png_gamma_8bit_correct(png_ptr->background.green,
+gs);
+back.blue = png_gamma_8bit_correct(png_ptr->background.blue,
+gs);
+}
+else
+{
+back.red   = (png_byte)png_ptr->background.red;
+back.green = (png_byte)png_ptr->background.green;
+back.blue  = (png_byte)png_ptr->background.blue;
+}
+if (png_gamma_significant(g))
+{
+back_1.red = png_gamma_8bit_correct(png_ptr->background.red,
+g);
+back_1.green = png_gamma_8bit_correct(
+png_ptr->background.green, g);
+back_1.blue = png_gamma_8bit_correct(png_ptr->background.blue,
+g);
+}
+else
+{
+back_1.red   = (png_byte)png_ptr->background.red;
+back_1.green = (png_byte)png_ptr->background.green;
+back_1.blue  = (png_byte)png_ptr->background.blue;
+}
+}
+for (i = 0; i < num_palette; i++)
+{
+if (i < (int)png_ptr->num_trans &&
+png_ptr->trans_alpha[i] != 0xff)
+{
+if (png_ptr->trans_alpha[i] == 0)
+{
+palette[i] = back;
+}
+else /* if (png_ptr->trans_alpha[i] != 0xff) */
+{
+png_byte v, w;
+v = png_ptr->gamma_to_1[palette[i].red];
+png_composite(w, v, png_ptr->trans_alpha[i], back_1.red);
+palette[i].red = png_ptr->gamma_from_1[w];
+v = png_ptr->gamma_to_1[palette[i].green];
+png_composite(w, v, png_ptr->trans_alpha[i], back_1.green);
+palette[i].green = png_ptr->gamma_from_1[w];
+v = png_ptr->gamma_to_1[palette[i].blue];
+png_composite(w, v, png_ptr->trans_alpha[i], back_1.blue);
+palette[i].blue = png_ptr->gamma_from_1[w];
+}
+}
+else
+{
+palette[i].red = png_ptr->gamma_table[palette[i].red];
+palette[i].green = png_ptr->gamma_table[palette[i].green];
+palette[i].blue = png_ptr->gamma_table[palette[i].blue];
+}
+}
+/* Prevent the transformations being done again.
+*
+* NOTE: this is highly dubious; it removes the transformations in
+* place.  This seems inconsistent with the general treatment of the
+* transformations elsewhere.
+*/
+png_ptr->transformations &= ~(PNG_COMPOSE | PNG_GAMMA);
+} /* color_type == PNG_COLOR_TYPE_PALETTE */
+/* if (png_ptr->background_gamma_type!=PNG_BACKGROUND_GAMMA_UNKNOWN) */
+else /* color_type != PNG_COLOR_TYPE_PALETTE */
+{
+int gs_sig, g_sig;
+png_fixed_point g = PNG_FP_1;  /* Correction to linear */
+png_fixed_point gs = PNG_FP_1; /* Correction to screen */
+switch (png_ptr->background_gamma_type)
+{
+case PNG_BACKGROUND_GAMMA_SCREEN:
+g = png_ptr->screen_gamma;
+/* gs = PNG_FP_1; */
+break;
+case PNG_BACKGROUND_GAMMA_FILE:
+g = png_reciprocal(png_ptr->colorspace.gamma);
+gs = png_reciprocal2(png_ptr->colorspace.gamma,
+png_ptr->screen_gamma);
+break;
+case PNG_BACKGROUND_GAMMA_UNIQUE:
+g = png_reciprocal(png_ptr->background_gamma);
+gs = png_reciprocal2(png_ptr->background_gamma,
+png_ptr->screen_gamma);
+break;
+default:
+png_error(png_ptr, "invalid background gamma type");
+}
+g_sig = png_gamma_significant(g);
+gs_sig = png_gamma_significant(gs);
+if (g_sig)
+png_ptr->background_1.gray = png_gamma_correct(png_ptr,
+png_ptr->background.gray, g);
+if (gs_sig)
+png_ptr->background.gray = png_gamma_correct(png_ptr,
+png_ptr->background.gray, gs);
+if ((png_ptr->background.red != png_ptr->background.green) ||
+(png_ptr->background.red != png_ptr->background.blue) ||
+(png_ptr->background.red != png_ptr->background.gray))
+{
+/* RGB or RGBA with color background */
+if (g_sig)
+{
+png_ptr->background_1.red = png_gamma_correct(png_ptr,
+png_ptr->background.red, g);
+png_ptr->background_1.green = png_gamma_correct(png_ptr,
+png_ptr->background.green, g);
+png_ptr->background_1.blue = png_gamma_correct(png_ptr,
+png_ptr->background.blue, g);
+}
+if (gs_sig)
+{
+png_ptr->background.red = png_gamma_correct(png_ptr,
+png_ptr->background.red, gs);
+png_ptr->background.green = png_gamma_correct(png_ptr,
+png_ptr->background.green, gs);
+png_ptr->background.blue = png_gamma_correct(png_ptr,
+png_ptr->background.blue, gs);
+}
+}
+else
+{
+/* GRAY, GRAY ALPHA, RGB, or RGBA with gray background */
+png_ptr->background_1.red = png_ptr->background_1.green
+= png_ptr->background_1.blue = png_ptr->background_1.gray;
+png_ptr->background.red = png_ptr->background.green
+= png_ptr->background.blue = png_ptr->background.gray;
+}
+/* The background is now in screen gamma: */
+png_ptr->background_gamma_type = PNG_BACKGROUND_GAMMA_SCREEN;
+} /* color_type != PNG_COLOR_TYPE_PALETTE */
+}/* png_ptr->transformations & PNG_BACKGROUND */
+else
+/* Transformation does not include PNG_BACKGROUND */
+#endif /* PNG_READ_BACKGROUND_SUPPORTED */
+if (png_ptr->color_type == PNG_COLOR_TYPE_PALETTE
+#ifdef PNG_READ_RGB_TO_GRAY_SUPPORTED
+/* RGB_TO_GRAY needs to have non-gamma-corrected values! */
+&& ((png_ptr->transformations & PNG_EXPAND) == 0 ||
+(png_ptr->transformations & PNG_RGB_TO_GRAY) == 0)
+#endif
+)
+{
+png_colorp palette = png_ptr->palette;
+int num_palette = png_ptr->num_palette;
+int i;
+/* NOTE: there are other transformations that should probably be in
+* here too.
+*/
+for (i = 0; i < num_palette; i++)
+{
+palette[i].red = png_ptr->gamma_table[palette[i].red];
+palette[i].green = png_ptr->gamma_table[palette[i].green];
+palette[i].blue = png_ptr->gamma_table[palette[i].blue];
+}
+/* Done the gamma correction. */
+png_ptr->transformations &= ~PNG_GAMMA;
+} /* color_type == PALETTE && !PNG_BACKGROUND transformation */
+}
+#ifdef PNG_READ_BACKGROUND_SUPPORTED
+else
+#endif
+#endif /* PNG_READ_GAMMA_SUPPORTED */
+#ifdef PNG_READ_BACKGROUND_SUPPORTED
+/* No GAMMA transformation (see the hanging else 4 lines above) */
+if ((png_ptr->transformations & PNG_COMPOSE) &&
+(png_ptr->color_type == PNG_COLOR_TYPE_PALETTE))
+{
+int i;
+int istop = (int)png_ptr->num_trans;
+png_color back;
+png_colorp palette = png_ptr->palette;
+back.red   = (png_byte)png_ptr->background.red;
+back.green = (png_byte)png_ptr->background.green;
+back.blue  = (png_byte)png_ptr->background.blue;
+for (i = 0; i < istop; i++)
+{
+if (png_ptr->trans_alpha[i] == 0)
+{
+palette[i] = back;
+}
+else if (png_ptr->trans_alpha[i] != 0xff)
+{
+/* The png_composite() macro is defined in png.h */
+png_composite(palette[i].red, palette[i].red,
+png_ptr->trans_alpha[i], back.red);
+png_composite(palette[i].green, palette[i].green,
+png_ptr->trans_alpha[i], back.green);
+png_composite(palette[i].blue, palette[i].blue,
+png_ptr->trans_alpha[i], back.blue);
+}
+}
+png_ptr->transformations &= ~PNG_COMPOSE;
+}
+#endif /* PNG_READ_BACKGROUND_SUPPORTED */
+#ifdef PNG_READ_SHIFT_SUPPORTED
+if ((png_ptr->transformations & PNG_SHIFT) &&
+!(png_ptr->transformations & PNG_EXPAND) &&
+(png_ptr->color_type == PNG_COLOR_TYPE_PALETTE))
+{
+int i;
+int istop = png_ptr->num_palette;
+int shift = 8 - png_ptr->sig_bit.red;
+png_ptr->transformations &= ~PNG_SHIFT;
+/* significant bits can be in the range 1 to 7 for a meaninful result, if
+* the number of significant bits is 0 then no shift is done (this is an
+* error condition which is silently ignored.)
+*/
+if (shift > 0 && shift < 8)
+for (i=0; i<istop; ++i)
+{
+int component = png_ptr->palette[i].red;
+component >>= shift;
+png_ptr->palette[i].red = (png_byte)component;
+}
+shift = 8 - png_ptr->sig_bit.green;
+if (shift > 0 && shift < 8)
+for (i=0; i<istop; ++i)
+{
+int component = png_ptr->palette[i].green;
+component >>= shift;
+png_ptr->palette[i].green = (png_byte)component;
+}
+shift = 8 - png_ptr->sig_bit.blue;
+if (shift > 0 && shift < 8)
+for (i=0; i<istop; ++i)
+{
+int component = png_ptr->palette[i].blue;
+component >>= shift;
+png_ptr->palette[i].blue = (png_byte)component;
+}
+}
+#endif  /* PNG_READ_SHIFT_SUPPORTED */
+}
+/* Modify the info structure to reflect the transformations.  The
+* info should be updated so a PNG file could be written with it,
+* assuming the transformations result in valid PNG data.
+*/
+void /* PRIVATE */
+png_read_transform_info(png_structrp png_ptr, png_inforp info_ptr)
+{
+png_debug(1, "in png_read_transform_info");
+#ifdef PNG_READ_EXPAND_SUPPORTED
+if (png_ptr->transformations & PNG_EXPAND)
+{
+if (info_ptr->color_type == PNG_COLOR_TYPE_PALETTE)
+{
+/* This check must match what actually happens in
+* png_do_expand_palette; if it ever checks the tRNS chunk to see if
+* it is all opaque we must do the same (at present it does not.)
+*/
+if (png_ptr->num_trans > 0)
+info_ptr->color_type = PNG_COLOR_TYPE_RGB_ALPHA;
+else
+info_ptr->color_type = PNG_COLOR_TYPE_RGB;
+info_ptr->bit_depth = 8;
+info_ptr->num_trans = 0;
+if (png_ptr->palette == NULL)
+png_error (png_ptr, "Palette is NULL in indexed image");
+}
+else
+{
+if (png_ptr->num_trans)
+{
+if (png_ptr->transformations & PNG_EXPAND_tRNS)
+info_ptr->color_type |= PNG_COLOR_MASK_ALPHA;
+}
+if (info_ptr->bit_depth < 8)
+info_ptr->bit_depth = 8;
+info_ptr->num_trans = 0;
+}
+}
+#endif
+#if defined(PNG_READ_BACKGROUND_SUPPORTED) ||\
+defined(PNG_READ_ALPHA_MODE_SUPPORTED)
+/* The following is almost certainly wrong unless the background value is in
+* the screen space!
+*/
+if (png_ptr->transformations & PNG_COMPOSE)
+info_ptr->background = png_ptr->background;
+#endif
+#ifdef PNG_READ_GAMMA_SUPPORTED
+/* The following used to be conditional on PNG_GAMMA (prior to 1.5.4),
+* however it seems that the code in png_init_read_transformations, which has
+* been called before this from png_read_update_info->png_read_start_row
+* sometimes does the gamma transform and cancels the flag.
+*
+* TODO: this looks wrong; the info_ptr should end up with a gamma equal to
+* the screen_gamma value.  The following probably results in weirdness if
+* the info_ptr is used by the app after the rows have been read.
+*/
+info_ptr->colorspace.gamma = png_ptr->colorspace.gamma;
+#endif
+if (info_ptr->bit_depth == 16)
+{
+#  ifdef PNG_READ_16BIT_SUPPORTED
+#     ifdef PNG_READ_SCALE_16_TO_8_SUPPORTED
+if (png_ptr->transformations & PNG_SCALE_16_TO_8)
+info_ptr->bit_depth = 8;
+#     endif
+#     ifdef PNG_READ_STRIP_16_TO_8_SUPPORTED
+if (png_ptr->transformations & PNG_16_TO_8)
+info_ptr->bit_depth = 8;
+#     endif
+#  else
+/* No 16 bit support: force chopping 16-bit input down to 8, in this case
+* the app program can chose if both APIs are available by setting the
+* correct scaling to use.
+*/
+#     ifdef PNG_READ_STRIP_16_TO_8_SUPPORTED
+/* For compatibility with previous versions use the strip method by
+* default.  This code works because if PNG_SCALE_16_TO_8 is already
+* set the code below will do that in preference to the chop.
+*/
+png_ptr->transformations |= PNG_16_TO_8;
+info_ptr->bit_depth = 8;
+#     else
+#        ifdef PNG_READ_SCALE_16_TO_8_SUPPORTED
+png_ptr->transformations |= PNG_SCALE_16_TO_8;
+info_ptr->bit_depth = 8;
+#        else
+CONFIGURATION ERROR: you must enable at least one 16 to 8 method
+#        endif
+#    endif
+#endif /* !READ_16BIT_SUPPORTED */
+}
+#ifdef PNG_READ_GRAY_TO_RGB_SUPPORTED
+if (png_ptr->transformations & PNG_GRAY_TO_RGB)
+info_ptr->color_type = (png_byte)(info_ptr->color_type |
+PNG_COLOR_MASK_COLOR);
+#endif
+#ifdef PNG_READ_RGB_TO_GRAY_SUPPORTED
+if (png_ptr->transformations & PNG_RGB_TO_GRAY)
+info_ptr->color_type = (png_byte)(info_ptr->color_type &
+~PNG_COLOR_MASK_COLOR);
+#endif
+#ifdef PNG_READ_QUANTIZE_SUPPORTED
+if (png_ptr->transformations & PNG_QUANTIZE)
+{
+if (((info_ptr->color_type == PNG_COLOR_TYPE_RGB) ||
+(info_ptr->color_type == PNG_COLOR_TYPE_RGB_ALPHA)) &&
+png_ptr->palette_lookup && info_ptr->bit_depth == 8)
+{
+info_ptr->color_type = PNG_COLOR_TYPE_PALETTE;
+}
+}
+#endif
+#ifdef PNG_READ_EXPAND_16_SUPPORTED
+if (png_ptr->transformations & PNG_EXPAND_16 && info_ptr->bit_depth == 8 &&
+info_ptr->color_type != PNG_COLOR_TYPE_PALETTE)
+{
+info_ptr->bit_depth = 16;
+}
+#endif
+#ifdef PNG_READ_PACK_SUPPORTED
+if ((png_ptr->transformations & PNG_PACK) && (info_ptr->bit_depth < 8))
+info_ptr->bit_depth = 8;
+#endif
+if (info_ptr->color_type == PNG_COLOR_TYPE_PALETTE)
+info_ptr->channels = 1;
+else if (info_ptr->color_type & PNG_COLOR_MASK_COLOR)
+info_ptr->channels = 3;
+else
+info_ptr->channels = 1;
+#ifdef PNG_READ_STRIP_ALPHA_SUPPORTED
+if (png_ptr->transformations & PNG_STRIP_ALPHA)
+{
+info_ptr->color_type = (png_byte)(info_ptr->color_type &
+~PNG_COLOR_MASK_ALPHA);
+info_ptr->num_trans = 0;
+}
+#endif
+if (info_ptr->color_type & PNG_COLOR_MASK_ALPHA)
+info_ptr->channels++;
+#ifdef PNG_READ_FILLER_SUPPORTED
+/* STRIP_ALPHA and FILLER allowed:  MASK_ALPHA bit stripped above */
+if ((png_ptr->transformations & PNG_FILLER) &&
+((info_ptr->color_type == PNG_COLOR_TYPE_RGB) ||
+(info_ptr->color_type == PNG_COLOR_TYPE_GRAY)))
+{
+info_ptr->channels++;
+/* If adding a true alpha channel not just filler */
+if (png_ptr->transformations & PNG_ADD_ALPHA)
+info_ptr->color_type |= PNG_COLOR_MASK_ALPHA;
+}
+#endif
+#if defined(PNG_USER_TRANSFORM_PTR_SUPPORTED) && \
+defined(PNG_READ_USER_TRANSFORM_SUPPORTED)
+if (png_ptr->transformations & PNG_USER_TRANSFORM)
+{
+if (info_ptr->bit_depth < png_ptr->user_transform_depth)
+info_ptr->bit_depth = png_ptr->user_transform_depth;
+if (info_ptr->channels < png_ptr->user_transform_channels)
+info_ptr->channels = png_ptr->user_transform_channels;
+}
+#endif
+info_ptr->pixel_depth = (png_byte)(info_ptr->channels *
+info_ptr->bit_depth);
+info_ptr->rowbytes = PNG_ROWBYTES(info_ptr->pixel_depth, info_ptr->width);
+/* Adding in 1.5.4: cache the above value in png_struct so that we can later
+* check in png_rowbytes that the user buffer won't get overwritten.  Note
+* that the field is not always set - if png_read_update_info isn't called
+* the application has to either not do any transforms or get the calculation
+* right itself.
+*/
+png_ptr->info_rowbytes = info_ptr->rowbytes;
+#ifndef PNG_READ_EXPAND_SUPPORTED
+if (png_ptr)
+return;
+#endif
+}
+#ifdef PNG_READ_PACK_SUPPORTED
+/* Unpack pixels of 1, 2, or 4 bits per pixel into 1 byte per pixel,
+* without changing the actual values.  Thus, if you had a row with
+* a bit depth of 1, you would end up with bytes that only contained
+* the numbers 0 or 1.  If you would rather they contain 0 and 255, use
+* png_do_shift() after this.
+*/
+static void
+png_do_unpack(png_row_infop row_info, png_bytep row)
+{
+png_debug(1, "in png_do_unpack");
+if (row_info->bit_depth < 8)
+{
+png_uint_32 i;
+png_uint_32 row_width=row_info->width;
+switch (row_info->bit_depth)
+{
+case 1:
+{
+png_bytep sp = row + (png_size_t)((row_width - 1) >> 3);
+png_bytep dp = row + (png_size_t)row_width - 1;
+png_uint_32 shift = 7 - (int)((row_width + 7) & 0x07);
+for (i = 0; i < row_width; i++)
+{
+*dp = (png_byte)((*sp >> shift) & 0x01);
+if (shift == 7)
+{
+shift = 0;
+sp--;
+}
+else
+shift++;
+dp--;
+}
+break;
+}
+case 2:
+{
+png_bytep sp = row + (png_size_t)((row_width - 1) >> 2);
+png_bytep dp = row + (png_size_t)row_width - 1;
+png_uint_32 shift = (int)((3 - ((row_width + 3) & 0x03)) << 1);
+for (i = 0; i < row_width; i++)
+{
+*dp = (png_byte)((*sp >> shift) & 0x03);
+if (shift == 6)
+{
+shift = 0;
+sp--;
+}
+else
+shift += 2;
+dp--;
+}
+break;
+}
+case 4:
+{
+png_bytep sp = row + (png_size_t)((row_width - 1) >> 1);
+png_bytep dp = row + (png_size_t)row_width - 1;
+png_uint_32 shift = (int)((1 - ((row_width + 1) & 0x01)) << 2);
+for (i = 0; i < row_width; i++)
+{
+*dp = (png_byte)((*sp >> shift) & 0x0f);
+if (shift == 4)
+{
+shift = 0;
+sp--;
+}
+else
+shift = 4;
+dp--;
+}
+break;
+}
+default:
+break;
+}
+row_info->bit_depth = 8;
+row_info->pixel_depth = (png_byte)(8 * row_info->channels);
+row_info->rowbytes = row_width * row_info->channels;
+}
+}
+#endif
+#ifdef PNG_READ_SHIFT_SUPPORTED
+/* Reverse the effects of png_do_shift.  This routine merely shifts the
+* pixels back to their significant bits values.  Thus, if you have
+* a row of bit depth 8, but only 5 are significant, this will shift
+* the values back to 0 through 31.
+*/
+static void
+png_do_unshift(png_row_infop row_info, png_bytep row,
+png_const_color_8p sig_bits)
+{
+int color_type;
+png_debug(1, "in png_do_unshift");
+/* The palette case has already been handled in the _init routine. */
+color_type = row_info->color_type;
+if (color_type != PNG_COLOR_TYPE_PALETTE)
+{
+int shift[4];
+int channels = 0;
+int bit_depth = row_info->bit_depth;
+if (color_type & PNG_COLOR_MASK_COLOR)
+{
+shift[channels++] = bit_depth - sig_bits->red;
+shift[channels++] = bit_depth - sig_bits->green;
+shift[channels++] = bit_depth - sig_bits->blue;
+}
+else
+{
+shift[channels++] = bit_depth - sig_bits->gray;
+}
+if (color_type & PNG_COLOR_MASK_ALPHA)
+{
+shift[channels++] = bit_depth - sig_bits->alpha;
+}
+{
+int c, have_shift;
+for (c = have_shift = 0; c < channels; ++c)
+{
+/* A shift of more than the bit depth is an error condition but it
+* gets ignored here.
+*/
+if (shift[c] <= 0 || shift[c] >= bit_depth)
+shift[c] = 0;
+else
+have_shift = 1;
+}
+if (!have_shift)
+return;
+}
+switch (bit_depth)
+{
+default:
+/* Must be 1bpp gray: should not be here! */
+/* NOTREACHED */
+break;
+case 2:
+/* Must be 2bpp gray */
+/* assert(channels == 1 && shift[0] == 1) */
+{
+png_bytep bp = row;
+png_bytep bp_end = bp + row_info->rowbytes;
+while (bp < bp_end)
+{
+int b = (*bp >> 1) & 0x55;
+*bp++ = (png_byte)b;
+}
+break;
+}
+case 4:
+/* Must be 4bpp gray */
+/* assert(channels == 1) */
+{
+png_bytep bp = row;
+png_bytep bp_end = bp + row_info->rowbytes;
+int gray_shift = shift[0];
+int mask =  0xf >> gray_shift;
+mask |= mask << 4;
+while (bp < bp_end)
+{
+int b = (*bp >> gray_shift) & mask;
+*bp++ = (png_byte)b;
+}
+break;
+}
+case 8:
+/* Single byte components, G, GA, RGB, RGBA */
+{
+png_bytep bp = row;
+png_bytep bp_end = bp + row_info->rowbytes;
+int channel = 0;
+while (bp < bp_end)
+{
+int b = *bp >> shift[channel];
+if (++channel >= channels)
+channel = 0;
+*bp++ = (png_byte)b;
+}
+break;
+}
+#ifdef PNG_READ_16BIT_SUPPORTED
+case 16:
+/* Double byte components, G, GA, RGB, RGBA */
+{
+png_bytep bp = row;
+png_bytep bp_end = bp + row_info->rowbytes;
+int channel = 0;
+while (bp < bp_end)
+{
+int value = (bp[0] << 8) + bp[1];
+value >>= shift[channel];
+if (++channel >= channels)
+channel = 0;
+*bp++ = (png_byte)(value >> 8);
+*bp++ = (png_byte)(value & 0xff);
+}
+break;
+}
+#endif
+}
+}
+}
+#endif
+#ifdef PNG_READ_SCALE_16_TO_8_SUPPORTED
+/* Scale rows of bit depth 16 down to 8 accurately */
+static void
+png_do_scale_16_to_8(png_row_infop row_info, png_bytep row)
+{
+png_debug(1, "in png_do_scale_16_to_8");
+if (row_info->bit_depth == 16)
+{
+png_bytep sp = row; /* source */
+png_bytep dp = row; /* destination */
+png_bytep ep = sp + row_info->rowbytes; /* end+1 */
+while (sp < ep)
+{
+/* The input is an array of 16 bit components, these must be scaled to
+* 8 bits each.  For a 16 bit value V the required value (from the PNG
+* specification) is:
+*
+*    (V * 255) / 65535
+*
+* This reduces to round(V / 257), or floor((V + 128.5)/257)
+*
+* Represent V as the two byte value vhi.vlo.  Make a guess that the
+* result is the top byte of V, vhi, then the correction to this value
+* is:
+*
+*    error = floor(((V-vhi.vhi) + 128.5) / 257)
+*          = floor(((vlo-vhi) + 128.5) / 257)
+*
+* This can be approximated using integer arithmetic (and a signed
+* shift):
+*
+*    error = (vlo-vhi+128) >> 8;
+*
+* The approximate differs from the exact answer only when (vlo-vhi) is
+* 128; it then gives a correction of +1 when the exact correction is
+* 0.  This gives 128 errors.  The exact answer (correct for all 16 bit
+* input values) is:
+*
+*    error = (vlo-vhi+128)*65535 >> 24;
+*
+* An alternative arithmetic calculation which also gives no errors is:
+*
+*    (V * 255 + 32895) >> 16
+*/
+png_int_32 tmp = *sp++; /* must be signed! */
+tmp += (((int)*sp++ - tmp + 128) * 65535) >> 24;
+*dp++ = (png_byte)tmp;
+}
+row_info->bit_depth = 8;
+row_info->pixel_depth = (png_byte)(8 * row_info->channels);
+row_info->rowbytes = row_info->width * row_info->channels;
+}
+}
+#endif
+#ifdef PNG_READ_STRIP_16_TO_8_SUPPORTED
+static void
+/* Simply discard the low byte.  This was the default behavior prior
+* to libpng-1.5.4.
+*/
+png_do_chop(png_row_infop row_info, png_bytep row)
+{
+png_debug(1, "in png_do_chop");
+if (row_info->bit_depth == 16)
+{
+png_bytep sp = row; /* source */
+png_bytep dp = row; /* destination */
+png_bytep ep = sp + row_info->rowbytes; /* end+1 */
+while (sp < ep)
+{
+*dp++ = *sp;
+sp += 2; /* skip low byte */
+}
+row_info->bit_depth = 8;
+row_info->pixel_depth = (png_byte)(8 * row_info->channels);
+row_info->rowbytes = row_info->width * row_info->channels;
+}
+}
+#endif
+#ifdef PNG_READ_SWAP_ALPHA_SUPPORTED
+static void
+png_do_read_swap_alpha(png_row_infop row_info, png_bytep row)
+{
+png_debug(1, "in png_do_read_swap_alpha");
+{
+png_uint_32 row_width = row_info->width;
+if (row_info->color_type == PNG_COLOR_TYPE_RGB_ALPHA)
+{
+/* This converts from RGBA to ARGB */
+if (row_info->bit_depth == 8)
+{
+png_bytep sp = row + row_info->rowbytes;
+png_bytep dp = sp;
+png_byte save;
+png_uint_32 i;
+for (i = 0; i < row_width; i++)
+{
+save = *(--sp);
+*(--dp) = *(--sp);
+*(--dp) = *(--sp);
+*(--dp) = *(--sp);
+*(--dp) = save;
+}
+}
+#ifdef PNG_READ_16BIT_SUPPORTED
+/* This converts from RRGGBBAA to AARRGGBB */
+else
+{
+png_bytep sp = row + row_info->rowbytes;
+png_bytep dp = sp;
+png_byte save[2];
+png_uint_32 i;
+for (i = 0; i < row_width; i++)
+{
+save[0] = *(--sp);
+save[1] = *(--sp);
+*(--dp) = *(--sp);
+*(--dp) = *(--sp);
+*(--dp) = *(--sp);
+*(--dp) = *(--sp);
+*(--dp) = *(--sp);
+*(--dp) = *(--sp);
+*(--dp) = save[0];
+*(--dp) = save[1];
+}
+}
+#endif
+}
+else if (row_info->color_type == PNG_COLOR_TYPE_GRAY_ALPHA)
+{
+/* This converts from GA to AG */
+if (row_info->bit_depth == 8)
+{
+png_bytep sp = row + row_info->rowbytes;
+png_bytep dp = sp;
+png_byte save;
+png_uint_32 i;
+for (i = 0; i < row_width; i++)
+{
+save = *(--sp);
+*(--dp) = *(--sp);
+*(--dp) = save;
+}
+}
+#ifdef PNG_READ_16BIT_SUPPORTED
+/* This converts from GGAA to AAGG */
+else
+{
+png_bytep sp = row + row_info->rowbytes;
+png_bytep dp = sp;
+png_byte save[2];
+png_uint_32 i;
+for (i = 0; i < row_width; i++)
+{
+save[0] = *(--sp);
+save[1] = *(--sp);
+*(--dp) = *(--sp);
+*(--dp) = *(--sp);
+*(--dp) = save[0];
+*(--dp) = save[1];
+}
+}
+#endif
+}
+}
+}
+#endif
+#ifdef PNG_READ_INVERT_ALPHA_SUPPORTED
+static void
+png_do_read_invert_alpha(png_row_infop row_info, png_bytep row)
+{
+png_uint_32 row_width;
+png_debug(1, "in png_do_read_invert_alpha");
+row_width = row_info->width;
+if (row_info->color_type == PNG_COLOR_TYPE_RGB_ALPHA)
+{
+if (row_info->bit_depth == 8)
+{
+/* This inverts the alpha channel in RGBA */
+png_bytep sp = row + row_info->rowbytes;
+png_bytep dp = sp;
+png_uint_32 i;
+for (i = 0; i < row_width; i++)
+{
+*(--dp) = (png_byte)(255 - *(--sp));
+/*          This does nothing:
+*(--dp) = *(--sp);
+*(--dp) = *(--sp);
+*(--dp) = *(--sp);
+We can replace it with:
+*/
+sp-=3;
+dp=sp;
+}
+}
+#ifdef PNG_READ_16BIT_SUPPORTED
+/* This inverts the alpha channel in RRGGBBAA */
+else
+{
+png_bytep sp = row + row_info->rowbytes;
+png_bytep dp = sp;
+png_uint_32 i;
+for (i = 0; i < row_width; i++)
+{
+*(--dp) = (png_byte)(255 - *(--sp));
+*(--dp) = (png_byte)(255 - *(--sp));
+/*          This does nothing:
+*(--dp) = *(--sp);
+*(--dp) = *(--sp);
+*(--dp) = *(--sp);
+*(--dp) = *(--sp);
+*(--dp) = *(--sp);
+*(--dp) = *(--sp);
+We can replace it with:
+*/
+sp-=6;
+dp=sp;
+}
+}
+#endif
+}
+else if (row_info->color_type == PNG_COLOR_TYPE_GRAY_ALPHA)
+{
+if (row_info->bit_depth == 8)
+{
+/* This inverts the alpha channel in GA */
+png_bytep sp = row + row_info->rowbytes;
+png_bytep dp = sp;
+png_uint_32 i;
+for (i = 0; i < row_width; i++)
+{
+*(--dp) = (png_byte)(255 - *(--sp));
+*(--dp) = *(--sp);
+}
+}
+#ifdef PNG_READ_16BIT_SUPPORTED
+else
+{
+/* This inverts the alpha channel in GGAA */
+png_bytep sp  = row + row_info->rowbytes;
+png_bytep dp = sp;
+png_uint_32 i;
+for (i = 0; i < row_width; i++)
+{
+*(--dp) = (png_byte)(255 - *(--sp));
+*(--dp) = (png_byte)(255 - *(--sp));
+/*
+*(--dp) = *(--sp);
+*(--dp) = *(--sp);
+*/
+sp-=2;
+dp=sp;
+}
+}
+#endif
+}
+}
+#endif
+#ifdef PNG_READ_FILLER_SUPPORTED
+/* Add filler channel if we have RGB color */
+static void
+png_do_read_filler(png_row_infop row_info, png_bytep row,
+png_uint_32 filler, png_uint_32 flags)
+{
+png_uint_32 i;
+png_uint_32 row_width = row_info->width;
+#ifdef PNG_READ_16BIT_SUPPORTED
+png_byte hi_filler = (png_byte)((filler>>8) & 0xff);
+#endif
+png_byte lo_filler = (png_byte)(filler & 0xff);
+png_debug(1, "in png_do_read_filler");
+if (
+row_info->color_type == PNG_COLOR_TYPE_GRAY)
+{
+if (row_info->bit_depth == 8)
+{
+if (flags & PNG_FLAG_FILLER_AFTER)
+{
+/* This changes the data from G to GX */
+png_bytep sp = row + (png_size_t)row_width;
+png_bytep dp =  sp + (png_size_t)row_width;
+for (i = 1; i < row_width; i++)
+{
+*(--dp) = lo_filler;
+*(--dp) = *(--sp);
+}
+*(--dp) = lo_filler;
+row_info->channels = 2;
+row_info->pixel_depth = 16;
+row_info->rowbytes = row_width * 2;
+}
+else
+{
+/* This changes the data from G to XG */
+png_bytep sp = row + (png_size_t)row_width;
+png_bytep dp = sp  + (png_size_t)row_width;
+for (i = 0; i < row_width; i++)
+{
+*(--dp) = *(--sp);
+*(--dp) = lo_filler;
+}
+row_info->channels = 2;
+row_info->pixel_depth = 16;
+row_info->rowbytes = row_width * 2;
+}
+}
+#ifdef PNG_READ_16BIT_SUPPORTED
+else if (row_info->bit_depth == 16)
+{
+if (flags & PNG_FLAG_FILLER_AFTER)
+{
+/* This changes the data from GG to GGXX */
+png_bytep sp = row + (png_size_t)row_width * 2;
+png_bytep dp = sp  + (png_size_t)row_width * 2;
+for (i = 1; i < row_width; i++)
+{
+*(--dp) = hi_filler;
+*(--dp) = lo_filler;
+*(--dp) = *(--sp);
+*(--dp) = *(--sp);
+}
+*(--dp) = hi_filler;
+*(--dp) = lo_filler;
+row_info->channels = 2;
+row_info->pixel_depth = 32;
+row_info->rowbytes = row_width * 4;
+}
+else
+{
+/* This changes the data from GG to XXGG */
+png_bytep sp = row + (png_size_t)row_width * 2;
+png_bytep dp = sp  + (png_size_t)row_width * 2;
+for (i = 0; i < row_width; i++)
+{
+*(--dp) = *(--sp);
+*(--dp) = *(--sp);
+*(--dp) = hi_filler;
+*(--dp) = lo_filler;
+}
+row_info->channels = 2;
+row_info->pixel_depth = 32;
+row_info->rowbytes = row_width * 4;
+}
+}
+#endif
+} /* COLOR_TYPE == GRAY */
+else if (row_info->color_type == PNG_COLOR_TYPE_RGB)
+{
+if (row_info->bit_depth == 8)
+{
+if (flags & PNG_FLAG_FILLER_AFTER)
+{
+/* This changes the data from RGB to RGBX */
+png_bytep sp = row + (png_size_t)row_width * 3;
+png_bytep dp = sp  + (png_size_t)row_width;
+for (i = 1; i < row_width; i++)
+{
+*(--dp) = lo_filler;
+*(--dp) = *(--sp);
+*(--dp) = *(--sp);
+*(--dp) = *(--sp);
+}
+*(--dp) = lo_filler;
+row_info->channels = 4;
+row_info->pixel_depth = 32;
+row_info->rowbytes = row_width * 4;
+}
+else
+{
+/* This changes the data from RGB to XRGB */
+png_bytep sp = row + (png_size_t)row_width * 3;
+png_bytep dp = sp + (png_size_t)row_width;
+for (i = 0; i < row_width; i++)
+{
+*(--dp) = *(--sp);
+*(--dp) = *(--sp);
+*(--dp) = *(--sp);
+*(--dp) = lo_filler;
+}
+row_info->channels = 4;
+row_info->pixel_depth = 32;
+row_info->rowbytes = row_width * 4;
+}
+}
+#ifdef PNG_READ_16BIT_SUPPORTED
+else if (row_info->bit_depth == 16)
+{
+if (flags & PNG_FLAG_FILLER_AFTER)
+{
+/* This changes the data from RRGGBB to RRGGBBXX */
+png_bytep sp = row + (png_size_t)row_width * 6;
+png_bytep dp = sp  + (png_size_t)row_width * 2;
+for (i = 1; i < row_width; i++)
+{
+*(--dp) = hi_filler;
+*(--dp) = lo_filler;
+*(--dp) = *(--sp);
+*(--dp) = *(--sp);
+*(--dp) = *(--sp);
+*(--dp) = *(--sp);
+*(--dp) = *(--sp);
+*(--dp) = *(--sp);
+}
+*(--dp) = hi_filler;
+*(--dp) = lo_filler;
+row_info->channels = 4;
+row_info->pixel_depth = 64;
+row_info->rowbytes = row_width * 8;
+}
+else
+{
+/* This changes the data from RRGGBB to XXRRGGBB */
+png_bytep sp = row + (png_size_t)row_width * 6;
+png_bytep dp = sp  + (png_size_t)row_width * 2;
+for (i = 0; i < row_width; i++)
+{
+*(--dp) = *(--sp);
+*(--dp) = *(--sp);
+*(--dp) = *(--sp);
+*(--dp) = *(--sp);
+*(--dp) = *(--sp);
+*(--dp) = *(--sp);
+*(--dp) = hi_filler;
+*(--dp) = lo_filler;
+}
+row_info->channels = 4;
+row_info->pixel_depth = 64;
+row_info->rowbytes = row_width * 8;
+}
+}
+#endif
+} /* COLOR_TYPE == RGB */
+}
+#endif
+#ifdef PNG_READ_GRAY_TO_RGB_SUPPORTED
+/* Expand grayscale files to RGB, with or without alpha */
+static void
+png_do_gray_to_rgb(png_row_infop row_info, png_bytep row)
+{
+png_uint_32 i;
+png_uint_32 row_width = row_info->width;
+png_debug(1, "in png_do_gray_to_rgb");
+if (row_info->bit_depth >= 8 &&
+!(row_info->color_type & PNG_COLOR_MASK_COLOR))
+{
+if (row_info->color_type == PNG_COLOR_TYPE_GRAY)
+{
+if (row_info->bit_depth == 8)
+{
+/* This changes G to RGB */
+png_bytep sp = row + (png_size_t)row_width - 1;
+png_bytep dp = sp  + (png_size_t)row_width * 2;
+for (i = 0; i < row_width; i++)
+{
+*(dp--) = *sp;
+*(dp--) = *sp;
+*(dp--) = *(sp--);
+}
+}
+else
+{
+/* This changes GG to RRGGBB */
+png_bytep sp = row + (png_size_t)row_width * 2 - 1;
+png_bytep dp = sp  + (png_size_t)row_width * 4;
+for (i = 0; i < row_width; i++)
+{
+*(dp--) = *sp;
+*(dp--) = *(sp - 1);
+*(dp--) = *sp;
+*(dp--) = *(sp - 1);
+*(dp--) = *(sp--);
+*(dp--) = *(sp--);
+}
+}
+}
+else if (row_info->color_type == PNG_COLOR_TYPE_GRAY_ALPHA)
+{
+if (row_info->bit_depth == 8)
+{
+/* This changes GA to RGBA */
+png_bytep sp = row + (png_size_t)row_width * 2 - 1;
+png_bytep dp = sp  + (png_size_t)row_width * 2;
+for (i = 0; i < row_width; i++)
+{
+*(dp--) = *(sp--);
+*(dp--) = *sp;
+*(dp--) = *sp;
+*(dp--) = *(sp--);
+}
+}
+else
+{
+/* This changes GGAA to RRGGBBAA */
+png_bytep sp = row + (png_size_t)row_width * 4 - 1;
+png_bytep dp = sp  + (png_size_t)row_width * 4;
+for (i = 0; i < row_width; i++)
+{
+*(dp--) = *(sp--);
+*(dp--) = *(sp--);
+*(dp--) = *sp;
+*(dp--) = *(sp - 1);
+*(dp--) = *sp;
+*(dp--) = *(sp - 1);
+*(dp--) = *(sp--);
+*(dp--) = *(sp--);
+}
+}
+}
+row_info->channels = (png_byte)(row_info->channels + 2);
+row_info->color_type |= PNG_COLOR_MASK_COLOR;
+row_info->pixel_depth = (png_byte)(row_info->channels *
+row_info->bit_depth);
+row_info->rowbytes = PNG_ROWBYTES(row_info->pixel_depth, row_width);
+}
+}
+#endif
+#ifdef PNG_READ_RGB_TO_GRAY_SUPPORTED
+/* Reduce RGB files to grayscale, with or without alpha
+* using the equation given in Poynton's ColorFAQ of 1998-01-04 at
+* <http://www.inforamp.net/~poynton/>  (THIS LINK IS DEAD June 2008 but
+* versions dated 1998 through November 2002 have been archived at
+* http://web.archive.org/web/20000816232553/http://www.inforamp.net/
+* ~poynton/notes/colour_and_gamma/ColorFAQ.txt )
+* Charles Poynton poynton at poynton.com
+*
+*     Y = 0.212671 * R + 0.715160 * G + 0.072169 * B
+*
+*  which can be expressed with integers as
+*
+*     Y = (6969 * R + 23434 * G + 2365 * B)/32768
+*
+* Poynton's current link (as of January 2003 through July 2011):
+* <http://www.poynton.com/notes/colour_and_gamma/>
+* has changed the numbers slightly:
+*
+*     Y = 0.2126*R + 0.7152*G + 0.0722*B
+*
+*  which can be expressed with integers as
+*
+*     Y = (6966 * R + 23436 * G + 2366 * B)/32768
+*
+*  Historically, however, libpng uses numbers derived from the ITU-R Rec 709
+*  end point chromaticities and the D65 white point.  Depending on the
+*  precision used for the D65 white point this produces a variety of different
+*  numbers, however if the four decimal place value used in ITU-R Rec 709 is
+*  used (0.3127,0.3290) the Y calculation would be:
+*
+*     Y = (6968 * R + 23435 * G + 2366 * B)/32768
+*
+*  While this is correct the rounding results in an overflow for white, because
+*  the sum of the rounded coefficients is 32769, not 32768.  Consequently
+*  libpng uses, instead, the closest non-overflowing approximation:
+*
+*     Y = (6968 * R + 23434 * G + 2366 * B)/32768
+*
+*  Starting with libpng-1.5.5, if the image being converted has a cHRM chunk
+*  (including an sRGB chunk) then the chromaticities are used to calculate the
+*  coefficients.  See the chunk handling in pngrutil.c for more information.
+*
+*  In all cases the calculation is to be done in a linear colorspace.  If no
+*  gamma information is available to correct the encoding of the original RGB
+*  values this results in an implicit assumption that the original PNG RGB
+*  values were linear.
+*
+*  Other integer coefficents can be used via png_set_rgb_to_gray().  Because
+*  the API takes just red and green coefficients the blue coefficient is
+*  calculated to make the sum 32768.  This will result in different rounding
+*  to that used above.
+*/
+static int
+png_do_rgb_to_gray(png_structrp png_ptr, png_row_infop row_info, png_bytep row)
+{
+int rgb_error = 0;
+png_debug(1, "in png_do_rgb_to_gray");
+if (!(row_info->color_type & PNG_COLOR_MASK_PALETTE) &&
+(row_info->color_type & PNG_COLOR_MASK_COLOR))
+{
+PNG_CONST png_uint_32 rc = png_ptr->rgb_to_gray_red_coeff;
+PNG_CONST png_uint_32 gc = png_ptr->rgb_to_gray_green_coeff;
+PNG_CONST png_uint_32 bc = 32768 - rc - gc;
+PNG_CONST png_uint_32 row_width = row_info->width;
+PNG_CONST int have_alpha =
+(row_info->color_type & PNG_COLOR_MASK_ALPHA) != 0;
+if (row_info->bit_depth == 8)
+{
+#ifdef PNG_READ_GAMMA_SUPPORTED
+/* Notice that gamma to/from 1 are not necessarily inverses (if
+* there is an overall gamma correction).  Prior to 1.5.5 this code
+* checked the linearized values for equality; this doesn't match
+* the documentation, the original values must be checked.
+*/
+if (png_ptr->gamma_from_1 != NULL && png_ptr->gamma_to_1 != NULL)
+{
+png_bytep sp = row;
+png_bytep dp = row;
+png_uint_32 i;
+for (i = 0; i < row_width; i++)
+{
+png_byte red   = *(sp++);
+png_byte green = *(sp++);
+png_byte blue  = *(sp++);
+if (red != green || red != blue)
+{
+red = png_ptr->gamma_to_1[red];
+green = png_ptr->gamma_to_1[green];
+blue = png_ptr->gamma_to_1[blue];
+rgb_error |= 1;
+*(dp++) = png_ptr->gamma_from_1[
+(rc*red + gc*green + bc*blue + 16384)>>15];
+}
+else
+{
+/* If there is no overall correction the table will not be
+* set.
+*/
+if (png_ptr->gamma_table != NULL)
+red = png_ptr->gamma_table[red];
+*(dp++) = red;
+}
+if (have_alpha)
+*(dp++) = *(sp++);
+}
+}
+else
+#endif
+{
+png_bytep sp = row;
+png_bytep dp = row;
+png_uint_32 i;
+for (i = 0; i < row_width; i++)
+{
+png_byte red   = *(sp++);
+png_byte green = *(sp++);
+png_byte blue  = *(sp++);
+if (red != green || red != blue)
+{
+rgb_error |= 1;
+/* NOTE: this is the historical approach which simply
+* truncates the results.
+*/
+*(dp++) = (png_byte)((rc*red + gc*green + bc*blue)>>15);
+}
+else
+*(dp++) = red;
+if (have_alpha)
+*(dp++) = *(sp++);
+}
+}
+}
+else /* RGB bit_depth == 16 */
+{
+#ifdef PNG_READ_GAMMA_SUPPORTED
+if (png_ptr->gamma_16_to_1 != NULL && png_ptr->gamma_16_from_1 != NULL)
+{
+png_bytep sp = row;
+png_bytep dp = row;
+png_uint_32 i;
+for (i = 0; i < row_width; i++)
+{
+png_uint_16 red, green, blue, w;
+red   = (png_uint_16)(((*(sp))<<8) | *(sp + 1)); sp += 2;
+green = (png_uint_16)(((*(sp))<<8) | *(sp + 1)); sp += 2;
+blue  = (png_uint_16)(((*(sp))<<8) | *(sp + 1)); sp += 2;
+if (red == green && red == blue)
+{
+if (png_ptr->gamma_16_table != NULL)
+w = png_ptr->gamma_16_table[(red&0xff)
+>> png_ptr->gamma_shift][red>>8];
+else
+w = red;
+}
+else
+{
+png_uint_16 red_1   = png_ptr->gamma_16_to_1[(red&0xff)
+>> png_ptr->gamma_shift][red>>8];
+png_uint_16 green_1 =
+png_ptr->gamma_16_to_1[(green&0xff) >>
+png_ptr->gamma_shift][green>>8];
+png_uint_16 blue_1  = png_ptr->gamma_16_to_1[(blue&0xff)
+>> png_ptr->gamma_shift][blue>>8];
+png_uint_16 gray16  = (png_uint_16)((rc*red_1 + gc*green_1
++ bc*blue_1 + 16384)>>15);
+w = png_ptr->gamma_16_from_1[(gray16&0xff) >>
+png_ptr->gamma_shift][gray16 >> 8];
+rgb_error |= 1;
+}
+*(dp++) = (png_byte)((w>>8) & 0xff);
+*(dp++) = (png_byte)(w & 0xff);
+if (have_alpha)
+{
+*(dp++) = *(sp++);
+*(dp++) = *(sp++);
+}
+}
+}
+else
+#endif
+{
+png_bytep sp = row;
+png_bytep dp = row;
+png_uint_32 i;
+for (i = 0; i < row_width; i++)
+{
+png_uint_16 red, green, blue, gray16;
+red   = (png_uint_16)(((*(sp))<<8) | *(sp + 1)); sp += 2;
+green = (png_uint_16)(((*(sp))<<8) | *(sp + 1)); sp += 2;
+blue  = (png_uint_16)(((*(sp))<<8) | *(sp + 1)); sp += 2;
+if (red != green || red != blue)
+rgb_error |= 1;
+/* From 1.5.5 in the 16 bit case do the accurate conversion even
+* in the 'fast' case - this is because this is where the code
+* ends up when handling linear 16 bit data.
+*/
+gray16  = (png_uint_16)((rc*red + gc*green + bc*blue + 16384) >>
+15);
+*(dp++) = (png_byte)((gray16>>8) & 0xff);
+*(dp++) = (png_byte)(gray16 & 0xff);
+if (have_alpha)
+{
+*(dp++) = *(sp++);
+*(dp++) = *(sp++);
+}
+}
+}
+}
+row_info->channels = (png_byte)(row_info->channels - 2);
+row_info->color_type = (png_byte)(row_info->color_type &
+~PNG_COLOR_MASK_COLOR);
+row_info->pixel_depth = (png_byte)(row_info->channels *
+row_info->bit_depth);
+row_info->rowbytes = PNG_ROWBYTES(row_info->pixel_depth, row_width);
+}
+return rgb_error;
+}
+#endif
+#if defined(PNG_READ_BACKGROUND_SUPPORTED) ||\
+defined(PNG_READ_ALPHA_MODE_SUPPORTED)
+/* Replace any alpha or transparency with the supplied background color.
+* "background" is already in the screen gamma, while "background_1" is
+* at a gamma of 1.0.  Paletted files have already been taken care of.
+*/
+static void
+png_do_compose(png_row_infop row_info, png_bytep row, png_structrp png_ptr)
+{
+#ifdef PNG_READ_GAMMA_SUPPORTED
+png_const_bytep gamma_table = png_ptr->gamma_table;
+png_const_bytep gamma_from_1 = png_ptr->gamma_from_1;
+png_const_bytep gamma_to_1 = png_ptr->gamma_to_1;
+png_const_uint_16pp gamma_16 = png_ptr->gamma_16_table;
+png_const_uint_16pp gamma_16_from_1 = png_ptr->gamma_16_from_1;
+png_const_uint_16pp gamma_16_to_1 = png_ptr->gamma_16_to_1;
+int gamma_shift = png_ptr->gamma_shift;
+int optimize = (png_ptr->flags & PNG_FLAG_OPTIMIZE_ALPHA) != 0;
+#endif
+png_bytep sp;
+png_uint_32 i;
+png_uint_32 row_width = row_info->width;
+int shift;
+png_debug(1, "in png_do_compose");
+{
+switch (row_info->color_type)
+{
+case PNG_COLOR_TYPE_GRAY:
+{
+switch (row_info->bit_depth)
+{
+case 1:
+{
+sp = row;
+shift = 7;
+for (i = 0; i < row_width; i++)
+{
+if ((png_uint_16)((*sp >> shift) & 0x01)
+== png_ptr->trans_color.gray)
+{
+unsigned int tmp = *sp & (0x7f7f >> (7 - shift));
+tmp |= png_ptr->background.gray << shift;
+*sp = (png_byte)(tmp & 0xff);
+}
+if (!shift)
+{
+shift = 7;
+sp++;
+}
+else
+shift--;
+}
+break;
+}
+case 2:
+{
+#ifdef PNG_READ_GAMMA_SUPPORTED
+if (gamma_table != NULL)
+{
+sp = row;
+shift = 6;
+for (i = 0; i < row_width; i++)
+{
+if ((png_uint_16)((*sp >> shift) & 0x03)
+== png_ptr->trans_color.gray)
+{
+unsigned int tmp = *sp & (0x3f3f >> (6 - shift));
+tmp |= png_ptr->background.gray << shift;
+*sp = (png_byte)(tmp & 0xff);
+}
+else
+{
+unsigned int p = (*sp >> shift) & 0x03;
+unsigned int g = (gamma_table [p | (p << 2) |
+(p << 4) | (p << 6)] >> 6) & 0x03;
+unsigned int tmp = *sp & (0x3f3f >> (6 - shift));
+tmp |= g << shift;
+*sp = (png_byte)(tmp & 0xff);
+}
+if (!shift)
+{
+shift = 6;
+sp++;
+}
+else
+shift -= 2;
+}
+}
+else
+#endif
+{
+sp = row;
+shift = 6;
+for (i = 0; i < row_width; i++)
+{
+if ((png_uint_16)((*sp >> shift) & 0x03)
+== png_ptr->trans_color.gray)
+{
+unsigned int tmp = *sp & (0x3f3f >> (6 - shift));
+tmp |= png_ptr->background.gray << shift;
+*sp = (png_byte)(tmp & 0xff);
+}
+if (!shift)
+{
+shift = 6;
+sp++;
+}
+else
+shift -= 2;
+}
+}
+break;
+}
+case 4:
+{
+#ifdef PNG_READ_GAMMA_SUPPORTED
+if (gamma_table != NULL)
+{
+sp = row;
+shift = 4;
+for (i = 0; i < row_width; i++)
+{
+if ((png_uint_16)((*sp >> shift) & 0x0f)
+== png_ptr->trans_color.gray)
+{
+unsigned int tmp = *sp & (0xf0f >> (4 - shift));
+tmp |= png_ptr->background.gray << shift;
+*sp = (png_byte)(tmp & 0xff);
+}
+else
+{
+unsigned int p = (*sp >> shift) & 0x0f;
+unsigned int g = (gamma_table[p | (p << 4)] >> 4) &
+0x0f;
+unsigned int tmp = *sp & (0xf0f >> (4 - shift));
+tmp |= g << shift;
+*sp = (png_byte)(tmp & 0xff);
+}
+if (!shift)
+{
+shift = 4;
+sp++;
+}
+else
+shift -= 4;
+}
+}
+else
+#endif
+{
+sp = row;
+shift = 4;
+for (i = 0; i < row_width; i++)
+{
+if ((png_uint_16)((*sp >> shift) & 0x0f)
+== png_ptr->trans_color.gray)
+{
+unsigned int tmp = *sp & (0xf0f >> (4 - shift));
+tmp |= png_ptr->background.gray << shift;
+*sp = (png_byte)(tmp & 0xff);
+}
+if (!shift)
+{
+shift = 4;
+sp++;
+}
+else
+shift -= 4;
+}
+}
+break;
+}
+case 8:
+{
+#ifdef PNG_READ_GAMMA_SUPPORTED
+if (gamma_table != NULL)
+{
+sp = row;
+for (i = 0; i < row_width; i++, sp++)
+{
+if (*sp == png_ptr->trans_color.gray)
+*sp = (png_byte)png_ptr->background.gray;
+else
+*sp = gamma_table[*sp];
+}
+}
+else
+#endif
+{
+sp = row;
+for (i = 0; i < row_width; i++, sp++)
+{
+if (*sp == png_ptr->trans_color.gray)
+*sp = (png_byte)png_ptr->background.gray;
+}
+}
+break;
+}
+case 16:
+{
+#ifdef PNG_READ_GAMMA_SUPPORTED
+if (gamma_16 != NULL)
+{
+sp = row;
+for (i = 0; i < row_width; i++, sp += 2)
+{
+png_uint_16 v;
+v = (png_uint_16)(((*sp) << 8) + *(sp + 1));
+if (v == png_ptr->trans_color.gray)
+{
+/* Background is already in screen gamma */
+*sp = (png_byte)((png_ptr->background.gray >> 8)
+& 0xff);
+*(sp + 1) = (png_byte)(png_ptr->background.gray
+& 0xff);
+}
+else
+{
+v = gamma_16[*(sp + 1) >> gamma_shift][*sp];
+*sp = (png_byte)((v >> 8) & 0xff);
+*(sp + 1) = (png_byte)(v & 0xff);
+}
+}
+}
+else
+#endif
+{
+sp = row;
+for (i = 0; i < row_width; i++, sp += 2)
+{
+png_uint_16 v;
+v = (png_uint_16)(((*sp) << 8) + *(sp + 1));
+if (v == png_ptr->trans_color.gray)
+{
+*sp = (png_byte)((png_ptr->background.gray >> 8)
+& 0xff);
+*(sp + 1) = (png_byte)(png_ptr->background.gray
+& 0xff);
+}
+}
+}
+break;
+}
+default:
+break;
+}
+break;
+}
+case PNG_COLOR_TYPE_RGB:
+{
+if (row_info->bit_depth == 8)
+{
+#ifdef PNG_READ_GAMMA_SUPPORTED
+if (gamma_table != NULL)
+{
+sp = row;
+for (i = 0; i < row_width; i++, sp += 3)
+{
+if (*sp == png_ptr->trans_color.red &&
+*(sp + 1) == png_ptr->trans_color.green &&
+*(sp + 2) == png_ptr->trans_color.blue)
+{
+*sp = (png_byte)png_ptr->background.red;
+*(sp + 1) = (png_byte)png_ptr->background.green;
+*(sp + 2) = (png_byte)png_ptr->background.blue;
+}
+else
+{
+*sp = gamma_table[*sp];
+*(sp + 1) = gamma_table[*(sp + 1)];
+*(sp + 2) = gamma_table[*(sp + 2)];
+}
+}
+}
+else
+#endif
+{
+sp = row;
+for (i = 0; i < row_width; i++, sp += 3)
+{
+if (*sp == png_ptr->trans_color.red &&
+*(sp + 1) == png_ptr->trans_color.green &&
+*(sp + 2) == png_ptr->trans_color.blue)
+{
+*sp = (png_byte)png_ptr->background.red;
+*(sp + 1) = (png_byte)png_ptr->background.green;
+*(sp + 2) = (png_byte)png_ptr->background.blue;
+}
+}
+}
+}
+else /* if (row_info->bit_depth == 16) */
+{
+#ifdef PNG_READ_GAMMA_SUPPORTED
+if (gamma_16 != NULL)
+{
+sp = row;
+for (i = 0; i < row_width; i++, sp += 6)
+{
+png_uint_16 r = (png_uint_16)(((*sp) << 8) + *(sp + 1));
+png_uint_16 g = (png_uint_16)(((*(sp + 2)) << 8)
++ *(sp + 3));
+png_uint_16 b = (png_uint_16)(((*(sp + 4)) << 8)
++ *(sp + 5));
+if (r == png_ptr->trans_color.red &&
+g == png_ptr->trans_color.green &&
+b == png_ptr->trans_color.blue)
+{
+/* Background is already in screen gamma */
+*sp = (png_byte)((png_ptr->background.red >> 8) & 0xff);
+*(sp + 1) = (png_byte)(png_ptr->background.red & 0xff);
+*(sp + 2) = (png_byte)((png_ptr->background.green >> 8)
+& 0xff);
+*(sp + 3) = (png_byte)(png_ptr->background.green
+& 0xff);
+*(sp + 4) = (png_byte)((png_ptr->background.blue >> 8)
+& 0xff);
+*(sp + 5) = (png_byte)(png_ptr->background.blue & 0xff);
+}
+else
+{
+png_uint_16 v = gamma_16[*(sp + 1) >> gamma_shift][*sp];
+*sp = (png_byte)((v >> 8) & 0xff);
+*(sp + 1) = (png_byte)(v & 0xff);
+v = gamma_16[*(sp + 3) >> gamma_shift][*(sp + 2)];
+*(sp + 2) = (png_byte)((v >> 8) & 0xff);
+*(sp + 3) = (png_byte)(v & 0xff);
+v = gamma_16[*(sp + 5) >> gamma_shift][*(sp + 4)];
+*(sp + 4) = (png_byte)((v >> 8) & 0xff);
+*(sp + 5) = (png_byte)(v & 0xff);
+}
+}
+}
+else
+#endif
+{
+sp = row;
+for (i = 0; i < row_width; i++, sp += 6)
+{
+png_uint_16 r = (png_uint_16)(((*sp) << 8) + *(sp + 1));
+png_uint_16 g = (png_uint_16)(((*(sp + 2)) << 8)
++ *(sp + 3));
+png_uint_16 b = (png_uint_16)(((*(sp + 4)) << 8)
++ *(sp + 5));
+if (r == png_ptr->trans_color.red &&
+g == png_ptr->trans_color.green &&
+b == png_ptr->trans_color.blue)
+{
+*sp = (png_byte)((png_ptr->background.red >> 8) & 0xff);
+*(sp + 1) = (png_byte)(png_ptr->background.red & 0xff);
+*(sp + 2) = (png_byte)((png_ptr->background.green >> 8)
+& 0xff);
+*(sp + 3) = (png_byte)(png_ptr->background.green
+& 0xff);
+*(sp + 4) = (png_byte)((png_ptr->background.blue >> 8)
+& 0xff);
+*(sp + 5) = (png_byte)(png_ptr->background.blue & 0xff);
+}
+}
+}
+}
+break;
+}
+case PNG_COLOR_TYPE_GRAY_ALPHA:
+{
+if (row_info->bit_depth == 8)
+{
+#ifdef PNG_READ_GAMMA_SUPPORTED
+if (gamma_to_1 != NULL && gamma_from_1 != NULL &&
+gamma_table != NULL)
+{
+sp = row;
+for (i = 0; i < row_width; i++, sp += 2)
+{
+png_uint_16 a = *(sp + 1);
+if (a == 0xff)
+*sp = gamma_table[*sp];
+else if (a == 0)
+{
+/* Background is already in screen gamma */
+*sp = (png_byte)png_ptr->background.gray;
+}
+else
+{
+png_byte v, w;
+v = gamma_to_1[*sp];
+png_composite(w, v, a, png_ptr->background_1.gray);
+if (!optimize)
+w = gamma_from_1[w];
+*sp = w;
+}
+}
+}
+else
+#endif
+{
+sp = row;
+for (i = 0; i < row_width; i++, sp += 2)
+{
+png_byte a = *(sp + 1);
+if (a == 0)
+*sp = (png_byte)png_ptr->background.gray;
+else if (a < 0xff)
+png_composite(*sp, *sp, a, png_ptr->background.gray);
+}
+}
+}
+else /* if (png_ptr->bit_depth == 16) */
+{
+#ifdef PNG_READ_GAMMA_SUPPORTED
+if (gamma_16 != NULL && gamma_16_from_1 != NULL &&
+gamma_16_to_1 != NULL)
+{
+sp = row;
+for (i = 0; i < row_width; i++, sp += 4)
+{
+png_uint_16 a = (png_uint_16)(((*(sp + 2)) << 8)
++ *(sp + 3));
+if (a == (png_uint_16)0xffff)
+{
+png_uint_16 v;
+v = gamma_16[*(sp + 1) >> gamma_shift][*sp];
+*sp = (png_byte)((v >> 8) & 0xff);
+*(sp + 1) = (png_byte)(v & 0xff);
+}
+else if (a == 0)
+{
+/* Background is already in screen gamma */
+*sp = (png_byte)((png_ptr->background.gray >> 8)
+& 0xff);
+*(sp + 1) = (png_byte)(png_ptr->background.gray & 0xff);
+}
+else
+{
+png_uint_16 g, v, w;
+g = gamma_16_to_1[*(sp + 1) >> gamma_shift][*sp];
+png_composite_16(v, g, a, png_ptr->background_1.gray);
+if (optimize)
+w = v;
+else
+w = gamma_16_from_1[(v&0xff) >> gamma_shift][v >> 8];
+*sp = (png_byte)((w >> 8) & 0xff);
+*(sp + 1) = (png_byte)(w & 0xff);
+}
+}
+}
+else
+#endif
+{
+sp = row;
+for (i = 0; i < row_width; i++, sp += 4)
+{
+png_uint_16 a = (png_uint_16)(((*(sp + 2)) << 8)
++ *(sp + 3));
+if (a == 0)
+{
+*sp = (png_byte)((png_ptr->background.gray >> 8)
+& 0xff);
+*(sp + 1) = (png_byte)(png_ptr->background.gray & 0xff);
+}
+else if (a < 0xffff)
+{
+png_uint_16 g, v;
+g = (png_uint_16)(((*sp) << 8) + *(sp + 1));
+png_composite_16(v, g, a, png_ptr->background.gray);
+*sp = (png_byte)((v >> 8) & 0xff);
+*(sp + 1) = (png_byte)(v & 0xff);
+}
+}
+}
+}
+break;
+}
+case PNG_COLOR_TYPE_RGB_ALPHA:
+{
+if (row_info->bit_depth == 8)
+{
+#ifdef PNG_READ_GAMMA_SUPPORTED
+if (gamma_to_1 != NULL && gamma_from_1 != NULL &&
+gamma_table != NULL)
+{
+sp = row;
+for (i = 0; i < row_width; i++, sp += 4)
+{
+png_byte a = *(sp + 3);
+if (a == 0xff)
+{
+*sp = gamma_table[*sp];
+*(sp + 1) = gamma_table[*(sp + 1)];
+*(sp + 2) = gamma_table[*(sp + 2)];
+}
+else if (a == 0)
+{
+/* Background is already in screen gamma */
+*sp = (png_byte)png_ptr->background.red;
+*(sp + 1) = (png_byte)png_ptr->background.green;
+*(sp + 2) = (png_byte)png_ptr->background.blue;
+}
+else
+{
+png_byte v, w;
+v = gamma_to_1[*sp];
+png_composite(w, v, a, png_ptr->background_1.red);
+if (!optimize) w = gamma_from_1[w];
+*sp = w;
+v = gamma_to_1[*(sp + 1)];
+png_composite(w, v, a, png_ptr->background_1.green);
+if (!optimize) w = gamma_from_1[w];
+*(sp + 1) = w;
+v = gamma_to_1[*(sp + 2)];
+png_composite(w, v, a, png_ptr->background_1.blue);
+if (!optimize) w = gamma_from_1[w];
+*(sp + 2) = w;
+}
+}
+}
+else
+#endif
+{
+sp = row;
+for (i = 0; i < row_width; i++, sp += 4)
+{
+png_byte a = *(sp + 3);
+if (a == 0)
+{
+*sp = (png_byte)png_ptr->background.red;
+*(sp + 1) = (png_byte)png_ptr->background.green;
+*(sp + 2) = (png_byte)png_ptr->background.blue;
+}
+else if (a < 0xff)
+{
+png_composite(*sp, *sp, a, png_ptr->background.red);
+png_composite(*(sp + 1), *(sp + 1), a,
+png_ptr->background.green);
+png_composite(*(sp + 2), *(sp + 2), a,
+png_ptr->background.blue);
+}
+}
+}
+}
+else /* if (row_info->bit_depth == 16) */
+{
+#ifdef PNG_READ_GAMMA_SUPPORTED
+if (gamma_16 != NULL && gamma_16_from_1 != NULL &&
+gamma_16_to_1 != NULL)
+{
+sp = row;
+for (i = 0; i < row_width; i++, sp += 8)
+{
+png_uint_16 a = (png_uint_16)(((png_uint_16)(*(sp + 6))
+<< 8) + (png_uint_16)(*(sp + 7)));
+if (a == (png_uint_16)0xffff)
+{
+png_uint_16 v;
+v = gamma_16[*(sp + 1) >> gamma_shift][*sp];
+*sp = (png_byte)((v >> 8) & 0xff);
+*(sp + 1) = (png_byte)(v & 0xff);
+v = gamma_16[*(sp + 3) >> gamma_shift][*(sp + 2)];
+*(sp + 2) = (png_byte)((v >> 8) & 0xff);
+*(sp + 3) = (png_byte)(v & 0xff);
+v = gamma_16[*(sp + 5) >> gamma_shift][*(sp + 4)];
+*(sp + 4) = (png_byte)((v >> 8) & 0xff);
+*(sp + 5) = (png_byte)(v & 0xff);
+}
+else if (a == 0)
+{
+/* Background is already in screen gamma */
+*sp = (png_byte)((png_ptr->background.red >> 8) & 0xff);
+*(sp + 1) = (png_byte)(png_ptr->background.red & 0xff);
+*(sp + 2) = (png_byte)((png_ptr->background.green >> 8)
+& 0xff);
+*(sp + 3) = (png_byte)(png_ptr->background.green
+& 0xff);
+*(sp + 4) = (png_byte)((png_ptr->background.blue >> 8)
+& 0xff);
+*(sp + 5) = (png_byte)(png_ptr->background.blue & 0xff);
+}
+else
+{
+png_uint_16 v, w;
+v = gamma_16_to_1[*(sp + 1) >> gamma_shift][*sp];
+png_composite_16(w, v, a, png_ptr->background_1.red);
+if (!optimize)
+w = gamma_16_from_1[((w&0xff) >> gamma_shift)][w >>
+8];
+*sp = (png_byte)((w >> 8) & 0xff);
+*(sp + 1) = (png_byte)(w & 0xff);
+v = gamma_16_to_1[*(sp + 3) >> gamma_shift][*(sp + 2)];
+png_composite_16(w, v, a, png_ptr->background_1.green);
+if (!optimize)
+w = gamma_16_from_1[((w&0xff) >> gamma_shift)][w >>
+8];
+*(sp + 2) = (png_byte)((w >> 8) & 0xff);
+*(sp + 3) = (png_byte)(w & 0xff);
+v = gamma_16_to_1[*(sp + 5) >> gamma_shift][*(sp + 4)];
+png_composite_16(w, v, a, png_ptr->background_1.blue);
+if (!optimize)
+w = gamma_16_from_1[((w&0xff) >> gamma_shift)][w >>
+8];
+*(sp + 4) = (png_byte)((w >> 8) & 0xff);
+*(sp + 5) = (png_byte)(w & 0xff);
+}
+}
+}
+else
+#endif
+{
+sp = row;
+for (i = 0; i < row_width; i++, sp += 8)
+{
+png_uint_16 a = (png_uint_16)(((png_uint_16)(*(sp + 6))
+<< 8) + (png_uint_16)(*(sp + 7)));
+if (a == 0)
+{
+*sp = (png_byte)((png_ptr->background.red >> 8) & 0xff);
+*(sp + 1) = (png_byte)(png_ptr->background.red & 0xff);
+*(sp + 2) = (png_byte)((png_ptr->background.green >> 8)
+& 0xff);
+*(sp + 3) = (png_byte)(png_ptr->background.green
+& 0xff);
+*(sp + 4) = (png_byte)((png_ptr->background.blue >> 8)
+& 0xff);
+*(sp + 5) = (png_byte)(png_ptr->background.blue & 0xff);
+}
+else if (a < 0xffff)
+{
+png_uint_16 v;
+png_uint_16 r = (png_uint_16)(((*sp) << 8) + *(sp + 1));
+png_uint_16 g = (png_uint_16)(((*(sp + 2)) << 8)
++ *(sp + 3));
+png_uint_16 b = (png_uint_16)(((*(sp + 4)) << 8)
++ *(sp + 5));
+png_composite_16(v, r, a, png_ptr->background.red);
+*sp = (png_byte)((v >> 8) & 0xff);
+*(sp + 1) = (png_byte)(v & 0xff);
+png_composite_16(v, g, a, png_ptr->background.green);
+*(sp + 2) = (png_byte)((v >> 8) & 0xff);
+*(sp + 3) = (png_byte)(v & 0xff);
+png_composite_16(v, b, a, png_ptr->background.blue);
+*(sp + 4) = (png_byte)((v >> 8) & 0xff);
+*(sp + 5) = (png_byte)(v & 0xff);
+}
+}
+}
+}
+break;
+}
+default:
+break;
+}
+}
+}
+#endif /* PNG_READ_BACKGROUND_SUPPORTED || PNG_READ_ALPHA_MODE_SUPPORTED */
+#ifdef PNG_READ_GAMMA_SUPPORTED
+/* Gamma correct the image, avoiding the alpha channel.  Make sure
+* you do this after you deal with the transparency issue on grayscale
+* or RGB images. If your bit depth is 8, use gamma_table, if it
+* is 16, use gamma_16_table and gamma_shift.  Build these with
+* build_gamma_table().
+*/
+static void
+png_do_gamma(png_row_infop row_info, png_bytep row, png_structrp png_ptr)
+{
+png_const_bytep gamma_table = png_ptr->gamma_table;
+png_const_uint_16pp gamma_16_table = png_ptr->gamma_16_table;
+int gamma_shift = png_ptr->gamma_shift;
+png_bytep sp;
+png_uint_32 i;
+png_uint_32 row_width=row_info->width;
+png_debug(1, "in png_do_gamma");
+if (((row_info->bit_depth <= 8 && gamma_table != NULL) ||
+(row_info->bit_depth == 16 && gamma_16_table != NULL)))
+{
+switch (row_info->color_type)
+{
+case PNG_COLOR_TYPE_RGB:
+{
+if (row_info->bit_depth == 8)
+{
+sp = row;
+for (i = 0; i < row_width; i++)
+{
+*sp = gamma_table[*sp];
+sp++;
+*sp = gamma_table[*sp];
+sp++;
+*sp = gamma_table[*sp];
+sp++;
+}
+}
+else /* if (row_info->bit_depth == 16) */
+{
+sp = row;
+for (i = 0; i < row_width; i++)
+{
+png_uint_16 v;
+v = gamma_16_table[*(sp + 1) >> gamma_shift][*sp];
+*sp = (png_byte)((v >> 8) & 0xff);
+*(sp + 1) = (png_byte)(v & 0xff);
+sp += 2;
+v = gamma_16_table[*(sp + 1) >> gamma_shift][*sp];
+*sp = (png_byte)((v >> 8) & 0xff);
+*(sp + 1) = (png_byte)(v & 0xff);
+sp += 2;
+v = gamma_16_table[*(sp + 1) >> gamma_shift][*sp];
+*sp = (png_byte)((v >> 8) & 0xff);
+*(sp + 1) = (png_byte)(v & 0xff);
+sp += 2;
+}
+}
+break;
+}
+case PNG_COLOR_TYPE_RGB_ALPHA:
+{
+if (row_info->bit_depth == 8)
+{
+sp = row;
+for (i = 0; i < row_width; i++)
+{
+*sp = gamma_table[*sp];
+sp++;
+*sp = gamma_table[*sp];
+sp++;
+*sp = gamma_table[*sp];
+sp++;
+sp++;
+}
+}
+else /* if (row_info->bit_depth == 16) */
+{
+sp = row;
+for (i = 0; i < row_width; i++)
+{
+png_uint_16 v = gamma_16_table[*(sp + 1) >> gamma_shift][*sp];
+*sp = (png_byte)((v >> 8) & 0xff);
+*(sp + 1) = (png_byte)(v & 0xff);
+sp += 2;
+v = gamma_16_table[*(sp + 1) >> gamma_shift][*sp];
+*sp = (png_byte)((v >> 8) & 0xff);
+*(sp + 1) = (png_byte)(v & 0xff);
+sp += 2;
+v = gamma_16_table[*(sp + 1) >> gamma_shift][*sp];
+*sp = (png_byte)((v >> 8) & 0xff);
+*(sp + 1) = (png_byte)(v & 0xff);
+sp += 4;
+}
+}
+break;
+}
+case PNG_COLOR_TYPE_GRAY_ALPHA:
+{
+if (row_info->bit_depth == 8)
+{
+sp = row;
+for (i = 0; i < row_width; i++)
+{
+*sp = gamma_table[*sp];
+sp += 2;
+}
+}
+else /* if (row_info->bit_depth == 16) */
+{
+sp = row;
+for (i = 0; i < row_width; i++)
+{
+png_uint_16 v = gamma_16_table[*(sp + 1) >> gamma_shift][*sp];
+*sp = (png_byte)((v >> 8) & 0xff);
+*(sp + 1) = (png_byte)(v & 0xff);
+sp += 4;
+}
+}
+break;
+}
+case PNG_COLOR_TYPE_GRAY:
+{
+if (row_info->bit_depth == 2)
+{
+sp = row;
+for (i = 0; i < row_width; i += 4)
+{
+int a = *sp & 0xc0;
+int b = *sp & 0x30;
+int c = *sp & 0x0c;
+int d = *sp & 0x03;
+*sp = (png_byte)(
+((((int)gamma_table[a|(a>>2)|(a>>4)|(a>>6)])   ) & 0xc0)|
+((((int)gamma_table[(b<<2)|b|(b>>2)|(b>>4)])>>2) & 0x30)|
+((((int)gamma_table[(c<<4)|(c<<2)|c|(c>>2)])>>4) & 0x0c)|
+((((int)gamma_table[(d<<6)|(d<<4)|(d<<2)|d])>>6) ));
+sp++;
+}
+}
+if (row_info->bit_depth == 4)
+{
+sp = row;
+for (i = 0; i < row_width; i += 2)
+{
+int msb = *sp & 0xf0;
+int lsb = *sp & 0x0f;
+*sp = (png_byte)((((int)gamma_table[msb | (msb >> 4)]) & 0xf0)
+| (((int)gamma_table[(lsb << 4) | lsb]) >> 4));
+sp++;
+}
+}
+else if (row_info->bit_depth == 8)
+{
+sp = row;
+for (i = 0; i < row_width; i++)
+{
+*sp = gamma_table[*sp];
+sp++;
+}
+}
+else if (row_info->bit_depth == 16)
+{
+sp = row;
+for (i = 0; i < row_width; i++)
+{
+png_uint_16 v = gamma_16_table[*(sp + 1) >> gamma_shift][*sp];
+*sp = (png_byte)((v >> 8) & 0xff);
+*(sp + 1) = (png_byte)(v & 0xff);
+sp += 2;
+}
+}
+break;
+}
+default:
+break;
+}
+}
+}
+#endif
+#ifdef PNG_READ_ALPHA_MODE_SUPPORTED
+/* Encode the alpha channel to the output gamma (the input channel is always
+* linear.)  Called only with color types that have an alpha channel.  Needs the
+* from_1 tables.
+*/
+static void
+png_do_encode_alpha(png_row_infop row_info, png_bytep row, png_structrp png_ptr)
+{
+png_uint_32 row_width = row_info->width;
+png_debug(1, "in png_do_encode_alpha");
+if (row_info->color_type & PNG_COLOR_MASK_ALPHA)
+{
+if (row_info->bit_depth == 8)
+{
+PNG_CONST png_bytep table = png_ptr->gamma_from_1;
+if (table != NULL)
+{
+PNG_CONST int step =
+(row_info->color_type & PNG_COLOR_MASK_COLOR) ? 4 : 2;
+/* The alpha channel is the last component: */
+row += step - 1;
+for (; row_width > 0; --row_width, row += step)
+*row = table[*row];
+return;
+}
+}
+else if (row_info->bit_depth == 16)
+{
+PNG_CONST png_uint_16pp table = png_ptr->gamma_16_from_1;
+PNG_CONST int gamma_shift = png_ptr->gamma_shift;
+if (table != NULL)
+{
+PNG_CONST int step =
+(row_info->color_type & PNG_COLOR_MASK_COLOR) ? 8 : 4;
+/* The alpha channel is the last component: */
+row += step - 2;
+for (; row_width > 0; --row_width, row += step)
+{
+png_uint_16 v;
+v = table[*(row + 1) >> gamma_shift][*row];
+*row = (png_byte)((v >> 8) & 0xff);
+*(row + 1) = (png_byte)(v & 0xff);
+}
+return;
+}
+}
+}
+/* Only get to here if called with a weird row_info; no harm has been done,
+* so just issue a warning.
+*/
+png_warning(png_ptr, "png_do_encode_alpha: unexpected call");
+}
+#endif
+#ifdef PNG_READ_EXPAND_SUPPORTED
+/* Expands a palette row to an RGB or RGBA row depending
+* upon whether you supply trans and num_trans.
+*/
+static void
+png_do_expand_palette(png_row_infop row_info, png_bytep row,
+png_const_colorp palette, png_const_bytep trans_alpha, int num_trans)
+{
+int shift, value;
+png_bytep sp, dp;
+png_uint_32 i;
+png_uint_32 row_width=row_info->width;
+png_debug(1, "in png_do_expand_palette");
+if (row_info->color_type == PNG_COLOR_TYPE_PALETTE)
+{
+if (row_info->bit_depth < 8)
+{
+switch (row_info->bit_depth)
+{
+case 1:
+{
+sp = row + (png_size_t)((row_width - 1) >> 3);
+dp = row + (png_size_t)row_width - 1;
+shift = 7 - (int)((row_width + 7) & 0x07);
+for (i = 0; i < row_width; i++)
+{
+if ((*sp >> shift) & 0x01)
+*dp = 1;
+else
+*dp = 0;
+if (shift == 7)
+{
+shift = 0;
+sp--;
+}
+else
+shift++;
+dp--;
+}
+break;
+}
+case 2:
+{
+sp = row + (png_size_t)((row_width - 1) >> 2);
+dp = row + (png_size_t)row_width - 1;
+shift = (int)((3 - ((row_width + 3) & 0x03)) << 1);
+for (i = 0; i < row_width; i++)
+{
+value = (*sp >> shift) & 0x03;
+*dp = (png_byte)value;
+if (shift == 6)
+{
+shift = 0;
+sp--;
+}
+else
+shift += 2;
+dp--;
+}
+break;
+}
+case 4:
+{
+sp = row + (png_size_t)((row_width - 1) >> 1);
+dp = row + (png_size_t)row_width - 1;
+shift = (int)((row_width & 0x01) << 2);
+for (i = 0; i < row_width; i++)
+{
+value = (*sp >> shift) & 0x0f;
+*dp = (png_byte)value;
+if (shift == 4)
+{
+shift = 0;
+sp--;
+}
+else
+shift += 4;
+dp--;
+}
+break;
+}
+default:
+break;
+}
+row_info->bit_depth = 8;
+row_info->pixel_depth = 8;
+row_info->rowbytes = row_width;
+}
+if (row_info->bit_depth == 8)
+{
+{
+if (num_trans > 0)
+{
+sp = row + (png_size_t)row_width - 1;
+dp = row + (png_size_t)(row_width << 2) - 1;
+for (i = 0; i < row_width; i++)
+{
+if ((int)(*sp) >= num_trans)
+*dp-- = 0xff;
+else
+*dp-- = trans_alpha[*sp];
+*dp-- = palette[*sp].blue;
+*dp-- = palette[*sp].green;
+*dp-- = palette[*sp].red;
+sp--;
+}
+row_info->bit_depth = 8;
+row_info->pixel_depth = 32;
+row_info->rowbytes = row_width * 4;
+row_info->color_type = 6;
+row_info->channels = 4;
+}
+else
+{
+sp = row + (png_size_t)row_width - 1;
+dp = row + (png_size_t)(row_width * 3) - 1;
+for (i = 0; i < row_width; i++)
+{
+*dp-- = palette[*sp].blue;
+*dp-- = palette[*sp].green;
+*dp-- = palette[*sp].red;
+sp--;
+}
+row_info->bit_depth = 8;
+row_info->pixel_depth = 24;
+row_info->rowbytes = row_width * 3;
+row_info->color_type = 2;
+row_info->channels = 3;
+}
+}
+}
+}
+}
+/* If the bit depth < 8, it is expanded to 8.  Also, if the already
+* expanded transparency value is supplied, an alpha channel is built.
+*/
+static void
+png_do_expand(png_row_infop row_info, png_bytep row,
+png_const_color_16p trans_color)
+{
+int shift, value;
+png_bytep sp, dp;
+png_uint_32 i;
+png_uint_32 row_width=row_info->width;
+png_debug(1, "in png_do_expand");
+{
+if (row_info->color_type == PNG_COLOR_TYPE_GRAY)
+{
+unsigned int gray = trans_color ? trans_color->gray : 0;
+if (row_info->bit_depth < 8)
+{
+switch (row_info->bit_depth)
+{
+case 1:
+{
+gray = (gray & 0x01) * 0xff;
+sp = row + (png_size_t)((row_width - 1) >> 3);
+dp = row + (png_size_t)row_width - 1;
+shift = 7 - (int)((row_width + 7) & 0x07);
+for (i = 0; i < row_width; i++)
+{
+if ((*sp >> shift) & 0x01)
+*dp = 0xff;
+else
+*dp = 0;
+if (shift == 7)
+{
+shift = 0;
+sp--;
+}
+else
+shift++;
+dp--;
+}
+break;
+}
+case 2:
+{
+gray = (gray & 0x03) * 0x55;
+sp = row + (png_size_t)((row_width - 1) >> 2);
+dp = row + (png_size_t)row_width - 1;
+shift = (int)((3 - ((row_width + 3) & 0x03)) << 1);
+for (i = 0; i < row_width; i++)
+{
+value = (*sp >> shift) & 0x03;
+*dp = (png_byte)(value | (value << 2) | (value << 4) |
+(value << 6));
+if (shift == 6)
+{
+shift = 0;
+sp--;
+}
+else
+shift += 2;
+dp--;
+}
+break;
+}
+case 4:
+{
+gray = (gray & 0x0f) * 0x11;
+sp = row + (png_size_t)((row_width - 1) >> 1);
+dp = row + (png_size_t)row_width - 1;
+shift = (int)((1 - ((row_width + 1) & 0x01)) << 2);
+for (i = 0; i < row_width; i++)
+{
+value = (*sp >> shift) & 0x0f;
+*dp = (png_byte)(value | (value << 4));
+if (shift == 4)
+{
+shift = 0;
+sp--;
+}
+else
+shift = 4;
+dp--;
+}
+break;
+}
+default:
+break;
+}
+row_info->bit_depth = 8;
+row_info->pixel_depth = 8;
+row_info->rowbytes = row_width;
+}
+if (trans_color != NULL)
+{
+if (row_info->bit_depth == 8)
+{
+gray = gray & 0xff;
+sp = row + (png_size_t)row_width - 1;
+dp = row + (png_size_t)(row_width << 1) - 1;
+for (i = 0; i < row_width; i++)
+{
+if (*sp == gray)
+*dp-- = 0;
+else
+*dp-- = 0xff;
+*dp-- = *sp--;
+}
+}
+else if (row_info->bit_depth == 16)
+{
+unsigned int gray_high = (gray >> 8) & 0xff;
+unsigned int gray_low = gray & 0xff;
+sp = row + row_info->rowbytes - 1;
+dp = row + (row_info->rowbytes << 1) - 1;
+for (i = 0; i < row_width; i++)
+{
+if (*(sp - 1) == gray_high && *(sp) == gray_low)
+{
+*dp-- = 0;
+*dp-- = 0;
+}
+else
+{
+*dp-- = 0xff;
+*dp-- = 0xff;
+}
+*dp-- = *sp--;
+*dp-- = *sp--;
+}
+}
+row_info->color_type = PNG_COLOR_TYPE_GRAY_ALPHA;
+row_info->channels = 2;
+row_info->pixel_depth = (png_byte)(row_info->bit_depth << 1);
+row_info->rowbytes = PNG_ROWBYTES(row_info->pixel_depth,
+row_width);
+}
+}
+else if (row_info->color_type == PNG_COLOR_TYPE_RGB && trans_color)
+{
+if (row_info->bit_depth == 8)
+{
+png_byte red = (png_byte)(trans_color->red & 0xff);
+png_byte green = (png_byte)(trans_color->green & 0xff);
+png_byte blue = (png_byte)(trans_color->blue & 0xff);
+sp = row + (png_size_t)row_info->rowbytes - 1;
+dp = row + (png_size_t)(row_width << 2) - 1;
+for (i = 0; i < row_width; i++)
+{
+if (*(sp - 2) == red && *(sp - 1) == green && *(sp) == blue)
+*dp-- = 0;
+else
+*dp-- = 0xff;
+*dp-- = *sp--;
+*dp-- = *sp--;
+*dp-- = *sp--;
+}
+}
+else if (row_info->bit_depth == 16)
+{
+png_byte red_high = (png_byte)((trans_color->red >> 8) & 0xff);
+png_byte green_high = (png_byte)((trans_color->green >> 8) & 0xff);
+png_byte blue_high = (png_byte)((trans_color->blue >> 8) & 0xff);
+png_byte red_low = (png_byte)(trans_color->red & 0xff);
+png_byte green_low = (png_byte)(trans_color->green & 0xff);
+png_byte blue_low = (png_byte)(trans_color->blue & 0xff);
+sp = row + row_info->rowbytes - 1;
+dp = row + (png_size_t)(row_width << 3) - 1;
+for (i = 0; i < row_width; i++)
+{
+if (*(sp - 5) == red_high &&
+*(sp - 4) == red_low &&
+*(sp - 3) == green_high &&
+*(sp - 2) == green_low &&
+*(sp - 1) == blue_high &&
+*(sp    ) == blue_low)
+{
+*dp-- = 0;
+*dp-- = 0;
+}
+else
+{
+*dp-- = 0xff;
+*dp-- = 0xff;
+}
+*dp-- = *sp--;
+*dp-- = *sp--;
+*dp-- = *sp--;
+*dp-- = *sp--;
+*dp-- = *sp--;
+*dp-- = *sp--;
+}
+}
+row_info->color_type = PNG_COLOR_TYPE_RGB_ALPHA;
+row_info->channels = 4;
+row_info->pixel_depth = (png_byte)(row_info->bit_depth << 2);
+row_info->rowbytes = PNG_ROWBYTES(row_info->pixel_depth, row_width);
+}
+}
+}
+#endif
+#ifdef PNG_READ_EXPAND_16_SUPPORTED
+/* If the bit depth is 8 and the color type is not a palette type expand the
+* whole row to 16 bits.  Has no effect otherwise.
+*/
+static void
+png_do_expand_16(png_row_infop row_info, png_bytep row)
+{
+if (row_info->bit_depth == 8 &&
+row_info->color_type != PNG_COLOR_TYPE_PALETTE)
+{
+/* The row have a sequence of bytes containing [0..255] and we need
+* to turn it into another row containing [0..65535], to do this we
+* calculate:
+*
+*  (input / 255) * 65535
+*
+*  Which happens to be exactly input * 257 and this can be achieved
+*  simply by byte replication in place (copying backwards).
+*/
+png_byte *sp = row + row_info->rowbytes; /* source, last byte + 1 */
+png_byte *dp = sp + row_info->rowbytes;  /* destination, end + 1 */
+while (dp > sp)
+dp[-2] = dp[-1] = *--sp, dp -= 2;
+row_info->rowbytes *= 2;
+row_info->bit_depth = 16;
+row_info->pixel_depth = (png_byte)(row_info->channels * 16);
+}
+}
+#endif
+#ifdef PNG_READ_QUANTIZE_SUPPORTED
+static void
+png_do_quantize(png_row_infop row_info, png_bytep row,
+png_const_bytep palette_lookup, png_const_bytep quantize_lookup)
+{
+png_bytep sp, dp;
+png_uint_32 i;
+png_uint_32 row_width=row_info->width;
+png_debug(1, "in png_do_quantize");
+if (row_info->bit_depth == 8)
+{
+if (row_info->color_type == PNG_COLOR_TYPE_RGB && palette_lookup)
+{
+int r, g, b, p;
+sp = row;
+dp = row;
+for (i = 0; i < row_width; i++)
+{
+r = *sp++;
+g = *sp++;
+b = *sp++;
+/* This looks real messy, but the compiler will reduce
+* it down to a reasonable formula.  For example, with
+* 5 bits per color, we get:
+* p = (((r >> 3) & 0x1f) << 10) |
+*    (((g >> 3) & 0x1f) << 5) |
+*    ((b >> 3) & 0x1f);
+*/
+p = (((r >> (8 - PNG_QUANTIZE_RED_BITS)) &
+((1 << PNG_QUANTIZE_RED_BITS) - 1)) <<
+(PNG_QUANTIZE_GREEN_BITS + PNG_QUANTIZE_BLUE_BITS)) |
+(((g >> (8 - PNG_QUANTIZE_GREEN_BITS)) &
+((1 << PNG_QUANTIZE_GREEN_BITS) - 1)) <<
+(PNG_QUANTIZE_BLUE_BITS)) |
+((b >> (8 - PNG_QUANTIZE_BLUE_BITS)) &
+((1 << PNG_QUANTIZE_BLUE_BITS) - 1));
+*dp++ = palette_lookup[p];
+}
+row_info->color_type = PNG_COLOR_TYPE_PALETTE;
+row_info->channels = 1;
+row_info->pixel_depth = row_info->bit_depth;
+row_info->rowbytes = PNG_ROWBYTES(row_info->pixel_depth, row_width);
+}
+else if (row_info->color_type == PNG_COLOR_TYPE_RGB_ALPHA &&
+palette_lookup != NULL)
+{
+int r, g, b, p;
+sp = row;
+dp = row;
+for (i = 0; i < row_width; i++)
+{
+r = *sp++;
+g = *sp++;
+b = *sp++;
+sp++;
+p = (((r >> (8 - PNG_QUANTIZE_RED_BITS)) &
+((1 << PNG_QUANTIZE_RED_BITS) - 1)) <<
+(PNG_QUANTIZE_GREEN_BITS + PNG_QUANTIZE_BLUE_BITS)) |
+(((g >> (8 - PNG_QUANTIZE_GREEN_BITS)) &
+((1 << PNG_QUANTIZE_GREEN_BITS) - 1)) <<
+(PNG_QUANTIZE_BLUE_BITS)) |
+((b >> (8 - PNG_QUANTIZE_BLUE_BITS)) &
+((1 << PNG_QUANTIZE_BLUE_BITS) - 1));
+*dp++ = palette_lookup[p];
+}
+row_info->color_type = PNG_COLOR_TYPE_PALETTE;
+row_info->channels = 1;
+row_info->pixel_depth = row_info->bit_depth;
+row_info->rowbytes = PNG_ROWBYTES(row_info->pixel_depth, row_width);
+}
+else if (row_info->color_type == PNG_COLOR_TYPE_PALETTE &&
+quantize_lookup)
+{
+sp = row;
+for (i = 0; i < row_width; i++, sp++)
+{
+*sp = quantize_lookup[*sp];
+}
+}
+}
+}
+#endif /* PNG_READ_QUANTIZE_SUPPORTED */
+/* Transform the row.  The order of transformations is significant,
+* and is very touchy.  If you add a transformation, take care to
+* decide how it fits in with the other transformations here.
+*/
+void /* PRIVATE */
+png_do_read_transformations(png_structrp png_ptr, png_row_infop row_info)
+{
+png_debug(1, "in png_do_read_transformations");
+if (png_ptr->row_buf == NULL)
+{
+/* Prior to 1.5.4 this output row/pass where the NULL pointer is, but this
+* error is incredibly rare and incredibly easy to debug without this
+* information.
+*/
+png_error(png_ptr, "NULL row buffer");
+}
+/* The following is debugging; prior to 1.5.4 the code was never compiled in;
+* in 1.5.4 PNG_FLAG_DETECT_UNINITIALIZED was added and the macro
+* PNG_WARN_UNINITIALIZED_ROW removed.  In 1.6 the new flag is set only for
+* all transformations, however in practice the ROW_INIT always gets done on
+* demand, if necessary.
+*/
+if ((png_ptr->flags & PNG_FLAG_DETECT_UNINITIALIZED) != 0 &&
+!(png_ptr->flags & PNG_FLAG_ROW_INIT))
+{
+/* Application has failed to call either png_read_start_image() or
+* png_read_update_info() after setting transforms that expand pixels.
+* This check added to libpng-1.2.19 (but not enabled until 1.5.4).
+*/
+png_error(png_ptr, "Uninitialized row");
+}
+#ifdef PNG_READ_EXPAND_SUPPORTED
+if (png_ptr->transformations & PNG_EXPAND)
+{
+if (row_info->color_type == PNG_COLOR_TYPE_PALETTE)
+{
+png_do_expand_palette(row_info, png_ptr->row_buf + 1,
+png_ptr->palette, png_ptr->trans_alpha, png_ptr->num_trans);
+}
+else
+{
+if (png_ptr->num_trans &&
+(png_ptr->transformations & PNG_EXPAND_tRNS))
+png_do_expand(row_info, png_ptr->row_buf + 1,
+&(png_ptr->trans_color));
+else
+png_do_expand(row_info, png_ptr->row_buf + 1,
+NULL);
+}
+}
+#endif
+#ifdef PNG_READ_STRIP_ALPHA_SUPPORTED
+if ((png_ptr->transformations & PNG_STRIP_ALPHA) &&
+!(png_ptr->transformations & PNG_COMPOSE) &&
+(row_info->color_type == PNG_COLOR_TYPE_RGB_ALPHA ||
+row_info->color_type == PNG_COLOR_TYPE_GRAY_ALPHA))
+png_do_strip_channel(row_info, png_ptr->row_buf + 1,
+0 /* at_start == false, because SWAP_ALPHA happens later */);
+#endif
+#ifdef PNG_READ_RGB_TO_GRAY_SUPPORTED
+if (png_ptr->transformations & PNG_RGB_TO_GRAY)
+{
+int rgb_error =
+png_do_rgb_to_gray(png_ptr, row_info,
+png_ptr->row_buf + 1);
+if (rgb_error)
+{
+png_ptr->rgb_to_gray_status=1;
+if ((png_ptr->transformations & PNG_RGB_TO_GRAY) ==
+PNG_RGB_TO_GRAY_WARN)
+png_warning(png_ptr, "png_do_rgb_to_gray found nongray pixel");
+if ((png_ptr->transformations & PNG_RGB_TO_GRAY) ==
+PNG_RGB_TO_GRAY_ERR)
+png_error(png_ptr, "png_do_rgb_to_gray found nongray pixel");
+}
+}
+#endif
+/* From Andreas Dilger e-mail to png-implement, 26 March 1998:
+*
+*   In most cases, the "simple transparency" should be done prior to doing
+*   gray-to-RGB, or you will have to test 3x as many bytes to check if a
+*   pixel is transparent.  You would also need to make sure that the
+*   transparency information is upgraded to RGB.
+*
+*   To summarize, the current flow is:
+*   - Gray + simple transparency -> compare 1 or 2 gray bytes and composite
+*                                   with background "in place" if transparent,
+*                                   convert to RGB if necessary
+*   - Gray + alpha -> composite with gray background and remove alpha bytes,
+*                                   convert to RGB if necessary
+*
+*   To support RGB backgrounds for gray images we need:
+*   - Gray + simple transparency -> convert to RGB + simple transparency,
+*                                   compare 3 or 6 bytes and composite with
+*                                   background "in place" if transparent
+*                                   (3x compare/pixel compared to doing
+*                                   composite with gray bkgrnd)
+*   - Gray + alpha -> convert to RGB + alpha, composite with background and
+*                                   remove alpha bytes (3x float
+*                                   operations/pixel compared with composite
+*                                   on gray background)
+*
+*  Greg's change will do this.  The reason it wasn't done before is for
+*  performance, as this increases the per-pixel operations.  If we would check
+*  in advance if the background was gray or RGB, and position the gray-to-RGB
+*  transform appropriately, then it would save a lot of work/time.
+*/
+#ifdef PNG_READ_GRAY_TO_RGB_SUPPORTED
+/* If gray -> RGB, do so now only if background is non-gray; else do later
+* for performance reasons
+*/
+if ((png_ptr->transformations & PNG_GRAY_TO_RGB) &&
+!(png_ptr->mode & PNG_BACKGROUND_IS_GRAY))
+png_do_gray_to_rgb(row_info, png_ptr->row_buf + 1);
+#endif
+#if defined(PNG_READ_BACKGROUND_SUPPORTED) ||\
+defined(PNG_READ_ALPHA_MODE_SUPPORTED)
+if (png_ptr->transformations & PNG_COMPOSE)
+png_do_compose(row_info, png_ptr->row_buf + 1, png_ptr);
+#endif
+#ifdef PNG_READ_GAMMA_SUPPORTED
+if ((png_ptr->transformations & PNG_GAMMA) &&
+#ifdef PNG_READ_RGB_TO_GRAY_SUPPORTED
+/* Because RGB_TO_GRAY does the gamma transform. */
+!(png_ptr->transformations & PNG_RGB_TO_GRAY) &&
+#endif
+#if defined(PNG_READ_BACKGROUND_SUPPORTED) ||\
+defined(PNG_READ_ALPHA_MODE_SUPPORTED)
+/* Because PNG_COMPOSE does the gamma transform if there is something to
+* do (if there is an alpha channel or transparency.)
+*/
+!((png_ptr->transformations & PNG_COMPOSE) &&
+((png_ptr->num_trans != 0) ||
+(png_ptr->color_type & PNG_COLOR_MASK_ALPHA))) &&
+#endif
+/* Because png_init_read_transformations transforms the palette, unless
+* RGB_TO_GRAY will do the transform.
+*/
+(png_ptr->color_type != PNG_COLOR_TYPE_PALETTE))
+png_do_gamma(row_info, png_ptr->row_buf + 1, png_ptr);
+#endif
+#ifdef PNG_READ_STRIP_ALPHA_SUPPORTED
+if ((png_ptr->transformations & PNG_STRIP_ALPHA) &&
+(png_ptr->transformations & PNG_COMPOSE) &&
+(row_info->color_type == PNG_COLOR_TYPE_RGB_ALPHA ||
+row_info->color_type == PNG_COLOR_TYPE_GRAY_ALPHA))
+png_do_strip_channel(row_info, png_ptr->row_buf + 1,
+0 /* at_start == false, because SWAP_ALPHA happens later */);
+#endif
+#ifdef PNG_READ_ALPHA_MODE_SUPPORTED
+if ((png_ptr->transformations & PNG_ENCODE_ALPHA) &&
+(row_info->color_type & PNG_COLOR_MASK_ALPHA))
+png_do_encode_alpha(row_info, png_ptr->row_buf + 1, png_ptr);
+#endif
+#ifdef PNG_READ_SCALE_16_TO_8_SUPPORTED
+if (png_ptr->transformations & PNG_SCALE_16_TO_8)
+png_do_scale_16_to_8(row_info, png_ptr->row_buf + 1);
+#endif
+#ifdef PNG_READ_STRIP_16_TO_8_SUPPORTED
+/* There is no harm in doing both of these because only one has any effect,
+* by putting the 'scale' option first if the app asks for scale (either by
+* calling the API or in a TRANSFORM flag) this is what happens.
+*/
+if (png_ptr->transformations & PNG_16_TO_8)
+png_do_chop(row_info, png_ptr->row_buf + 1);
+#endif
+#ifdef PNG_READ_QUANTIZE_SUPPORTED
+if (png_ptr->transformations & PNG_QUANTIZE)
+{
+png_do_quantize(row_info, png_ptr->row_buf + 1,
+png_ptr->palette_lookup, png_ptr->quantize_index);
+if (row_info->rowbytes == 0)
+png_error(png_ptr, "png_do_quantize returned rowbytes=0");
+}
+#endif /* PNG_READ_QUANTIZE_SUPPORTED */
+#ifdef PNG_READ_EXPAND_16_SUPPORTED
+/* Do the expansion now, after all the arithmetic has been done.  Notice
+* that previous transformations can handle the PNG_EXPAND_16 flag if this
+* is efficient (particularly true in the case of gamma correction, where
+* better accuracy results faster!)
+*/
+if (png_ptr->transformations & PNG_EXPAND_16)
+png_do_expand_16(row_info, png_ptr->row_buf + 1);
+#endif
+#ifdef PNG_READ_GRAY_TO_RGB_SUPPORTED
+/* NOTE: moved here in 1.5.4 (from much later in this list.) */
+if ((png_ptr->transformations & PNG_GRAY_TO_RGB) &&
+(png_ptr->mode & PNG_BACKGROUND_IS_GRAY))
+png_do_gray_to_rgb(row_info, png_ptr->row_buf + 1);
+#endif
+#ifdef PNG_READ_INVERT_SUPPORTED
+if (png_ptr->transformations & PNG_INVERT_MONO)
+png_do_invert(row_info, png_ptr->row_buf + 1);
+#endif
+#ifdef PNG_READ_INVERT_ALPHA_SUPPORTED
+if (png_ptr->transformations & PNG_INVERT_ALPHA)
+png_do_read_invert_alpha(row_info, png_ptr->row_buf + 1);
+#endif
+#ifdef PNG_READ_SHIFT_SUPPORTED
+if (png_ptr->transformations & PNG_SHIFT)
+png_do_unshift(row_info, png_ptr->row_buf + 1,
+&(png_ptr->shift));
+#endif
+#ifdef PNG_READ_PACK_SUPPORTED
+if (png_ptr->transformations & PNG_PACK)
+png_do_unpack(row_info, png_ptr->row_buf + 1);
+#endif
+#ifdef PNG_READ_CHECK_FOR_INVALID_INDEX_SUPPORTED
+/* Added at libpng-1.5.10 */
+if (row_info->color_type == PNG_COLOR_TYPE_PALETTE &&
+png_ptr->num_palette_max >= 0)
+png_do_check_palette_indexes(png_ptr, row_info);
+#endif
+#ifdef PNG_READ_BGR_SUPPORTED
+if (png_ptr->transformations & PNG_BGR)
+png_do_bgr(row_info, png_ptr->row_buf + 1);
+#endif
+#ifdef PNG_READ_PACKSWAP_SUPPORTED
+if (png_ptr->transformations & PNG_PACKSWAP)
+png_do_packswap(row_info, png_ptr->row_buf + 1);
+#endif
+#ifdef PNG_READ_FILLER_SUPPORTED
+if (png_ptr->transformations & PNG_FILLER)
+png_do_read_filler(row_info, png_ptr->row_buf + 1,
+(png_uint_32)png_ptr->filler, png_ptr->flags);
+#endif
+#ifdef PNG_READ_SWAP_ALPHA_SUPPORTED
+if (png_ptr->transformations & PNG_SWAP_ALPHA)
+png_do_read_swap_alpha(row_info, png_ptr->row_buf + 1);
+#endif
+#ifdef PNG_READ_16BIT_SUPPORTED
+#ifdef PNG_READ_SWAP_SUPPORTED
+if (png_ptr->transformations & PNG_SWAP_BYTES)
+png_do_swap(row_info, png_ptr->row_buf + 1);
+#endif
+#endif
+#ifdef PNG_READ_USER_TRANSFORM_SUPPORTED
+if (png_ptr->transformations & PNG_USER_TRANSFORM)
+{
+if (png_ptr->read_user_transform_fn != NULL)
+(*(png_ptr->read_user_transform_fn)) /* User read transform function */
+(png_ptr,     /* png_ptr */
+row_info,     /* row_info: */
+/*  png_uint_32 width;       width of row */
+/*  png_size_t rowbytes;     number of bytes in row */
+/*  png_byte color_type;     color type of pixels */
+/*  png_byte bit_depth;      bit depth of samples */
+/*  png_byte channels;       number of channels (1-4) */
+/*  png_byte pixel_depth;    bits per pixel (depth*channels) */
+png_ptr->row_buf + 1);    /* start of pixel data for row */
+#ifdef PNG_USER_TRANSFORM_PTR_SUPPORTED
+if (png_ptr->user_transform_depth)
+row_info->bit_depth = png_ptr->user_transform_depth;
+if (png_ptr->user_transform_channels)
+row_info->channels = png_ptr->user_transform_channels;
+#endif
+row_info->pixel_depth = (png_byte)(row_info->bit_depth *
+row_info->channels);
+row_info->rowbytes = PNG_ROWBYTES(row_info->pixel_depth, row_info->width);
+}
+#endif
+}
+#endif /* PNG_READ_TRANSFORMS_SUPPORTED */
+#endif /* PNG_READ_SUPPORTED */

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