| /* |
| * 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, 2015, 2022, D. R. Commander. |
| * For conditions of distribution and use, see the accompanying README.ijg |
| * 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" |
| #include "jsamplecomp.h" |
| |
| #if defined(QUANT_1PASS_SUPPORTED) && \ |
| (BITS_IN_JSAMPLE != 16 || defined(D_LOSSLESS_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. |
| */ |
| |
| #if BITS_IN_JSAMPLE == 8 |
| typedef INT16 FSERROR; /* 16 bits should be enough */ |
| typedef int LOCFSERROR; /* use 'int' for calculation temps */ |
| #else |
| typedef JLONG FSERROR; /* may need more than 16 bits */ |
| typedef JLONG LOCFSERROR; /* be sure calculation temps are big enough */ |
| #endif |
| |
| typedef FSERROR *FSERRPTR; /* pointer to error array */ |
| |
| |
| /* 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 allocated 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)(((JLONG)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)(((JLONG)(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 = (_JSAMPARRAY)(*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 = (_JSAMPARRAY)(*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; |
| JLONG 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 * ((JLONG)(ncolors - 1)); |
| for (j = 0; j < ODITHER_SIZE; j++) { |
| for (k = 0; k < ODITHER_SIZE; k++) { |
| num = ((JLONG)(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 += colorindex[ci][*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 = colorindex0[*ptrin++]; |
| pixcode += colorindex1[*ptrin++]; |
| pixcode += colorindex2[*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 *)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[*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 = colorindex0[(*input_ptr++) + dither0[col_index]]; |
| pixcode += colorindex1[(*input_ptr++) + dither1[col_index]]; |
| pixcode += colorindex2[(*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 = (_JSAMPLE *)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 *)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 += *input_ptr; |
| cur = range_limit[cur]; |
| /* Select output value, accumulate into output code for this pixel */ |
| pixcode = 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 -= 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 = (JSAMPARRAY)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 *)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; |
| |
| if (cinfo->data_precision != BITS_IN_JSAMPLE) |
| ERREXIT1(cinfo, JERR_BAD_PRECISION, cinfo->data_precision); |
| |
| 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 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 /* defined(QUANT_1PASS_SUPPORTED) && |
| (BITS_IN_JSAMPLE != 16 || defined(D_LOSSLESS_SUPPORTED)) */ |