/* * 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 == 8typedef INT16 FSERROR; /* 16 bits should be enough */typedef int LOCFSERROR; /* use 'int' for calculation temps */#elsetypedef 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; Lines 1–500 of 856. 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/* * 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;