The Tor Browser: comparison media/libjpeg/jquant1.c

--1:000000000000
+:bd92ae813e8c
+/*
+* 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 */

The Tor Browser / file comparison

comparison: media/libjpeg/jquant1.c

media/libjpeg/jquant1.c