source: rtems-graphics-toolkit/jpeg-8d/jquant1.c @ 86b99f7

Last change on this file since 86b99f7 was 86b99f7, checked in by Alexandru-Sever Horin <alex.sever.h@…>, on Aug 1, 2012 at 10:40:32 PM

Added jpeg-8d version. Made modifications to compile for RTEMS, without man or binaries

  • Property mode set to 100644
File size: 30.6 KB
Line 
1/*
2 * jquant1.c
3 *
4 * Copyright (C) 1991-1996, Thomas G. Lane.
5 * Modified 2011 by Guido Vollbeding.
6 * This file is part of the Independent JPEG Group's software.
7 * For conditions of distribution and use, see the accompanying README file.
8 *
9 * This file contains 1-pass color quantization (color mapping) routines.
10 * These routines provide mapping to a fixed color map using equally spaced
11 * color values.  Optional Floyd-Steinberg or ordered dithering is available.
12 */
13
14#define JPEG_INTERNALS
15#include "jinclude.h"
16#include "jpeglib.h"
17
18#ifdef QUANT_1PASS_SUPPORTED
19
20
21/*
22 * The main purpose of 1-pass quantization is to provide a fast, if not very
23 * high quality, colormapped output capability.  A 2-pass quantizer usually
24 * gives better visual quality; however, for quantized grayscale output this
25 * quantizer is perfectly adequate.  Dithering is highly recommended with this
26 * quantizer, though you can turn it off if you really want to.
27 *
28 * In 1-pass quantization the colormap must be chosen in advance of seeing the
29 * image.  We use a map consisting of all combinations of Ncolors[i] color
30 * values for the i'th component.  The Ncolors[] values are chosen so that
31 * their product, the total number of colors, is no more than that requested.
32 * (In most cases, the product will be somewhat less.)
33 *
34 * Since the colormap is orthogonal, the representative value for each color
35 * component can be determined without considering the other components;
36 * then these indexes can be combined into a colormap index by a standard
37 * N-dimensional-array-subscript calculation.  Most of the arithmetic involved
38 * can be precalculated and stored in the lookup table colorindex[].
39 * colorindex[i][j] maps pixel value j in component i to the nearest
40 * representative value (grid plane) for that component; this index is
41 * multiplied by the array stride for component i, so that the
42 * index of the colormap entry closest to a given pixel value is just
43 *    sum( colorindex[component-number][pixel-component-value] )
44 * Aside from being fast, this scheme allows for variable spacing between
45 * representative values with no additional lookup cost.
46 *
47 * If gamma correction has been applied in color conversion, it might be wise
48 * to adjust the color grid spacing so that the representative colors are
49 * equidistant in linear space.  At this writing, gamma correction is not
50 * implemented by jdcolor, so nothing is done here.
51 */
52
53
54/* Declarations for ordered dithering.
55 *
56 * We use a standard 16x16 ordered dither array.  The basic concept of ordered
57 * dithering is described in many references, for instance Dale Schumacher's
58 * chapter II.2 of Graphics Gems II (James Arvo, ed. Academic Press, 1991).
59 * In place of Schumacher's comparisons against a "threshold" value, we add a
60 * "dither" value to the input pixel and then round the result to the nearest
61 * output value.  The dither value is equivalent to (0.5 - threshold) times
62 * the distance between output values.  For ordered dithering, we assume that
63 * the output colors are equally spaced; if not, results will probably be
64 * worse, since the dither may be too much or too little at a given point.
65 *
66 * The normal calculation would be to form pixel value + dither, range-limit
67 * this to 0..MAXJSAMPLE, and then index into the colorindex table as usual.
68 * We can skip the separate range-limiting step by extending the colorindex
69 * table in both directions.
70 */
71
72#define ODITHER_SIZE  16        /* dimension of dither matrix */
73/* NB: if ODITHER_SIZE is not a power of 2, ODITHER_MASK uses will break */
74#define ODITHER_CELLS (ODITHER_SIZE*ODITHER_SIZE)       /* # cells in matrix */
75#define ODITHER_MASK  (ODITHER_SIZE-1) /* mask for wrapping around counters */
76
77typedef int ODITHER_MATRIX[ODITHER_SIZE][ODITHER_SIZE];
78typedef int (*ODITHER_MATRIX_PTR)[ODITHER_SIZE];
79
80static const UINT8 base_dither_matrix[ODITHER_SIZE][ODITHER_SIZE] = {
81  /* Bayer's order-4 dither array.  Generated by the code given in
82   * Stephen Hawley's article "Ordered Dithering" in Graphics Gems I.
83   * The values in this array must range from 0 to ODITHER_CELLS-1.
84   */
85  {   0,192, 48,240, 12,204, 60,252,  3,195, 51,243, 15,207, 63,255 },
86  { 128, 64,176,112,140, 76,188,124,131, 67,179,115,143, 79,191,127 },
87  {  32,224, 16,208, 44,236, 28,220, 35,227, 19,211, 47,239, 31,223 },
88  { 160, 96,144, 80,172,108,156, 92,163, 99,147, 83,175,111,159, 95 },
89  {   8,200, 56,248,  4,196, 52,244, 11,203, 59,251,  7,199, 55,247 },
90  { 136, 72,184,120,132, 68,180,116,139, 75,187,123,135, 71,183,119 },
91  {  40,232, 24,216, 36,228, 20,212, 43,235, 27,219, 39,231, 23,215 },
92  { 168,104,152, 88,164,100,148, 84,171,107,155, 91,167,103,151, 87 },
93  {   2,194, 50,242, 14,206, 62,254,  1,193, 49,241, 13,205, 61,253 },
94  { 130, 66,178,114,142, 78,190,126,129, 65,177,113,141, 77,189,125 },
95  {  34,226, 18,210, 46,238, 30,222, 33,225, 17,209, 45,237, 29,221 },
96  { 162, 98,146, 82,174,110,158, 94,161, 97,145, 81,173,109,157, 93 },
97  {  10,202, 58,250,  6,198, 54,246,  9,201, 57,249,  5,197, 53,245 },
98  { 138, 74,186,122,134, 70,182,118,137, 73,185,121,133, 69,181,117 },
99  {  42,234, 26,218, 38,230, 22,214, 41,233, 25,217, 37,229, 21,213 },
100  { 170,106,154, 90,166,102,150, 86,169,105,153, 89,165,101,149, 85 }
101};
102
103
104/* Declarations for Floyd-Steinberg dithering.
105 *
106 * Errors are accumulated into the array fserrors[], at a resolution of
107 * 1/16th of a pixel count.  The error at a given pixel is propagated
108 * to its not-yet-processed neighbors using the standard F-S fractions,
109 *              ...     (here)  7/16
110 *              3/16    5/16    1/16
111 * We work left-to-right on even rows, right-to-left on odd rows.
112 *
113 * We can get away with a single array (holding one row's worth of errors)
114 * by using it to store the current row's errors at pixel columns not yet
115 * processed, but the next row's errors at columns already processed.  We
116 * need only a few extra variables to hold the errors immediately around the
117 * current column.  (If we are lucky, those variables are in registers, but
118 * even if not, they're probably cheaper to access than array elements are.)
119 *
120 * The fserrors[] array is indexed [component#][position].
121 * We provide (#columns + 2) entries per component; the extra entry at each
122 * end saves us from special-casing the first and last pixels.
123 *
124 * Note: on a wide image, we might not have enough room in a PC's near data
125 * segment to hold the error array; so it is allocated with alloc_large.
126 */
127
128#if BITS_IN_JSAMPLE == 8
129typedef INT16 FSERROR;          /* 16 bits should be enough */
130typedef int LOCFSERROR;         /* use 'int' for calculation temps */
131#else
132typedef INT32 FSERROR;          /* may need more than 16 bits */
133typedef INT32 LOCFSERROR;       /* be sure calculation temps are big enough */
134#endif
135
136typedef FSERROR FAR *FSERRPTR;  /* pointer to error array (in FAR storage!) */
137
138
139/* Private subobject */
140
141#define MAX_Q_COMPS 4           /* max components I can handle */
142
143typedef struct {
144  struct jpeg_color_quantizer pub; /* public fields */
145
146  /* Initially allocated colormap is saved here */
147  JSAMPARRAY sv_colormap;       /* The color map as a 2-D pixel array */
148  int sv_actual;                /* number of entries in use */
149
150  JSAMPARRAY colorindex;        /* Precomputed mapping for speed */
151  /* colorindex[i][j] = index of color closest to pixel value j in component i,
152   * premultiplied as described above.  Since colormap indexes must fit into
153   * JSAMPLEs, the entries of this array will too.
154   */
155  boolean is_padded;            /* is the colorindex padded for odither? */
156
157  int Ncolors[MAX_Q_COMPS];     /* # of values alloced to each component */
158
159  /* Variables for ordered dithering */
160  int row_index;                /* cur row's vertical index in dither matrix */
161  ODITHER_MATRIX_PTR odither[MAX_Q_COMPS]; /* one dither array per component */
162
163  /* Variables for Floyd-Steinberg dithering */
164  FSERRPTR fserrors[MAX_Q_COMPS]; /* accumulated errors */
165  boolean on_odd_row;           /* flag to remember which row we are on */
166} my_cquantizer;
167
168typedef my_cquantizer * my_cquantize_ptr;
169
170
171/*
172 * Policy-making subroutines for create_colormap and create_colorindex.
173 * These routines determine the colormap to be used.  The rest of the module
174 * only assumes that the colormap is orthogonal.
175 *
176 *  * select_ncolors decides how to divvy up the available colors
177 *    among the components.
178 *  * output_value defines the set of representative values for a component.
179 *  * largest_input_value defines the mapping from input values to
180 *    representative values for a component.
181 * Note that the latter two routines may impose different policies for
182 * different components, though this is not currently done.
183 */
184
185
186LOCAL(int)
187select_ncolors (j_decompress_ptr cinfo, int Ncolors[])
188/* Determine allocation of desired colors to components, */
189/* and fill in Ncolors[] array to indicate choice. */
190/* Return value is total number of colors (product of Ncolors[] values). */
191{
192  int nc = cinfo->out_color_components; /* number of color components */
193  int max_colors = cinfo->desired_number_of_colors;
194  int total_colors, iroot, i, j;
195  boolean changed;
196  long temp;
197  static const int RGB_order[3] = { RGB_GREEN, RGB_RED, RGB_BLUE };
198
199  /* We can allocate at least the nc'th root of max_colors per component. */
200  /* Compute floor(nc'th root of max_colors). */
201  iroot = 1;
202  do {
203    iroot++;
204    temp = iroot;               /* set temp = iroot ** nc */
205    for (i = 1; i < nc; i++)
206      temp *= iroot;
207  } while (temp <= (long) max_colors); /* repeat till iroot exceeds root */
208  iroot--;                      /* now iroot = floor(root) */
209
210  /* Must have at least 2 color values per component */
211  if (iroot < 2)
212    ERREXIT1(cinfo, JERR_QUANT_FEW_COLORS, (int) temp);
213
214  /* Initialize to iroot color values for each component */
215  total_colors = 1;
216  for (i = 0; i < nc; i++) {
217    Ncolors[i] = iroot;
218    total_colors *= iroot;
219  }
220  /* We may be able to increment the count for one or more components without
221   * exceeding max_colors, though we know not all can be incremented.
222   * Sometimes, the first component can be incremented more than once!
223   * (Example: for 16 colors, we start at 2*2*2, go to 3*2*2, then 4*2*2.)
224   * In RGB colorspace, try to increment G first, then R, then B.
225   */
226  do {
227    changed = FALSE;
228    for (i = 0; i < nc; i++) {
229      j = (cinfo->out_color_space == JCS_RGB ? RGB_order[i] : i);
230      /* calculate new total_colors if Ncolors[j] is incremented */
231      temp = total_colors / Ncolors[j];
232      temp *= Ncolors[j]+1;     /* done in long arith to avoid oflo */
233      if (temp > (long) max_colors)
234        break;                  /* won't fit, done with this pass */
235      Ncolors[j]++;             /* OK, apply the increment */
236      total_colors = (int) temp;
237      changed = TRUE;
238    }
239  } while (changed);
240
241  return total_colors;
242}
243
244
245LOCAL(int)
246output_value (j_decompress_ptr cinfo, int ci, int j, int maxj)
247/* Return j'th output value, where j will range from 0 to maxj */
248/* The output values must fall in 0..MAXJSAMPLE in increasing order */
249{
250  /* We always provide values 0 and MAXJSAMPLE for each component;
251   * any additional values are equally spaced between these limits.
252   * (Forcing the upper and lower values to the limits ensures that
253   * dithering can't produce a color outside the selected gamut.)
254   */
255  return (int) (((INT32) j * MAXJSAMPLE + maxj/2) / maxj);
256}
257
258
259LOCAL(int)
260largest_input_value (j_decompress_ptr cinfo, int ci, int j, int maxj)
261/* Return largest input value that should map to j'th output value */
262/* Must have largest(j=0) >= 0, and largest(j=maxj) >= MAXJSAMPLE */
263{
264  /* Breakpoints are halfway between values returned by output_value */
265  return (int) (((INT32) (2*j + 1) * MAXJSAMPLE + maxj) / (2*maxj));
266}
267
268
269/*
270 * Create the colormap.
271 */
272
273LOCAL(void)
274create_colormap (j_decompress_ptr cinfo)
275{
276  my_cquantize_ptr cquantize = (my_cquantize_ptr) cinfo->cquantize;
277  JSAMPARRAY colormap;          /* Created colormap */
278  int total_colors;             /* Number of distinct output colors */
279  int i,j,k, nci, blksize, blkdist, ptr, val;
280
281  /* Select number of colors for each component */
282  total_colors = select_ncolors(cinfo, cquantize->Ncolors);
283
284  /* Report selected color counts */
285  if (cinfo->out_color_components == 3)
286    TRACEMS4(cinfo, 1, JTRC_QUANT_3_NCOLORS,
287             total_colors, cquantize->Ncolors[0],
288             cquantize->Ncolors[1], cquantize->Ncolors[2]);
289  else
290    TRACEMS1(cinfo, 1, JTRC_QUANT_NCOLORS, total_colors);
291
292  /* Allocate and fill in the colormap. */
293  /* The colors are ordered in the map in standard row-major order, */
294  /* i.e. rightmost (highest-indexed) color changes most rapidly. */
295
296  colormap = (*cinfo->mem->alloc_sarray)
297    ((j_common_ptr) cinfo, JPOOL_IMAGE,
298     (JDIMENSION) total_colors, (JDIMENSION) cinfo->out_color_components);
299
300  /* blksize is number of adjacent repeated entries for a component */
301  /* blkdist is distance between groups of identical entries for a component */
302  blkdist = total_colors;
303
304  for (i = 0; i < cinfo->out_color_components; i++) {
305    /* fill in colormap entries for i'th color component */
306    nci = cquantize->Ncolors[i]; /* # of distinct values for this color */
307    blksize = blkdist / nci;
308    for (j = 0; j < nci; j++) {
309      /* Compute j'th output value (out of nci) for component */
310      val = output_value(cinfo, i, j, nci-1);
311      /* Fill in all colormap entries that have this value of this component */
312      for (ptr = j * blksize; ptr < total_colors; ptr += blkdist) {
313        /* fill in blksize entries beginning at ptr */
314        for (k = 0; k < blksize; k++)
315          colormap[i][ptr+k] = (JSAMPLE) val;
316      }
317    }
318    blkdist = blksize;          /* blksize of this color is blkdist of next */
319  }
320
321  /* Save the colormap in private storage,
322   * where it will survive color quantization mode changes.
323   */
324  cquantize->sv_colormap = colormap;
325  cquantize->sv_actual = total_colors;
326}
327
328
329/*
330 * Create the color index table.
331 */
332
333LOCAL(void)
334create_colorindex (j_decompress_ptr cinfo)
335{
336  my_cquantize_ptr cquantize = (my_cquantize_ptr) cinfo->cquantize;
337  JSAMPROW indexptr;
338  int i,j,k, nci, blksize, val, pad;
339
340  /* For ordered dither, we pad the color index tables by MAXJSAMPLE in
341   * each direction (input index values can be -MAXJSAMPLE .. 2*MAXJSAMPLE).
342   * This is not necessary in the other dithering modes.  However, we
343   * flag whether it was done in case user changes dithering mode.
344   */
345  if (cinfo->dither_mode == JDITHER_ORDERED) {
346    pad = MAXJSAMPLE*2;
347    cquantize->is_padded = TRUE;
348  } else {
349    pad = 0;
350    cquantize->is_padded = FALSE;
351  }
352
353  cquantize->colorindex = (*cinfo->mem->alloc_sarray)
354    ((j_common_ptr) cinfo, JPOOL_IMAGE,
355     (JDIMENSION) (MAXJSAMPLE+1 + pad),
356     (JDIMENSION) cinfo->out_color_components);
357
358  /* blksize is number of adjacent repeated entries for a component */
359  blksize = cquantize->sv_actual;
360
361  for (i = 0; i < cinfo->out_color_components; i++) {
362    /* fill in colorindex entries for i'th color component */
363    nci = cquantize->Ncolors[i]; /* # of distinct values for this color */
364    blksize = blksize / nci;
365
366    /* adjust colorindex pointers to provide padding at negative indexes. */
367    if (pad)
368      cquantize->colorindex[i] += MAXJSAMPLE;
369
370    /* in loop, val = index of current output value, */
371    /* and k = largest j that maps to current val */
372    indexptr = cquantize->colorindex[i];
373    val = 0;
374    k = largest_input_value(cinfo, i, 0, nci-1);
375    for (j = 0; j <= MAXJSAMPLE; j++) {
376      while (j > k)             /* advance val if past boundary */
377        k = largest_input_value(cinfo, i, ++val, nci-1);
378      /* premultiply so that no multiplication needed in main processing */
379      indexptr[j] = (JSAMPLE) (val * blksize);
380    }
381    /* Pad at both ends if necessary */
382    if (pad)
383      for (j = 1; j <= MAXJSAMPLE; j++) {
384        indexptr[-j] = indexptr[0];
385        indexptr[MAXJSAMPLE+j] = indexptr[MAXJSAMPLE];
386      }
387  }
388}
389
390
391/*
392 * Create an ordered-dither array for a component having ncolors
393 * distinct output values.
394 */
395
396LOCAL(ODITHER_MATRIX_PTR)
397make_odither_array (j_decompress_ptr cinfo, int ncolors)
398{
399  ODITHER_MATRIX_PTR odither;
400  int j,k;
401  INT32 num,den;
402
403  odither = (ODITHER_MATRIX_PTR)
404    (*cinfo->mem->alloc_small) ((j_common_ptr) cinfo, JPOOL_IMAGE,
405                                SIZEOF(ODITHER_MATRIX));
406  /* The inter-value distance for this color is MAXJSAMPLE/(ncolors-1).
407   * Hence the dither value for the matrix cell with fill order f
408   * (f=0..N-1) should be (N-1-2*f)/(2*N) * MAXJSAMPLE/(ncolors-1).
409   * On 16-bit-int machine, be careful to avoid overflow.
410   */
411  den = 2 * ODITHER_CELLS * ((INT32) (ncolors - 1));
412  for (j = 0; j < ODITHER_SIZE; j++) {
413    for (k = 0; k < ODITHER_SIZE; k++) {
414      num = ((INT32) (ODITHER_CELLS-1 - 2*((int)base_dither_matrix[j][k])))
415            * MAXJSAMPLE;
416      /* Ensure round towards zero despite C's lack of consistency
417       * about rounding negative values in integer division...
418       */
419      odither[j][k] = (int) (num<0 ? -((-num)/den) : num/den);
420    }
421  }
422  return odither;
423}
424
425
426/*
427 * Create the ordered-dither tables.
428 * Components having the same number of representative colors may
429 * share a dither table.
430 */
431
432LOCAL(void)
433create_odither_tables (j_decompress_ptr cinfo)
434{
435  my_cquantize_ptr cquantize = (my_cquantize_ptr) cinfo->cquantize;
436  ODITHER_MATRIX_PTR odither;
437  int i, j, nci;
438
439  for (i = 0; i < cinfo->out_color_components; i++) {
440    nci = cquantize->Ncolors[i]; /* # of distinct values for this color */
441    odither = NULL;             /* search for matching prior component */
442    for (j = 0; j < i; j++) {
443      if (nci == cquantize->Ncolors[j]) {
444        odither = cquantize->odither[j];
445        break;
446      }
447    }
448    if (odither == NULL)        /* need a new table? */
449      odither = make_odither_array(cinfo, nci);
450    cquantize->odither[i] = odither;
451  }
452}
453
454
455/*
456 * Map some rows of pixels to the output colormapped representation.
457 */
458
459METHODDEF(void)
460color_quantize (j_decompress_ptr cinfo, JSAMPARRAY input_buf,
461                JSAMPARRAY output_buf, int num_rows)
462/* General case, no dithering */
463{
464  my_cquantize_ptr cquantize = (my_cquantize_ptr) cinfo->cquantize;
465  JSAMPARRAY colorindex = cquantize->colorindex;
466  register int pixcode, ci;
467  register JSAMPROW ptrin, ptrout;
468  int row;
469  JDIMENSION col;
470  JDIMENSION width = cinfo->output_width;
471  register int nc = cinfo->out_color_components;
472
473  for (row = 0; row < num_rows; row++) {
474    ptrin = input_buf[row];
475    ptrout = output_buf[row];
476    for (col = width; col > 0; col--) {
477      pixcode = 0;
478      for (ci = 0; ci < nc; ci++) {
479        pixcode += GETJSAMPLE(colorindex[ci][GETJSAMPLE(*ptrin++)]);
480      }
481      *ptrout++ = (JSAMPLE) pixcode;
482    }
483  }
484}
485
486
487METHODDEF(void)
488color_quantize3 (j_decompress_ptr cinfo, JSAMPARRAY input_buf,
489                 JSAMPARRAY output_buf, int num_rows)
490/* Fast path for out_color_components==3, no dithering */
491{
492  my_cquantize_ptr cquantize = (my_cquantize_ptr) cinfo->cquantize;
493  register int pixcode;
494  register JSAMPROW ptrin, ptrout;
495  JSAMPROW colorindex0 = cquantize->colorindex[0];
496  JSAMPROW colorindex1 = cquantize->colorindex[1];
497  JSAMPROW colorindex2 = cquantize->colorindex[2];
498  int row;
499  JDIMENSION col;
500  JDIMENSION width = cinfo->output_width;
501
502  for (row = 0; row < num_rows; row++) {
503    ptrin = input_buf[row];
504    ptrout = output_buf[row];
505    for (col = width; col > 0; col--) {
506      pixcode  = GETJSAMPLE(colorindex0[GETJSAMPLE(*ptrin++)]);
507      pixcode += GETJSAMPLE(colorindex1[GETJSAMPLE(*ptrin++)]);
508      pixcode += GETJSAMPLE(colorindex2[GETJSAMPLE(*ptrin++)]);
509      *ptrout++ = (JSAMPLE) pixcode;
510    }
511  }
512}
513
514
515METHODDEF(void)
516quantize_ord_dither (j_decompress_ptr cinfo, JSAMPARRAY input_buf,
517                     JSAMPARRAY output_buf, int num_rows)
518/* General case, with ordered dithering */
519{
520  my_cquantize_ptr cquantize = (my_cquantize_ptr) cinfo->cquantize;
521  register JSAMPROW input_ptr;
522  register JSAMPROW output_ptr;
523  JSAMPROW colorindex_ci;
524  int * dither;                 /* points to active row of dither matrix */
525  int row_index, col_index;     /* current indexes into dither matrix */
526  int nc = cinfo->out_color_components;
527  int ci;
528  int row;
529  JDIMENSION col;
530  JDIMENSION width = cinfo->output_width;
531
532  for (row = 0; row < num_rows; row++) {
533    /* Initialize output values to 0 so can process components separately */
534    FMEMZERO((void FAR *) output_buf[row],
535             (size_t) (width * SIZEOF(JSAMPLE)));
536    row_index = cquantize->row_index;
537    for (ci = 0; ci < nc; ci++) {
538      input_ptr = input_buf[row] + ci;
539      output_ptr = output_buf[row];
540      colorindex_ci = cquantize->colorindex[ci];
541      dither = cquantize->odither[ci][row_index];
542      col_index = 0;
543
544      for (col = width; col > 0; col--) {
545        /* Form pixel value + dither, range-limit to 0..MAXJSAMPLE,
546         * select output value, accumulate into output code for this pixel.
547         * Range-limiting need not be done explicitly, as we have extended
548         * the colorindex table to produce the right answers for out-of-range
549         * inputs.  The maximum dither is +- MAXJSAMPLE; this sets the
550         * required amount of padding.
551         */
552        *output_ptr += colorindex_ci[GETJSAMPLE(*input_ptr)+dither[col_index]];
553        input_ptr += nc;
554        output_ptr++;
555        col_index = (col_index + 1) & ODITHER_MASK;
556      }
557    }
558    /* Advance row index for next row */
559    row_index = (row_index + 1) & ODITHER_MASK;
560    cquantize->row_index = row_index;
561  }
562}
563
564
565METHODDEF(void)
566quantize3_ord_dither (j_decompress_ptr cinfo, JSAMPARRAY input_buf,
567                      JSAMPARRAY output_buf, int num_rows)
568/* Fast path for out_color_components==3, with ordered dithering */
569{
570  my_cquantize_ptr cquantize = (my_cquantize_ptr) cinfo->cquantize;
571  register int pixcode;
572  register JSAMPROW input_ptr;
573  register JSAMPROW output_ptr;
574  JSAMPROW colorindex0 = cquantize->colorindex[0];
575  JSAMPROW colorindex1 = cquantize->colorindex[1];
576  JSAMPROW colorindex2 = cquantize->colorindex[2];
577  int * dither0;                /* points to active row of dither matrix */
578  int * dither1;
579  int * dither2;
580  int row_index, col_index;     /* current indexes into dither matrix */
581  int row;
582  JDIMENSION col;
583  JDIMENSION width = cinfo->output_width;
584
585  for (row = 0; row < num_rows; row++) {
586    row_index = cquantize->row_index;
587    input_ptr = input_buf[row];
588    output_ptr = output_buf[row];
589    dither0 = cquantize->odither[0][row_index];
590    dither1 = cquantize->odither[1][row_index];
591    dither2 = cquantize->odither[2][row_index];
592    col_index = 0;
593
594    for (col = width; col > 0; col--) {
595      pixcode  = GETJSAMPLE(colorindex0[GETJSAMPLE(*input_ptr++) +
596                                        dither0[col_index]]);
597      pixcode += GETJSAMPLE(colorindex1[GETJSAMPLE(*input_ptr++) +
598                                        dither1[col_index]]);
599      pixcode += GETJSAMPLE(colorindex2[GETJSAMPLE(*input_ptr++) +
600                                        dither2[col_index]]);
601      *output_ptr++ = (JSAMPLE) pixcode;
602      col_index = (col_index + 1) & ODITHER_MASK;
603    }
604    row_index = (row_index + 1) & ODITHER_MASK;
605    cquantize->row_index = row_index;
606  }
607}
608
609
610METHODDEF(void)
611quantize_fs_dither (j_decompress_ptr cinfo, JSAMPARRAY input_buf,
612                    JSAMPARRAY output_buf, int num_rows)
613/* General case, with Floyd-Steinberg dithering */
614{
615  my_cquantize_ptr cquantize = (my_cquantize_ptr) cinfo->cquantize;
616  register LOCFSERROR cur;      /* current error or pixel value */
617  LOCFSERROR belowerr;          /* error for pixel below cur */
618  LOCFSERROR bpreverr;          /* error for below/prev col */
619  LOCFSERROR bnexterr;          /* error for below/next col */
620  LOCFSERROR delta;
621  register FSERRPTR errorptr;   /* => fserrors[] at column before current */
622  register JSAMPROW input_ptr;
623  register JSAMPROW output_ptr;
624  JSAMPROW colorindex_ci;
625  JSAMPROW colormap_ci;
626  int pixcode;
627  int nc = cinfo->out_color_components;
628  int dir;                      /* 1 for left-to-right, -1 for right-to-left */
629  int dirnc;                    /* dir * nc */
630  int ci;
631  int row;
632  JDIMENSION col;
633  JDIMENSION width = cinfo->output_width;
634  JSAMPLE *range_limit = cinfo->sample_range_limit;
635  SHIFT_TEMPS
636
637  for (row = 0; row < num_rows; row++) {
638    /* Initialize output values to 0 so can process components separately */
639    FMEMZERO((void FAR *) output_buf[row],
640             (size_t) (width * SIZEOF(JSAMPLE)));
641    for (ci = 0; ci < nc; ci++) {
642      input_ptr = input_buf[row] + ci;
643      output_ptr = output_buf[row];
644      if (cquantize->on_odd_row) {
645        /* work right to left in this row */
646        input_ptr += (width-1) * nc; /* so point to rightmost pixel */
647        output_ptr += width-1;
648        dir = -1;
649        dirnc = -nc;
650        errorptr = cquantize->fserrors[ci] + (width+1); /* => entry after last column */
651      } else {
652        /* work left to right in this row */
653        dir = 1;
654        dirnc = nc;
655        errorptr = cquantize->fserrors[ci]; /* => entry before first column */
656      }
657      colorindex_ci = cquantize->colorindex[ci];
658      colormap_ci = cquantize->sv_colormap[ci];
659      /* Preset error values: no error propagated to first pixel from left */
660      cur = 0;
661      /* and no error propagated to row below yet */
662      belowerr = bpreverr = 0;
663
664      for (col = width; col > 0; col--) {
665        /* cur holds the error propagated from the previous pixel on the
666         * current line.  Add the error propagated from the previous line
667         * to form the complete error correction term for this pixel, and
668         * round the error term (which is expressed * 16) to an integer.
669         * RIGHT_SHIFT rounds towards minus infinity, so adding 8 is correct
670         * for either sign of the error value.
671         * Note: errorptr points to *previous* column's array entry.
672         */
673        cur = RIGHT_SHIFT(cur + errorptr[dir] + 8, 4);
674        /* Form pixel value + error, and range-limit to 0..MAXJSAMPLE.
675         * The maximum error is +- MAXJSAMPLE; this sets the required size
676         * of the range_limit array.
677         */
678        cur += GETJSAMPLE(*input_ptr);
679        cur = GETJSAMPLE(range_limit[cur]);
680        /* Select output value, accumulate into output code for this pixel */
681        pixcode = GETJSAMPLE(colorindex_ci[cur]);
682        *output_ptr += (JSAMPLE) pixcode;
683        /* Compute actual representation error at this pixel */
684        /* Note: we can do this even though we don't have the final */
685        /* pixel code, because the colormap is orthogonal. */
686        cur -= GETJSAMPLE(colormap_ci[pixcode]);
687        /* Compute error fractions to be propagated to adjacent pixels.
688         * Add these into the running sums, and simultaneously shift the
689         * next-line error sums left by 1 column.
690         */
691        bnexterr = cur;
692        delta = cur * 2;
693        cur += delta;           /* form error * 3 */
694        errorptr[0] = (FSERROR) (bpreverr + cur);
695        cur += delta;           /* form error * 5 */
696        bpreverr = belowerr + cur;
697        belowerr = bnexterr;
698        cur += delta;           /* form error * 7 */
699        /* At this point cur contains the 7/16 error value to be propagated
700         * to the next pixel on the current line, and all the errors for the
701         * next line have been shifted over. We are therefore ready to move on.
702         */
703        input_ptr += dirnc;     /* advance input ptr to next column */
704        output_ptr += dir;      /* advance output ptr to next column */
705        errorptr += dir;        /* advance errorptr to current column */
706      }
707      /* Post-loop cleanup: we must unload the final error value into the
708       * final fserrors[] entry.  Note we need not unload belowerr because
709       * it is for the dummy column before or after the actual array.
710       */
711      errorptr[0] = (FSERROR) bpreverr; /* unload prev err into array */
712    }
713    cquantize->on_odd_row = (cquantize->on_odd_row ? FALSE : TRUE);
714  }
715}
716
717
718/*
719 * Allocate workspace for Floyd-Steinberg errors.
720 */
721
722LOCAL(void)
723alloc_fs_workspace (j_decompress_ptr cinfo)
724{
725  my_cquantize_ptr cquantize = (my_cquantize_ptr) cinfo->cquantize;
726  size_t arraysize;
727  int i;
728
729  arraysize = (size_t) ((cinfo->output_width + 2) * SIZEOF(FSERROR));
730  for (i = 0; i < cinfo->out_color_components; i++) {
731    cquantize->fserrors[i] = (FSERRPTR)
732      (*cinfo->mem->alloc_large)((j_common_ptr) cinfo, JPOOL_IMAGE, arraysize);
733  }
734}
735
736
737/*
738 * Initialize for one-pass color quantization.
739 */
740
741METHODDEF(void)
742start_pass_1_quant (j_decompress_ptr cinfo, boolean is_pre_scan)
743{
744  my_cquantize_ptr cquantize = (my_cquantize_ptr) cinfo->cquantize;
745  size_t arraysize;
746  int i;
747
748  /* Install my colormap. */
749  cinfo->colormap = cquantize->sv_colormap;
750  cinfo->actual_number_of_colors = cquantize->sv_actual;
751
752  /* Initialize for desired dithering mode. */
753  switch (cinfo->dither_mode) {
754  case JDITHER_NONE:
755    if (cinfo->out_color_components == 3)
756      cquantize->pub.color_quantize = color_quantize3;
757    else
758      cquantize->pub.color_quantize = color_quantize;
759    break;
760  case JDITHER_ORDERED:
761    if (cinfo->out_color_components == 3)
762      cquantize->pub.color_quantize = quantize3_ord_dither;
763    else
764      cquantize->pub.color_quantize = quantize_ord_dither;
765    cquantize->row_index = 0;   /* initialize state for ordered dither */
766    /* If user changed to ordered dither from another mode,
767     * we must recreate the color index table with padding.
768     * This will cost extra space, but probably isn't very likely.
769     */
770    if (! cquantize->is_padded)
771      create_colorindex(cinfo);
772    /* Create ordered-dither tables if we didn't already. */
773    if (cquantize->odither[0] == NULL)
774      create_odither_tables(cinfo);
775    break;
776  case JDITHER_FS:
777    cquantize->pub.color_quantize = quantize_fs_dither;
778    cquantize->on_odd_row = FALSE; /* initialize state for F-S dither */
779    /* Allocate Floyd-Steinberg workspace if didn't already. */
780    if (cquantize->fserrors[0] == NULL)
781      alloc_fs_workspace(cinfo);
782    /* Initialize the propagated errors to zero. */
783    arraysize = (size_t) ((cinfo->output_width + 2) * SIZEOF(FSERROR));
784    for (i = 0; i < cinfo->out_color_components; i++)
785      FMEMZERO((void FAR *) cquantize->fserrors[i], arraysize);
786    break;
787  default:
788    ERREXIT(cinfo, JERR_NOT_COMPILED);
789    break;
790  }
791}
792
793
794/*
795 * Finish up at the end of the pass.
796 */
797
798METHODDEF(void)
799finish_pass_1_quant (j_decompress_ptr cinfo)
800{
801  /* no work in 1-pass case */
802}
803
804
805/*
806 * Switch to a new external colormap between output passes.
807 * Shouldn't get to this module!
808 */
809
810METHODDEF(void)
811new_color_map_1_quant (j_decompress_ptr cinfo)
812{
813  ERREXIT(cinfo, JERR_MODE_CHANGE);
814}
815
816
817/*
818 * Module initialization routine for 1-pass color quantization.
819 */
820
821GLOBAL(void)
822jinit_1pass_quantizer (j_decompress_ptr cinfo)
823{
824  my_cquantize_ptr cquantize;
825
826  cquantize = (my_cquantize_ptr)
827    (*cinfo->mem->alloc_small) ((j_common_ptr) cinfo, JPOOL_IMAGE,
828                                SIZEOF(my_cquantizer));
829  cinfo->cquantize = (struct jpeg_color_quantizer *) cquantize;
830  cquantize->pub.start_pass = start_pass_1_quant;
831  cquantize->pub.finish_pass = finish_pass_1_quant;
832  cquantize->pub.new_color_map = new_color_map_1_quant;
833  cquantize->fserrors[0] = NULL; /* Flag FS workspace not allocated */
834  cquantize->odither[0] = NULL; /* Also flag odither arrays not allocated */
835
836  /* Make sure my internal arrays won't overflow */
837  if (cinfo->out_color_components > MAX_Q_COMPS)
838    ERREXIT1(cinfo, JERR_QUANT_COMPONENTS, MAX_Q_COMPS);
839  /* Make sure colormap indexes can be represented by JSAMPLEs */
840  if (cinfo->desired_number_of_colors > (MAXJSAMPLE+1))
841    ERREXIT1(cinfo, JERR_QUANT_MANY_COLORS, MAXJSAMPLE+1);
842
843  /* Create the colormap and color index table. */
844  create_colormap(cinfo);
845  create_colorindex(cinfo);
846
847  /* Allocate Floyd-Steinberg workspace now if requested.
848   * We do this now since it is FAR storage and may affect the memory
849   * manager's space calculations.  If the user changes to FS dither
850   * mode in a later pass, we will allocate the space then, and will
851   * possibly overrun the max_memory_to_use setting.
852   */
853  if (cinfo->dither_mode == JDITHER_FS)
854    alloc_fs_workspace(cinfo);
855}
856
857#endif /* QUANT_1PASS_SUPPORTED */
Note: See TracBrowser for help on using the repository browser.