--- /dev/null
+/*
+ * jquant1.c
+ *
+ * Copyright (C) 1991-1996, Thomas G. Lane.
+ * This file is part of the Independent JPEG Group's software.
+ * 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;
+ static const int RGB_order[3] = { RGB_GREEN, RGB_RED, RGB_BLUE };
+
+ /* 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 */
projects / eradicate / blobdiff