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Diffstat (limited to 'jpg/jquant1.c')
| -rw-r--r-- | jpg/jquant1.c | 857 |
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diff --git a/jpg/jquant1.c b/jpg/jquant1.c deleted file mode 100644 index 9d11f70..0000000 --- a/jpg/jquant1.c +++ /dev/null @@ -1,857 +0,0 @@ -/* - * jquant1.c - * - * Copyright (C) 1991-1996, Thomas G. Lane. - * Modified 2011 by Guido Vollbeding. - * 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 */ - FMEMZERO((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 */ - FMEMZERO((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++) - FMEMZERO((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 */ |