The Tor Browser: media/libjpeg/jquant1.c@b8a032363ba2 (annotated)

media/libjpeg/jquant1.c@b8a032363ba2 (annotated)

media/libjpeg/jquant1.c

Thu, 22 Jan 2015 13:21:57 +0100

author: Michael Schloh von Bennewitz <michael@schloh.com>
date: Thu, 22 Jan 2015 13:21:57 +0100
branch: TOR_BUG_9701
changeset 15: b8a032363ba2
permissions: -rw-r--r--

Incorporate requested changes from Mozilla in review:
https://bugzilla.mozilla.org/show_bug.cgi?id=1123480#c6

 /*
  * jquant1.c
  *
  * This file was part of the Independent JPEG Group's software:
  * Copyright (C) 1991-1996, Thomas G. Lane.
  * libjpeg-turbo Modifications:
  * Copyright (C) 2009, D. R. Commander
  * For conditions of distribution and use, see the accompanying README file.
  *
  * This file contains 1-pass color quantization (color mapping) routines.
  * These routines provide mapping to a fixed color map using equally spaced
  * color values.  Optional Floyd-Steinberg or ordered dithering is available.
  */
 #define JPEG_INTERNALS
 #include "jinclude.h"
 #include "jpeglib.h"
 #ifdef QUANT_1PASS_SUPPORTED
 /*
  * The main purpose of 1-pass quantization is to provide a fast, if not very
  * high quality, colormapped output capability.  A 2-pass quantizer usually
  * gives better visual quality; however, for quantized grayscale output this
  * quantizer is perfectly adequate.  Dithering is highly recommended with this
  * quantizer, though you can turn it off if you really want to.
  *
  * In 1-pass quantization the colormap must be chosen in advance of seeing the
  * image.  We use a map consisting of all combinations of Ncolors[i] color
  * values for the i'th component.  The Ncolors[] values are chosen so that
  * their product, the total number of colors, is no more than that requested.
  * (In most cases, the product will be somewhat less.)
  *
  * Since the colormap is orthogonal, the representative value for each color
  * component can be determined without considering the other components;
  * then these indexes can be combined into a colormap index by a standard
  * N-dimensional-array-subscript calculation.  Most of the arithmetic involved
  * can be precalculated and stored in the lookup table colorindex[].
  * colorindex[i][j] maps pixel value j in component i to the nearest
  * representative value (grid plane) for that component; this index is
  * multiplied by the array stride for component i, so that the
  * index of the colormap entry closest to a given pixel value is just
  *    sum( colorindex[component-number][pixel-component-value] )
  * Aside from being fast, this scheme allows for variable spacing between
  * representative values with no additional lookup cost.
  *
  * If gamma correction has been applied in color conversion, it might be wise
  * to adjust the color grid spacing so that the representative colors are
  * equidistant in linear space.  At this writing, gamma correction is not
  * implemented by jdcolor, so nothing is done here.
  */
 /* Declarations for ordered dithering.
  *
  * We use a standard 16x16 ordered dither array.  The basic concept of ordered
  * dithering is described in many references, for instance Dale Schumacher's
  * chapter II.2 of Graphics Gems II (James Arvo, ed. Academic Press, 1991).
  * In place of Schumacher's comparisons against a "threshold" value, we add a
  * "dither" value to the input pixel and then round the result to the nearest
  * output value.  The dither value is equivalent to (0.5 - threshold) times
  * the distance between output values.  For ordered dithering, we assume that
  * the output colors are equally spaced; if not, results will probably be
  * worse, since the dither may be too much or too little at a given point.
  *
  * The normal calculation would be to form pixel value + dither, range-limit
  * this to 0..MAXJSAMPLE, and then index into the colorindex table as usual.
  * We can skip the separate range-limiting step by extending the colorindex
  * table in both directions.
  */
 #define ODITHER_SIZE  16	/* dimension of dither matrix */
 /* NB: if ODITHER_SIZE is not a power of 2, ODITHER_MASK uses will break */
 #define ODITHER_CELLS (ODITHER_SIZE*ODITHER_SIZE)	/* # cells in matrix */
 #define ODITHER_MASK  (ODITHER_SIZE-1) /* mask for wrapping around counters */
 typedef int ODITHER_MATRIX[ODITHER_SIZE][ODITHER_SIZE];
 typedef int (*ODITHER_MATRIX_PTR)[ODITHER_SIZE];
 static const UINT8 base_dither_matrix[ODITHER_SIZE][ODITHER_SIZE] = {
   /* Bayer's order-4 dither array.  Generated by the code given in
    * Stephen Hawley's article "Ordered Dithering" in Graphics Gems I.
    * The values in this array must range from 0 to ODITHER_CELLS-1.
    */
   {   0,192, 48,240, 12,204, 60,252,  3,195, 51,243, 15,207, 63,255 },
   { 128, 64,176,112,140, 76,188,124,131, 67,179,115,143, 79,191,127 },
   {  32,224, 16,208, 44,236, 28,220, 35,227, 19,211, 47,239, 31,223 },
   { 160, 96,144, 80,172,108,156, 92,163, 99,147, 83,175,111,159, 95 },
   {   8,200, 56,248,  4,196, 52,244, 11,203, 59,251,  7,199, 55,247 },
   { 136, 72,184,120,132, 68,180,116,139, 75,187,123,135, 71,183,119 },
   {  40,232, 24,216, 36,228, 20,212, 43,235, 27,219, 39,231, 23,215 },
   { 168,104,152, 88,164,100,148, 84,171,107,155, 91,167,103,151, 87 },
   {   2,194, 50,242, 14,206, 62,254,  1,193, 49,241, 13,205, 61,253 },
   { 130, 66,178,114,142, 78,190,126,129, 65,177,113,141, 77,189,125 },
   {  34,226, 18,210, 46,238, 30,222, 33,225, 17,209, 45,237, 29,221 },
   { 162, 98,146, 82,174,110,158, 94,161, 97,145, 81,173,109,157, 93 },
   {  10,202, 58,250,  6,198, 54,246,  9,201, 57,249,  5,197, 53,245 },
   { 138, 74,186,122,134, 70,182,118,137, 73,185,121,133, 69,181,117 },
   {  42,234, 26,218, 38,230, 22,214, 41,233, 25,217, 37,229, 21,213 },
   { 170,106,154, 90,166,102,150, 86,169,105,153, 89,165,101,149, 85 }
 };
 /* Declarations for Floyd-Steinberg dithering.
  *
  * Errors are accumulated into the array fserrors[], at a resolution of
  * 1/16th of a pixel count.  The error at a given pixel is propagated
  * to its not-yet-processed neighbors using the standard F-S fractions,
  *		...	(here)	7/16
  *		3/16	5/16	1/16
  * We work left-to-right on even rows, right-to-left on odd rows.
  *
  * We can get away with a single array (holding one row's worth of errors)
  * by using it to store the current row's errors at pixel columns not yet
  * processed, but the next row's errors at columns already processed.  We
  * need only a few extra variables to hold the errors immediately around the
  * current column.  (If we are lucky, those variables are in registers, but
  * even if not, they're probably cheaper to access than array elements are.)
  *
  * The fserrors[] array is indexed [component#][position].
  * We provide (#columns + 2) entries per component; the extra entry at each
  * end saves us from special-casing the first and last pixels.
  *
  * Note: on a wide image, we might not have enough room in a PC's near data
  * segment to hold the error array; so it is allocated with alloc_large.
  */
 #if BITS_IN_JSAMPLE == 8
 typedef INT16 FSERROR;		/* 16 bits should be enough */
 typedef int LOCFSERROR;		/* use 'int' for calculation temps */
 #else
 typedef INT32 FSERROR;		/* may need more than 16 bits */
 typedef INT32 LOCFSERROR;	/* be sure calculation temps are big enough */
 #endif
 typedef FSERROR FAR *FSERRPTR;	/* pointer to error array (in FAR storage!) */
 /* Private subobject */
 #define MAX_Q_COMPS 4		/* max components I can handle */
 typedef struct {
   struct jpeg_color_quantizer pub; /* public fields */
   /* Initially allocated colormap is saved here */
   JSAMPARRAY sv_colormap;	/* The color map as a 2-D pixel array */
   int sv_actual;		/* number of entries in use */
   JSAMPARRAY colorindex;	/* Precomputed mapping for speed */
   /* colorindex[i][j] = index of color closest to pixel value j in component i,
    * premultiplied as described above.  Since colormap indexes must fit into
    * JSAMPLEs, the entries of this array will too.
    */
   boolean is_padded;		/* is the colorindex padded for odither? */
   int Ncolors[MAX_Q_COMPS];	/* # of values alloced to each component */
   /* Variables for ordered dithering */
   int row_index;		/* cur row's vertical index in dither matrix */
   ODITHER_MATRIX_PTR odither[MAX_Q_COMPS]; /* one dither array per component */
   /* Variables for Floyd-Steinberg dithering */
   FSERRPTR fserrors[MAX_Q_COMPS]; /* accumulated errors */
   boolean on_odd_row;		/* flag to remember which row we are on */
 } my_cquantizer;
 typedef my_cquantizer * my_cquantize_ptr;
 /*
  * Policy-making subroutines for create_colormap and create_colorindex.
  * These routines determine the colormap to be used.  The rest of the module
  * only assumes that the colormap is orthogonal.
  *
  *  * select_ncolors decides how to divvy up the available colors
  *    among the components.
  *  * output_value defines the set of representative values for a component.
  *  * largest_input_value defines the mapping from input values to
  *    representative values for a component.
  * Note that the latter two routines may impose different policies for
  * different components, though this is not currently done.
  */
 LOCAL(int)
 select_ncolors (j_decompress_ptr cinfo, int Ncolors[])
 /* Determine allocation of desired colors to components, */
 /* and fill in Ncolors[] array to indicate choice. */
 /* Return value is total number of colors (product of Ncolors[] values). */
 {
   int nc = cinfo->out_color_components; /* number of color components */
   int max_colors = cinfo->desired_number_of_colors;
   int total_colors, iroot, i, j;
   boolean changed;
   long temp;
   int RGB_order[3] = { RGB_GREEN, RGB_RED, RGB_BLUE };
   RGB_order[0] = rgb_green[cinfo->out_color_space];
   RGB_order[1] = rgb_red[cinfo->out_color_space];
   RGB_order[2] = rgb_blue[cinfo->out_color_space];
   /* We can allocate at least the nc'th root of max_colors per component. */
   /* Compute floor(nc'th root of max_colors). */
   iroot = 1;
   do {
     iroot++;
     temp = iroot;		/* set temp = iroot ** nc */
     for (i = 1; i < nc; i++)
       temp *= iroot;
   } while (temp <= (long) max_colors); /* repeat till iroot exceeds root */
   iroot--;			/* now iroot = floor(root) */
   /* Must have at least 2 color values per component */
   if (iroot < 2)
     ERREXIT1(cinfo, JERR_QUANT_FEW_COLORS, (int) temp);
   /* Initialize to iroot color values for each component */
   total_colors = 1;
   for (i = 0; i < nc; i++) {
     Ncolors[i] = iroot;
     total_colors *= iroot;
   }
   /* We may be able to increment the count for one or more components without
    * exceeding max_colors, though we know not all can be incremented.
    * Sometimes, the first component can be incremented more than once!
    * (Example: for 16 colors, we start at 2*2*2, go to 3*2*2, then 4*2*2.)
    * In RGB colorspace, try to increment G first, then R, then B.
    */
   do {
     changed = FALSE;
     for (i = 0; i < nc; i++) {
       j = (cinfo->out_color_space == JCS_RGB ? RGB_order[i] : i);
       /* calculate new total_colors if Ncolors[j] is incremented */
       temp = total_colors / Ncolors[j];
       temp *= Ncolors[j]+1;	/* done in long arith to avoid oflo */
       if (temp > (long) max_colors)
 	break;			/* won't fit, done with this pass */
       Ncolors[j]++;		/* OK, apply the increment */
       total_colors = (int) temp;
       changed = TRUE;
     }
   } while (changed);
   return total_colors;
 }
 LOCAL(int)
 output_value (j_decompress_ptr cinfo, int ci, int j, int maxj)
 /* Return j'th output value, where j will range from 0 to maxj */
 /* The output values must fall in 0..MAXJSAMPLE in increasing order */
 {
   /* We always provide values 0 and MAXJSAMPLE for each component;
    * any additional values are equally spaced between these limits.
    * (Forcing the upper and lower values to the limits ensures that
    * dithering can't produce a color outside the selected gamut.)
    */
   return (int) (((INT32) j * MAXJSAMPLE + maxj/2) / maxj);
 }
 LOCAL(int)
 largest_input_value (j_decompress_ptr cinfo, int ci, int j, int maxj)
 /* Return largest input value that should map to j'th output value */
 /* Must have largest(j=0) >= 0, and largest(j=maxj) >= MAXJSAMPLE */
 {
   /* Breakpoints are halfway between values returned by output_value */
   return (int) (((INT32) (2*j + 1) * MAXJSAMPLE + maxj) / (2*maxj));
 }
 /*
  * Create the colormap.
  */
 LOCAL(void)
 create_colormap (j_decompress_ptr cinfo)
 {
   my_cquantize_ptr cquantize = (my_cquantize_ptr) cinfo->cquantize;
   JSAMPARRAY colormap;		/* Created colormap */
   int total_colors;		/* Number of distinct output colors */
   int i,j,k, nci, blksize, blkdist, ptr, val;
   /* Select number of colors for each component */
   total_colors = select_ncolors(cinfo, cquantize->Ncolors);
   /* Report selected color counts */
   if (cinfo->out_color_components == 3)
     TRACEMS4(cinfo, 1, JTRC_QUANT_3_NCOLORS,
 	     total_colors, cquantize->Ncolors[0],
 	     cquantize->Ncolors[1], cquantize->Ncolors[2]);
   else
     TRACEMS1(cinfo, 1, JTRC_QUANT_NCOLORS, total_colors);
   /* Allocate and fill in the colormap. */
   /* The colors are ordered in the map in standard row-major order, */
   /* i.e. rightmost (highest-indexed) color changes most rapidly. */
   colormap = (*cinfo->mem->alloc_sarray)
     ((j_common_ptr) cinfo, JPOOL_IMAGE,
      (JDIMENSION) total_colors, (JDIMENSION) cinfo->out_color_components);
   /* blksize is number of adjacent repeated entries for a component */
   /* blkdist is distance between groups of identical entries for a component */
   blkdist = total_colors;
   for (i = 0; i < cinfo->out_color_components; i++) {
     /* fill in colormap entries for i'th color component */
     nci = cquantize->Ncolors[i]; /* # of distinct values for this color */
     blksize = blkdist / nci;
     for (j = 0; j < nci; j++) {
       /* Compute j'th output value (out of nci) for component */
       val = output_value(cinfo, i, j, nci-1);
       /* Fill in all colormap entries that have this value of this component */
       for (ptr = j * blksize; ptr < total_colors; ptr += blkdist) {
 	/* fill in blksize entries beginning at ptr */
 	for (k = 0; k < blksize; k++)
 	  colormap[i][ptr+k] = (JSAMPLE) val;
       }
     }
     blkdist = blksize;		/* blksize of this color is blkdist of next */
   }
   /* Save the colormap in private storage,
    * where it will survive color quantization mode changes.
    */
   cquantize->sv_colormap = colormap;
   cquantize->sv_actual = total_colors;
 }
 /*
  * Create the color index table.
  */
 LOCAL(void)
 create_colorindex (j_decompress_ptr cinfo)
 {
   my_cquantize_ptr cquantize = (my_cquantize_ptr) cinfo->cquantize;
   JSAMPROW indexptr;
   int i,j,k, nci, blksize, val, pad;
   /* For ordered dither, we pad the color index tables by MAXJSAMPLE in
    * each direction (input index values can be -MAXJSAMPLE .. 2*MAXJSAMPLE).
    * This is not necessary in the other dithering modes.  However, we
    * flag whether it was done in case user changes dithering mode.
    */
   if (cinfo->dither_mode == JDITHER_ORDERED) {
     pad = MAXJSAMPLE*2;
     cquantize->is_padded = TRUE;
   } else {
     pad = 0;
     cquantize->is_padded = FALSE;
   }
   cquantize->colorindex = (*cinfo->mem->alloc_sarray)
     ((j_common_ptr) cinfo, JPOOL_IMAGE,
      (JDIMENSION) (MAXJSAMPLE+1 + pad),
      (JDIMENSION) cinfo->out_color_components);
   /* blksize is number of adjacent repeated entries for a component */
   blksize = cquantize->sv_actual;
   for (i = 0; i < cinfo->out_color_components; i++) {
     /* fill in colorindex entries for i'th color component */
     nci = cquantize->Ncolors[i]; /* # of distinct values for this color */
     blksize = blksize / nci;
     /* adjust colorindex pointers to provide padding at negative indexes. */
     if (pad)
       cquantize->colorindex[i] += MAXJSAMPLE;
     /* in loop, val = index of current output value, */
     /* and k = largest j that maps to current val */
     indexptr = cquantize->colorindex[i];
     val = 0;
     k = largest_input_value(cinfo, i, 0, nci-1);
     for (j = 0; j <= MAXJSAMPLE; j++) {
       while (j > k)		/* advance val if past boundary */
 	k = largest_input_value(cinfo, i, ++val, nci-1);
       /* premultiply so that no multiplication needed in main processing */
       indexptr[j] = (JSAMPLE) (val * blksize);
     }
     /* Pad at both ends if necessary */
     if (pad)
       for (j = 1; j <= MAXJSAMPLE; j++) {
 	indexptr[-j] = indexptr[0];
 	indexptr[MAXJSAMPLE+j] = indexptr[MAXJSAMPLE];
       }
   }
 }
 /*
  * Create an ordered-dither array for a component having ncolors
  * distinct output values.
  */
 LOCAL(ODITHER_MATRIX_PTR)
 make_odither_array (j_decompress_ptr cinfo, int ncolors)
 {
   ODITHER_MATRIX_PTR odither;
   int j,k;
   INT32 num,den;
   odither = (ODITHER_MATRIX_PTR)
     (*cinfo->mem->alloc_small) ((j_common_ptr) cinfo, JPOOL_IMAGE,
 				SIZEOF(ODITHER_MATRIX));
   /* The inter-value distance for this color is MAXJSAMPLE/(ncolors-1).
    * Hence the dither value for the matrix cell with fill order f
    * (f=0..N-1) should be (N-1-2*f)/(2*N) * MAXJSAMPLE/(ncolors-1).
    * On 16-bit-int machine, be careful to avoid overflow.
    */
   den = 2 * ODITHER_CELLS * ((INT32) (ncolors - 1));
   for (j = 0; j < ODITHER_SIZE; j++) {
     for (k = 0; k < ODITHER_SIZE; k++) {
       num = ((INT32) (ODITHER_CELLS-1 - 2*((int)base_dither_matrix[j][k])))
 	    * MAXJSAMPLE;
       /* Ensure round towards zero despite C's lack of consistency
        * about rounding negative values in integer division...
        */
       odither[j][k] = (int) (num<0 ? -((-num)/den) : num/den);
     }
   }
   return odither;
 }
 /*
  * Create the ordered-dither tables.
  * Components having the same number of representative colors may
  * share a dither table.
  */
 LOCAL(void)
 create_odither_tables (j_decompress_ptr cinfo)
 {
   my_cquantize_ptr cquantize = (my_cquantize_ptr) cinfo->cquantize;
   ODITHER_MATRIX_PTR odither;
   int i, j, nci;
   for (i = 0; i < cinfo->out_color_components; i++) {
     nci = cquantize->Ncolors[i]; /* # of distinct values for this color */
     odither = NULL;		/* search for matching prior component */
     for (j = 0; j < i; j++) {
       if (nci == cquantize->Ncolors[j]) {
 	odither = cquantize->odither[j];
 	break;
       }
     }
     if (odither == NULL)	/* need a new table? */
       odither = make_odither_array(cinfo, nci);
     cquantize->odither[i] = odither;
   }
 }
 /*
  * Map some rows of pixels to the output colormapped representation.
  */
 METHODDEF(void)
 color_quantize (j_decompress_ptr cinfo, JSAMPARRAY input_buf,
 		JSAMPARRAY output_buf, int num_rows)
 /* General case, no dithering */
 {
   my_cquantize_ptr cquantize = (my_cquantize_ptr) cinfo->cquantize;
   JSAMPARRAY colorindex = cquantize->colorindex;
   register int pixcode, ci;
   register JSAMPROW ptrin, ptrout;
   int row;
   JDIMENSION col;
   JDIMENSION width = cinfo->output_width;
   register int nc = cinfo->out_color_components;
   for (row = 0; row < num_rows; row++) {
     ptrin = input_buf[row];
     ptrout = output_buf[row];
     for (col = width; col > 0; col--) {
       pixcode = 0;
       for (ci = 0; ci < nc; ci++) {
 	pixcode += GETJSAMPLE(colorindex[ci][GETJSAMPLE(*ptrin++)]);
       }
       *ptrout++ = (JSAMPLE) pixcode;
     }
   }
 }
 METHODDEF(void)
 color_quantize3 (j_decompress_ptr cinfo, JSAMPARRAY input_buf,
 		 JSAMPARRAY output_buf, int num_rows)
 /* Fast path for out_color_components==3, no dithering */
 {
   my_cquantize_ptr cquantize = (my_cquantize_ptr) cinfo->cquantize;
   register int pixcode;
   register JSAMPROW ptrin, ptrout;
   JSAMPROW colorindex0 = cquantize->colorindex[0];
   JSAMPROW colorindex1 = cquantize->colorindex[1];
   JSAMPROW colorindex2 = cquantize->colorindex[2];
   int row;
   JDIMENSION col;
   JDIMENSION width = cinfo->output_width;
   for (row = 0; row < num_rows; row++) {
     ptrin = input_buf[row];
     ptrout = output_buf[row];
     for (col = width; col > 0; col--) {
       pixcode  = GETJSAMPLE(colorindex0[GETJSAMPLE(*ptrin++)]);
       pixcode += GETJSAMPLE(colorindex1[GETJSAMPLE(*ptrin++)]);
       pixcode += GETJSAMPLE(colorindex2[GETJSAMPLE(*ptrin++)]);
       *ptrout++ = (JSAMPLE) pixcode;
     }
   }
 }
 METHODDEF(void)
 quantize_ord_dither (j_decompress_ptr cinfo, JSAMPARRAY input_buf,
 		     JSAMPARRAY output_buf, int num_rows)
 /* General case, with ordered dithering */
 {
   my_cquantize_ptr cquantize = (my_cquantize_ptr) cinfo->cquantize;
   register JSAMPROW input_ptr;
   register JSAMPROW output_ptr;
   JSAMPROW colorindex_ci;
   int * dither;			/* points to active row of dither matrix */
   int row_index, col_index;	/* current indexes into dither matrix */
   int nc = cinfo->out_color_components;
   int ci;
   int row;
   JDIMENSION col;
   JDIMENSION width = cinfo->output_width;
   for (row = 0; row < num_rows; row++) {
     /* Initialize output values to 0 so can process components separately */
     jzero_far((void FAR *) output_buf[row],
 	      (size_t) (width * SIZEOF(JSAMPLE)));
     row_index = cquantize->row_index;
     for (ci = 0; ci < nc; ci++) {
       input_ptr = input_buf[row] + ci;
       output_ptr = output_buf[row];
       colorindex_ci = cquantize->colorindex[ci];
       dither = cquantize->odither[ci][row_index];
       col_index = 0;
       for (col = width; col > 0; col--) {
 	/* Form pixel value + dither, range-limit to 0..MAXJSAMPLE,
 	 * select output value, accumulate into output code for this pixel.
 	 * Range-limiting need not be done explicitly, as we have extended
 	 * the colorindex table to produce the right answers for out-of-range
 	 * inputs.  The maximum dither is +- MAXJSAMPLE; this sets the
 	 * required amount of padding.
 	 */
 	*output_ptr += colorindex_ci[GETJSAMPLE(*input_ptr)+dither[col_index]];
 	input_ptr += nc;
 	output_ptr++;
 	col_index = (col_index + 1) & ODITHER_MASK;
       }
     }
     /* Advance row index for next row */
     row_index = (row_index + 1) & ODITHER_MASK;
     cquantize->row_index = row_index;
   }
 }
 METHODDEF(void)
 quantize3_ord_dither (j_decompress_ptr cinfo, JSAMPARRAY input_buf,
 		      JSAMPARRAY output_buf, int num_rows)
 /* Fast path for out_color_components==3, with ordered dithering */
 {
   my_cquantize_ptr cquantize = (my_cquantize_ptr) cinfo->cquantize;
   register int pixcode;
   register JSAMPROW input_ptr;
   register JSAMPROW output_ptr;
   JSAMPROW colorindex0 = cquantize->colorindex[0];
   JSAMPROW colorindex1 = cquantize->colorindex[1];
   JSAMPROW colorindex2 = cquantize->colorindex[2];
   int * dither0;		/* points to active row of dither matrix */
   int * dither1;
   int * dither2;
   int row_index, col_index;	/* current indexes into dither matrix */
   int row;
   JDIMENSION col;
   JDIMENSION width = cinfo->output_width;
   for (row = 0; row < num_rows; row++) {
     row_index = cquantize->row_index;
     input_ptr = input_buf[row];
     output_ptr = output_buf[row];
     dither0 = cquantize->odither[0][row_index];
     dither1 = cquantize->odither[1][row_index];
     dither2 = cquantize->odither[2][row_index];
     col_index = 0;
     for (col = width; col > 0; col--) {
       pixcode  = GETJSAMPLE(colorindex0[GETJSAMPLE(*input_ptr++) +
 					dither0[col_index]]);
       pixcode += GETJSAMPLE(colorindex1[GETJSAMPLE(*input_ptr++) +
 					dither1[col_index]]);
       pixcode += GETJSAMPLE(colorindex2[GETJSAMPLE(*input_ptr++) +
 					dither2[col_index]]);
       *output_ptr++ = (JSAMPLE) pixcode;
       col_index = (col_index + 1) & ODITHER_MASK;
     }
     row_index = (row_index + 1) & ODITHER_MASK;
     cquantize->row_index = row_index;
   }
 }
 METHODDEF(void)
 quantize_fs_dither (j_decompress_ptr cinfo, JSAMPARRAY input_buf,
 		    JSAMPARRAY output_buf, int num_rows)
 /* General case, with Floyd-Steinberg dithering */
 {
   my_cquantize_ptr cquantize = (my_cquantize_ptr) cinfo->cquantize;
   register LOCFSERROR cur;	/* current error or pixel value */
   LOCFSERROR belowerr;		/* error for pixel below cur */
   LOCFSERROR bpreverr;		/* error for below/prev col */
   LOCFSERROR bnexterr;		/* error for below/next col */
   LOCFSERROR delta;
   register FSERRPTR errorptr;	/* => fserrors[] at column before current */
   register JSAMPROW input_ptr;
   register JSAMPROW output_ptr;
   JSAMPROW colorindex_ci;
   JSAMPROW colormap_ci;
   int pixcode;
   int nc = cinfo->out_color_components;
   int dir;			/* 1 for left-to-right, -1 for right-to-left */
   int dirnc;			/* dir * nc */
   int ci;
   int row;
   JDIMENSION col;
   JDIMENSION width = cinfo->output_width;
   JSAMPLE *range_limit = cinfo->sample_range_limit;
   SHIFT_TEMPS
   for (row = 0; row < num_rows; row++) {
     /* Initialize output values to 0 so can process components separately */
     jzero_far((void FAR *) output_buf[row],
 	      (size_t) (width * SIZEOF(JSAMPLE)));
     for (ci = 0; ci < nc; ci++) {
       input_ptr = input_buf[row] + ci;
       output_ptr = output_buf[row];
       if (cquantize->on_odd_row) {
 	/* work right to left in this row */
 	input_ptr += (width-1) * nc; /* so point to rightmost pixel */
 	output_ptr += width-1;
 	dir = -1;
 	dirnc = -nc;
 	errorptr = cquantize->fserrors[ci] + (width+1); /* => entry after last column */
       } else {
 	/* work left to right in this row */
 	dir = 1;
 	dirnc = nc;
 	errorptr = cquantize->fserrors[ci]; /* => entry before first column */
       }
       colorindex_ci = cquantize->colorindex[ci];
       colormap_ci = cquantize->sv_colormap[ci];
       /* Preset error values: no error propagated to first pixel from left */
       cur = 0;
       /* and no error propagated to row below yet */
       belowerr = bpreverr = 0;
       for (col = width; col > 0; col--) {
 	/* cur holds the error propagated from the previous pixel on the
 	 * current line.  Add the error propagated from the previous line
 	 * to form the complete error correction term for this pixel, and
 	 * round the error term (which is expressed * 16) to an integer.
 	 * RIGHT_SHIFT rounds towards minus infinity, so adding 8 is correct
 	 * for either sign of the error value.
 	 * Note: errorptr points to *previous* column's array entry.
 	 */
 	cur = RIGHT_SHIFT(cur + errorptr[dir] + 8, 4);
 	/* Form pixel value + error, and range-limit to 0..MAXJSAMPLE.
 	 * The maximum error is +- MAXJSAMPLE; this sets the required size
 	 * of the range_limit array.
 	 */
 	cur += GETJSAMPLE(*input_ptr);
 	cur = GETJSAMPLE(range_limit[cur]);
 	/* Select output value, accumulate into output code for this pixel */
 	pixcode = GETJSAMPLE(colorindex_ci[cur]);
 	*output_ptr += (JSAMPLE) pixcode;
 	/* Compute actual representation error at this pixel */
 	/* Note: we can do this even though we don't have the final */
 	/* pixel code, because the colormap is orthogonal. */
 	cur -= GETJSAMPLE(colormap_ci[pixcode]);
 	/* Compute error fractions to be propagated to adjacent pixels.
 	 * Add these into the running sums, and simultaneously shift the
 	 * next-line error sums left by 1 column.
 	 */
 	bnexterr = cur;
 	delta = cur * 2;
 	cur += delta;		/* form error * 3 */
 	errorptr[0] = (FSERROR) (bpreverr + cur);
 	cur += delta;		/* form error * 5 */
 	bpreverr = belowerr + cur;
 	belowerr = bnexterr;
 	cur += delta;		/* form error * 7 */
 	/* At this point cur contains the 7/16 error value to be propagated
 	 * to the next pixel on the current line, and all the errors for the
 	 * next line have been shifted over. We are therefore ready to move on.
 	 */
 	input_ptr += dirnc;	/* advance input ptr to next column */
 	output_ptr += dir;	/* advance output ptr to next column */
 	errorptr += dir;	/* advance errorptr to current column */
       }
       /* Post-loop cleanup: we must unload the final error value into the
        * final fserrors[] entry.  Note we need not unload belowerr because
        * it is for the dummy column before or after the actual array.
        */
       errorptr[0] = (FSERROR) bpreverr; /* unload prev err into array */
     }
     cquantize->on_odd_row = (cquantize->on_odd_row ? FALSE : TRUE);
   }
 }
 /*
  * Allocate workspace for Floyd-Steinberg errors.
  */
 LOCAL(void)
 alloc_fs_workspace (j_decompress_ptr cinfo)
 {
   my_cquantize_ptr cquantize = (my_cquantize_ptr) cinfo->cquantize;
   size_t arraysize;
   int i;
   arraysize = (size_t) ((cinfo->output_width + 2) * SIZEOF(FSERROR));
   for (i = 0; i < cinfo->out_color_components; i++) {
     cquantize->fserrors[i] = (FSERRPTR)
       (*cinfo->mem->alloc_large)((j_common_ptr) cinfo, JPOOL_IMAGE, arraysize);
   }
 }
 /*
  * Initialize for one-pass color quantization.
  */
 METHODDEF(void)
 start_pass_1_quant (j_decompress_ptr cinfo, boolean is_pre_scan)
 {
   my_cquantize_ptr cquantize = (my_cquantize_ptr) cinfo->cquantize;
   size_t arraysize;
   int i;
   /* Install my colormap. */
   cinfo->colormap = cquantize->sv_colormap;
   cinfo->actual_number_of_colors = cquantize->sv_actual;
   /* Initialize for desired dithering mode. */
   switch (cinfo->dither_mode) {
   case JDITHER_NONE:
     if (cinfo->out_color_components == 3)
       cquantize->pub.color_quantize = color_quantize3;
     else
       cquantize->pub.color_quantize = color_quantize;
     break;
   case JDITHER_ORDERED:
     if (cinfo->out_color_components == 3)
       cquantize->pub.color_quantize = quantize3_ord_dither;
     else
       cquantize->pub.color_quantize = quantize_ord_dither;
     cquantize->row_index = 0;	/* initialize state for ordered dither */
     /* If user changed to ordered dither from another mode,
      * we must recreate the color index table with padding.
      * This will cost extra space, but probably isn't very likely.
      */
     if (! cquantize->is_padded)
       create_colorindex(cinfo);
     /* Create ordered-dither tables if we didn't already. */
     if (cquantize->odither[0] == NULL)
       create_odither_tables(cinfo);
     break;
   case JDITHER_FS:
     cquantize->pub.color_quantize = quantize_fs_dither;
     cquantize->on_odd_row = FALSE; /* initialize state for F-S dither */
     /* Allocate Floyd-Steinberg workspace if didn't already. */
     if (cquantize->fserrors[0] == NULL)
       alloc_fs_workspace(cinfo);
     /* Initialize the propagated errors to zero. */
     arraysize = (size_t) ((cinfo->output_width + 2) * SIZEOF(FSERROR));
     for (i = 0; i < cinfo->out_color_components; i++)
       jzero_far((void FAR *) cquantize->fserrors[i], arraysize);
     break;
   default:
     ERREXIT(cinfo, JERR_NOT_COMPILED);
     break;
   }
 }
 /*
  * Finish up at the end of the pass.
  */
 METHODDEF(void)
 finish_pass_1_quant (j_decompress_ptr cinfo)
 {
   /* no work in 1-pass case */
 }
 /*
  * Switch to a new external colormap between output passes.
  * Shouldn't get to this module!
  */
 METHODDEF(void)
 new_color_map_1_quant (j_decompress_ptr cinfo)
 {
   ERREXIT(cinfo, JERR_MODE_CHANGE);
 }
 /*
  * Module initialization routine for 1-pass color quantization.
  */
 GLOBAL(void)
 jinit_1pass_quantizer (j_decompress_ptr cinfo)
 {
   my_cquantize_ptr cquantize;
   cquantize = (my_cquantize_ptr)
     (*cinfo->mem->alloc_small) ((j_common_ptr) cinfo, JPOOL_IMAGE,
 				SIZEOF(my_cquantizer));
   cinfo->cquantize = (struct jpeg_color_quantizer *) cquantize;
   cquantize->pub.start_pass = start_pass_1_quant;
   cquantize->pub.finish_pass = finish_pass_1_quant;
   cquantize->pub.new_color_map = new_color_map_1_quant;
   cquantize->fserrors[0] = NULL; /* Flag FS workspace not allocated */
   cquantize->odither[0] = NULL;	/* Also flag odither arrays not allocated */
   /* Make sure my internal arrays won't overflow */
   if (cinfo->out_color_components > MAX_Q_COMPS)
     ERREXIT1(cinfo, JERR_QUANT_COMPONENTS, MAX_Q_COMPS);
   /* Make sure colormap indexes can be represented by JSAMPLEs */
   if (cinfo->desired_number_of_colors > (MAXJSAMPLE+1))
     ERREXIT1(cinfo, JERR_QUANT_MANY_COLORS, MAXJSAMPLE+1);
   /* Create the colormap and color index table. */
   create_colormap(cinfo);
   create_colorindex(cinfo);
   /* Allocate Floyd-Steinberg workspace now if requested.
    * We do this now since it is FAR storage and may affect the memory
    * manager's space calculations.  If the user changes to FS dither
    * mode in a later pass, we will allocate the space then, and will
    * possibly overrun the max_memory_to_use setting.
    */
   if (cinfo->dither_mode == JDITHER_FS)
     alloc_fs_workspace(cinfo);
 }
 #endif /* QUANT_1PASS_SUPPORTED */

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media/libjpeg/jquant1.c@b8a032363ba2 (annotated)

media/libjpeg/jquant1.c