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Created: 2024-01-20 12:28

/src/libjpeg-turbo.main/jquant1.c
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/*
2
 * jquant1.c
3
 *
4
 * This file was part of the Independent JPEG Group's software:
5
 * Copyright (C) 1991-1996, Thomas G. Lane.
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 * libjpeg-turbo Modifications:
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 * Copyright (C) 2009, 2015, 2022, D. R. Commander.
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 * For conditions of distribution and use, see the accompanying README.ijg
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 * file.
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 *
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 * This file contains 1-pass color quantization (color mapping) routines.
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 * These routines provide mapping to a fixed color map using equally spaced
13
 * color values.  Optional Floyd-Steinberg or ordered dithering is available.
14
 */
15
16
#define JPEG_INTERNALS
17
#include "jinclude.h"
18
#include "jpeglib.h"
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#include "jsamplecomp.h"
20
21
#if defined(QUANT_1PASS_SUPPORTED) && \
22
    (BITS_IN_JSAMPLE != 16 || defined(D_LOSSLESS_SUPPORTED))
23
24
25
/*
26
 * The main purpose of 1-pass quantization is to provide a fast, if not very
27
 * high quality, colormapped output capability.  A 2-pass quantizer usually
28
 * gives better visual quality; however, for quantized grayscale output this
29
 * quantizer is perfectly adequate.  Dithering is highly recommended with this
30
 * quantizer, though you can turn it off if you really want to.
31
 *
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 * In 1-pass quantization the colormap must be chosen in advance of seeing the
33
 * image.  We use a map consisting of all combinations of Ncolors[i] color
34
 * values for the i'th component.  The Ncolors[] values are chosen so that
35
 * their product, the total number of colors, is no more than that requested.
36
 * (In most cases, the product will be somewhat less.)
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 *
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 * Since the colormap is orthogonal, the representative value for each color
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 * component can be determined without considering the other components;
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 * then these indexes can be combined into a colormap index by a standard
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 * N-dimensional-array-subscript calculation.  Most of the arithmetic involved
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 * can be precalculated and stored in the lookup table colorindex[].
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 * colorindex[i][j] maps pixel value j in component i to the nearest
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 * representative value (grid plane) for that component; this index is
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 * multiplied by the array stride for component i, so that the
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 * index of the colormap entry closest to a given pixel value is just
47
 *    sum( colorindex[component-number][pixel-component-value] )
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 * Aside from being fast, this scheme allows for variable spacing between
49
 * representative values with no additional lookup cost.
50
 *
51
 * If gamma correction has been applied in color conversion, it might be wise
52
 * to adjust the color grid spacing so that the representative colors are
53
 * equidistant in linear space.  At this writing, gamma correction is not
54
 * implemented by jdcolor, so nothing is done here.
55
 */
56
57
58
/* Declarations for ordered dithering.
59
 *
60
 * We use a standard 16x16 ordered dither array.  The basic concept of ordered
61
 * dithering is described in many references, for instance Dale Schumacher's
62
 * chapter II.2 of Graphics Gems II (James Arvo, ed. Academic Press, 1991).
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 * In place of Schumacher's comparisons against a "threshold" value, we add a
64
 * "dither" value to the input pixel and then round the result to the nearest
65
 * output value.  The dither value is equivalent to (0.5 - threshold) times
66
 * the distance between output values.  For ordered dithering, we assume that
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 * the output colors are equally spaced; if not, results will probably be
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 * worse, since the dither may be too much or too little at a given point.
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 *
70
 * The normal calculation would be to form pixel value + dither, range-limit
71
 * this to 0.._MAXJSAMPLE, and then index into the colorindex table as usual.
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 * We can skip the separate range-limiting step by extending the colorindex
73
 * table in both directions.
74
 */
75
76
0
#define ODITHER_SIZE  16        /* dimension of dither matrix */
77
/* NB: if ODITHER_SIZE is not a power of 2, ODITHER_MASK uses will break */
78
0
#define ODITHER_CELLS  (ODITHER_SIZE * ODITHER_SIZE) /* # cells in matrix */
79
0
#define ODITHER_MASK  (ODITHER_SIZE - 1) /* mask for wrapping around
80
                                            counters */
81
82
typedef int ODITHER_MATRIX[ODITHER_SIZE][ODITHER_SIZE];
83
typedef int (*ODITHER_MATRIX_PTR)[ODITHER_SIZE];
84
85
static const UINT8 base_dither_matrix[ODITHER_SIZE][ODITHER_SIZE] = {
86
  /* Bayer's order-4 dither array.  Generated by the code given in
87
   * Stephen Hawley's article "Ordered Dithering" in Graphics Gems I.
88
   * The values in this array must range from 0 to ODITHER_CELLS-1.
89
   */
90
  {   0,192, 48,240, 12,204, 60,252,  3,195, 51,243, 15,207, 63,255 },
91
  { 128, 64,176,112,140, 76,188,124,131, 67,179,115,143, 79,191,127 },
92
  {  32,224, 16,208, 44,236, 28,220, 35,227, 19,211, 47,239, 31,223 },
93
  { 160, 96,144, 80,172,108,156, 92,163, 99,147, 83,175,111,159, 95 },
94
  {   8,200, 56,248,  4,196, 52,244, 11,203, 59,251,  7,199, 55,247 },
95
  { 136, 72,184,120,132, 68,180,116,139, 75,187,123,135, 71,183,119 },
96
  {  40,232, 24,216, 36,228, 20,212, 43,235, 27,219, 39,231, 23,215 },
97
  { 168,104,152, 88,164,100,148, 84,171,107,155, 91,167,103,151, 87 },
98
  {   2,194, 50,242, 14,206, 62,254,  1,193, 49,241, 13,205, 61,253 },
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  { 130, 66,178,114,142, 78,190,126,129, 65,177,113,141, 77,189,125 },
100
  {  34,226, 18,210, 46,238, 30,222, 33,225, 17,209, 45,237, 29,221 },
101
  { 162, 98,146, 82,174,110,158, 94,161, 97,145, 81,173,109,157, 93 },
102
  {  10,202, 58,250,  6,198, 54,246,  9,201, 57,249,  5,197, 53,245 },
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  { 138, 74,186,122,134, 70,182,118,137, 73,185,121,133, 69,181,117 },
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  {  42,234, 26,218, 38,230, 22,214, 41,233, 25,217, 37,229, 21,213 },
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  { 170,106,154, 90,166,102,150, 86,169,105,153, 89,165,101,149, 85 }
106
};
107
108
109
/* Declarations for Floyd-Steinberg dithering.
110
 *
111
 * Errors are accumulated into the array fserrors[], at a resolution of
112
 * 1/16th of a pixel count.  The error at a given pixel is propagated
113
 * to its not-yet-processed neighbors using the standard F-S fractions,
114
 *              ...     (here)  7/16
115
 *              3/16    5/16    1/16
116
 * We work left-to-right on even rows, right-to-left on odd rows.
117
 *
118
 * We can get away with a single array (holding one row's worth of errors)
119
 * by using it to store the current row's errors at pixel columns not yet
120
 * processed, but the next row's errors at columns already processed.  We
121
 * need only a few extra variables to hold the errors immediately around the
122
 * current column.  (If we are lucky, those variables are in registers, but
123
 * even if not, they're probably cheaper to access than array elements are.)
124
 *
125
 * The fserrors[] array is indexed [component#][position].
126
 * We provide (#columns + 2) entries per component; the extra entry at each
127
 * end saves us from special-casing the first and last pixels.
128
 */
129
130
#if BITS_IN_JSAMPLE == 8
131
typedef INT16 FSERROR;          /* 16 bits should be enough */
132
typedef int LOCFSERROR;         /* use 'int' for calculation temps */
133
#else
134
typedef JLONG FSERROR;          /* may need more than 16 bits */
135
typedef JLONG LOCFSERROR;       /* be sure calculation temps are big enough */
136
#endif
137
138
typedef FSERROR *FSERRPTR;      /* pointer to error array */
139
140
141
/* Private subobject */
142
143
0
#define MAX_Q_COMPS  4          /* max components I can handle */
144
145
typedef struct {
146
  struct jpeg_color_quantizer pub; /* public fields */
147
148
  /* Initially allocated colormap is saved here */
149
  _JSAMPARRAY sv_colormap;      /* The color map as a 2-D pixel array */
150
  int sv_actual;                /* number of entries in use */
151
152
  _JSAMPARRAY colorindex;       /* Precomputed mapping for speed */
153
  /* colorindex[i][j] = index of color closest to pixel value j in component i,
154
   * premultiplied as described above.  Since colormap indexes must fit into
155
   * _JSAMPLEs, the entries of this array will too.
156
   */
157
  boolean is_padded;            /* is the colorindex padded for odither? */
158
159
  int Ncolors[MAX_Q_COMPS];     /* # of values allocated to each component */
160
161
  /* Variables for ordered dithering */
162
  int row_index;                /* cur row's vertical index in dither matrix */
163
  ODITHER_MATRIX_PTR odither[MAX_Q_COMPS]; /* one dither array per component */
164
165
  /* Variables for Floyd-Steinberg dithering */
166
  FSERRPTR fserrors[MAX_Q_COMPS]; /* accumulated errors */
167
  boolean on_odd_row;           /* flag to remember which row we are on */
168
} my_cquantizer;
169
170
typedef my_cquantizer *my_cquantize_ptr;
171
172
173
/*
174
 * Policy-making subroutines for create_colormap and create_colorindex.
175
 * These routines determine the colormap to be used.  The rest of the module
176
 * only assumes that the colormap is orthogonal.
177
 *
178
 *  * select_ncolors decides how to divvy up the available colors
179
 *    among the components.
180
 *  * output_value defines the set of representative values for a component.
181
 *  * largest_input_value defines the mapping from input values to
182
 *    representative values for a component.
183
 * Note that the latter two routines may impose different policies for
184
 * different components, though this is not currently done.
185
 */
186
187
188
LOCAL(int)
189
select_ncolors(j_decompress_ptr cinfo, int Ncolors[])
190
/* Determine allocation of desired colors to components, */
191
/* and fill in Ncolors[] array to indicate choice. */
192
/* Return value is total number of colors (product of Ncolors[] values). */
193
0
{
194
0
  int nc = cinfo->out_color_components; /* number of color components */
195
0
  int max_colors = cinfo->desired_number_of_colors;
196
0
  int total_colors, iroot, i, j;
197
0
  boolean changed;
198
0
  long temp;
199
0
  int RGB_order[3] = { RGB_GREEN, RGB_RED, RGB_BLUE };
200
0
  RGB_order[0] = rgb_green[cinfo->out_color_space];
201
0
  RGB_order[1] = rgb_red[cinfo->out_color_space];
202
0
  RGB_order[2] = rgb_blue[cinfo->out_color_space];
203
204
  /* We can allocate at least the nc'th root of max_colors per component. */
205
  /* Compute floor(nc'th root of max_colors). */
206
0
  iroot = 1;
207
0
  do {
208
0
    iroot++;
209
0
    temp = iroot;               /* set temp = iroot ** nc */
210
0
    for (i = 1; i < nc; i++)
211
0
      temp *= iroot;
212
0
  } while (temp <= (long)max_colors); /* repeat till iroot exceeds root */
213
0
  iroot--;                      /* now iroot = floor(root) */
214
215
  /* Must have at least 2 color values per component */
216
0
  if (iroot < 2)
217
0
    ERREXIT1(cinfo, JERR_QUANT_FEW_COLORS, (int)temp);
218
219
  /* Initialize to iroot color values for each component */
220
0
  total_colors = 1;
221
0
  for (i = 0; i < nc; i++) {
222
0
    Ncolors[i] = iroot;
223
0
    total_colors *= iroot;
224
0
  }
225
  /* We may be able to increment the count for one or more components without
226
   * exceeding max_colors, though we know not all can be incremented.
227
   * Sometimes, the first component can be incremented more than once!
228
   * (Example: for 16 colors, we start at 2*2*2, go to 3*2*2, then 4*2*2.)
229
   * In RGB colorspace, try to increment G first, then R, then B.
230
   */
231
0
  do {
232
0
    changed = FALSE;
233
0
    for (i = 0; i < nc; i++) {
234
0
      j = (cinfo->out_color_space == JCS_RGB ? RGB_order[i] : i);
235
      /* calculate new total_colors if Ncolors[j] is incremented */
236
0
      temp = total_colors / Ncolors[j];
237
0
      temp *= Ncolors[j] + 1;   /* done in long arith to avoid oflo */
238
0
      if (temp > (long)max_colors)
239
0
        break;                  /* won't fit, done with this pass */
240
0
      Ncolors[j]++;             /* OK, apply the increment */
241
0
      total_colors = (int)temp;
242
0
      changed = TRUE;
243
0
    }
244
0
  } while (changed);
245
246
0
  return total_colors;
247
0
}
248
249
250
LOCAL(int)
251
output_value(j_decompress_ptr cinfo, int ci, int j, int maxj)
252
/* Return j'th output value, where j will range from 0 to maxj */
253
/* The output values must fall in 0.._MAXJSAMPLE in increasing order */
254
0
{
255
  /* We always provide values 0 and _MAXJSAMPLE for each component;
256
   * any additional values are equally spaced between these limits.
257
   * (Forcing the upper and lower values to the limits ensures that
258
   * dithering can't produce a color outside the selected gamut.)
259
   */
260
0
  return (int)(((JLONG)j * _MAXJSAMPLE + maxj / 2) / maxj);
261
0
}
262
263
264
LOCAL(int)
265
largest_input_value(j_decompress_ptr cinfo, int ci, int j, int maxj)
266
/* Return largest input value that should map to j'th output value */
267
/* Must have largest(j=0) >= 0, and largest(j=maxj) >= _MAXJSAMPLE */
268
0
{
269
  /* Breakpoints are halfway between values returned by output_value */
270
0
  return (int)(((JLONG)(2 * j + 1) * _MAXJSAMPLE + maxj) / (2 * maxj));
271
0
}
272
273
274
/*
275
 * Create the colormap.
276
 */
277
278
LOCAL(void)
279
create_colormap(j_decompress_ptr cinfo)
280
0
{
281
0
  my_cquantize_ptr cquantize = (my_cquantize_ptr)cinfo->cquantize;
282
0
  _JSAMPARRAY colormap;         /* Created colormap */
283
0
  int total_colors;             /* Number of distinct output colors */
284
0
  int i, j, k, nci, blksize, blkdist, ptr, val;
285
286
  /* Select number of colors for each component */
287
0
  total_colors = select_ncolors(cinfo, cquantize->Ncolors);
288
289
  /* Report selected color counts */
290
0
  if (cinfo->out_color_components == 3)
291
0
    TRACEMS4(cinfo, 1, JTRC_QUANT_3_NCOLORS, total_colors,
292
0
             cquantize->Ncolors[0], cquantize->Ncolors[1],
293
0
             cquantize->Ncolors[2]);
294
0
  else
295
0
    TRACEMS1(cinfo, 1, JTRC_QUANT_NCOLORS, total_colors);
296
297
  /* Allocate and fill in the colormap. */
298
  /* The colors are ordered in the map in standard row-major order, */
299
  /* i.e. rightmost (highest-indexed) color changes most rapidly. */
300
301
0
  colormap = (_JSAMPARRAY)(*cinfo->mem->alloc_sarray)
302
0
    ((j_common_ptr)cinfo, JPOOL_IMAGE,
303
0
     (JDIMENSION)total_colors, (JDIMENSION)cinfo->out_color_components);
304
305
  /* blksize is number of adjacent repeated entries for a component */
306
  /* blkdist is distance between groups of identical entries for a component */
307
0
  blkdist = total_colors;
308
309
0
  for (i = 0; i < cinfo->out_color_components; i++) {
310
    /* fill in colormap entries for i'th color component */
311
0
    nci = cquantize->Ncolors[i]; /* # of distinct values for this color */
312
0
    blksize = blkdist / nci;
313
0
    for (j = 0; j < nci; j++) {
314
      /* Compute j'th output value (out of nci) for component */
315
0
      val = output_value(cinfo, i, j, nci - 1);
316
      /* Fill in all colormap entries that have this value of this component */
317
0
      for (ptr = j * blksize; ptr < total_colors; ptr += blkdist) {
318
        /* fill in blksize entries beginning at ptr */
319
0
        for (k = 0; k < blksize; k++)
320
0
          colormap[i][ptr + k] = (_JSAMPLE)val;
321
0
      }
322
0
    }
323
0
    blkdist = blksize;          /* blksize of this color is blkdist of next */
324
0
  }
325
326
  /* Save the colormap in private storage,
327
   * where it will survive color quantization mode changes.
328
   */
329
0
  cquantize->sv_colormap = colormap;
330
0
  cquantize->sv_actual = total_colors;
331
0
}
332
333
334
/*
335
 * Create the color index table.
336
 */
337
338
LOCAL(void)
339
create_colorindex(j_decompress_ptr cinfo)
340
0
{
341
0
  my_cquantize_ptr cquantize = (my_cquantize_ptr)cinfo->cquantize;
342
0
  _JSAMPROW indexptr;
343
0
  int i, j, k, nci, blksize, val, pad;
344
345
  /* For ordered dither, we pad the color index tables by _MAXJSAMPLE in
346
   * each direction (input index values can be -_MAXJSAMPLE .. 2*_MAXJSAMPLE).
347
   * This is not necessary in the other dithering modes.  However, we
348
   * flag whether it was done in case user changes dithering mode.
349
   */
350
0
  if (cinfo->dither_mode == JDITHER_ORDERED) {
351
0
    pad = _MAXJSAMPLE * 2;
352
0
    cquantize->is_padded = TRUE;
353
0
  } else {
354
0
    pad = 0;
355
0
    cquantize->is_padded = FALSE;
356
0
  }
357
358
0
  cquantize->colorindex = (_JSAMPARRAY)(*cinfo->mem->alloc_sarray)
359
0
    ((j_common_ptr)cinfo, JPOOL_IMAGE,
360
0
     (JDIMENSION)(_MAXJSAMPLE + 1 + pad),
361
0
     (JDIMENSION)cinfo->out_color_components);
362
363
  /* blksize is number of adjacent repeated entries for a component */
364
0
  blksize = cquantize->sv_actual;
365
366
0
  for (i = 0; i < cinfo->out_color_components; i++) {
367
    /* fill in colorindex entries for i'th color component */
368
0
    nci = cquantize->Ncolors[i]; /* # of distinct values for this color */
369
0
    blksize = blksize / nci;
370
371
    /* adjust colorindex pointers to provide padding at negative indexes. */
372
0
    if (pad)
373
0
      cquantize->colorindex[i] += _MAXJSAMPLE;
374
375
    /* in loop, val = index of current output value, */
376
    /* and k = largest j that maps to current val */
377
0
    indexptr = cquantize->colorindex[i];
378
0
    val = 0;
379
0
    k = largest_input_value(cinfo, i, 0, nci - 1);
380
0
    for (j = 0; j <= _MAXJSAMPLE; j++) {
381
0
      while (j > k)             /* advance val if past boundary */
382
0
        k = largest_input_value(cinfo, i, ++val, nci - 1);
383
      /* premultiply so that no multiplication needed in main processing */
384
0
      indexptr[j] = (_JSAMPLE)(val * blksize);
385
0
    }
386
    /* Pad at both ends if necessary */
387
0
    if (pad)
388
0
      for (j = 1; j <= _MAXJSAMPLE; j++) {
389
0
        indexptr[-j] = indexptr[0];
390
0
        indexptr[_MAXJSAMPLE + j] = indexptr[_MAXJSAMPLE];
391
0
      }
392
0
  }
393
0
}
394
395
396
/*
397
 * Create an ordered-dither array for a component having ncolors
398
 * distinct output values.
399
 */
400
401
LOCAL(ODITHER_MATRIX_PTR)
402
make_odither_array(j_decompress_ptr cinfo, int ncolors)
403
0
{
404
0
  ODITHER_MATRIX_PTR odither;
405
0
  int j, k;
406
0
  JLONG num, den;
407
408
0
  odither = (ODITHER_MATRIX_PTR)
409
0
    (*cinfo->mem->alloc_small) ((j_common_ptr)cinfo, JPOOL_IMAGE,
410
0
                                sizeof(ODITHER_MATRIX));
411
  /* The inter-value distance for this color is _MAXJSAMPLE/(ncolors-1).
412
   * Hence the dither value for the matrix cell with fill order f
413
   * (f=0..N-1) should be (N-1-2*f)/(2*N) * _MAXJSAMPLE/(ncolors-1).
414
   * On 16-bit-int machine, be careful to avoid overflow.
415
   */
416
0
  den = 2 * ODITHER_CELLS * ((JLONG)(ncolors - 1));
417
0
  for (j = 0; j < ODITHER_SIZE; j++) {
418
0
    for (k = 0; k < ODITHER_SIZE; k++) {
419
0
      num = ((JLONG)(ODITHER_CELLS - 1 -
420
0
                     2 * ((int)base_dither_matrix[j][k]))) * _MAXJSAMPLE;
421
      /* Ensure round towards zero despite C's lack of consistency
422
       * about rounding negative values in integer division...
423
       */
424
0
      odither[j][k] = (int)(num < 0 ? -((-num) / den) : num / den);
425
0
    }
426
0
  }
427
0
  return odither;
428
0
}
429
430
431
/*
432
 * Create the ordered-dither tables.
433
 * Components having the same number of representative colors may
434
 * share a dither table.
435
 */
436
437
LOCAL(void)
438
create_odither_tables(j_decompress_ptr cinfo)
439
0
{
440
0
  my_cquantize_ptr cquantize = (my_cquantize_ptr)cinfo->cquantize;
441
0
  ODITHER_MATRIX_PTR odither;
442
0
  int i, j, nci;
443
444
0
  for (i = 0; i < cinfo->out_color_components; i++) {
445
0
    nci = cquantize->Ncolors[i]; /* # of distinct values for this color */
446
0
    odither = NULL;             /* search for matching prior component */
447
0
    for (j = 0; j < i; j++) {
448
0
      if (nci == cquantize->Ncolors[j]) {
449
0
        odither = cquantize->odither[j];
450
0
        break;
451
0
      }
452
0
    }
453
0
    if (odither == NULL)        /* need a new table? */
454
0
      odither = make_odither_array(cinfo, nci);
455
0
    cquantize->odither[i] = odither;
456
0
  }
457
0
}
458
459
460
/*
461
 * Map some rows of pixels to the output colormapped representation.
462
 */
463
464
METHODDEF(void)
465
color_quantize(j_decompress_ptr cinfo, _JSAMPARRAY input_buf,
466
               _JSAMPARRAY output_buf, int num_rows)
467
/* General case, no dithering */
468
0
{
469
0
  my_cquantize_ptr cquantize = (my_cquantize_ptr)cinfo->cquantize;
470
0
  _JSAMPARRAY colorindex = cquantize->colorindex;
471
0
  register int pixcode, ci;
472
0
  register _JSAMPROW ptrin, ptrout;
473
0
  int row;
474
0
  JDIMENSION col;
475
0
  JDIMENSION width = cinfo->output_width;
476
0
  register int nc = cinfo->out_color_components;
477
478
0
  for (row = 0; row < num_rows; row++) {
479
0
    ptrin = input_buf[row];
480
0
    ptrout = output_buf[row];
481
0
    for (col = width; col > 0; col--) {
482
0
      pixcode = 0;
483
0
      for (ci = 0; ci < nc; ci++) {
484
0
        pixcode += colorindex[ci][*ptrin++];
485
0
      }
486
0
      *ptrout++ = (_JSAMPLE)pixcode;
487
0
    }
488
0
  }
489
0
}
490
491
492
METHODDEF(void)
493
color_quantize3(j_decompress_ptr cinfo, _JSAMPARRAY input_buf,
494
                _JSAMPARRAY output_buf, int num_rows)
495
/* Fast path for out_color_components==3, no dithering */
496
0
{
497
0
  my_cquantize_ptr cquantize = (my_cquantize_ptr)cinfo->cquantize;
498
0
  register int pixcode;
499
0
  register _JSAMPROW ptrin, ptrout;
500
0
  _JSAMPROW colorindex0 = cquantize->colorindex[0];
501
0
  _JSAMPROW colorindex1 = cquantize->colorindex[1];
502
0
  _JSAMPROW colorindex2 = cquantize->colorindex[2];
503
0
  int row;
504
0
  JDIMENSION col;
505
0
  JDIMENSION width = cinfo->output_width;
506
507
0
  for (row = 0; row < num_rows; row++) {
508
0
    ptrin = input_buf[row];
509
0
    ptrout = output_buf[row];
510
0
    for (col = width; col > 0; col--) {
511
0
      pixcode  = colorindex0[*ptrin++];
512
0
      pixcode += colorindex1[*ptrin++];
513
0
      pixcode += colorindex2[*ptrin++];
514
0
      *ptrout++ = (_JSAMPLE)pixcode;
515
0
    }
516
0
  }
517
0
}
518
519
520
METHODDEF(void)
521
quantize_ord_dither(j_decompress_ptr cinfo, _JSAMPARRAY input_buf,
522
                    _JSAMPARRAY output_buf, int num_rows)
523
/* General case, with ordered dithering */
524
0
{
525
0
  my_cquantize_ptr cquantize = (my_cquantize_ptr)cinfo->cquantize;
526
0
  register _JSAMPROW input_ptr;
527
0
  register _JSAMPROW output_ptr;
528
0
  _JSAMPROW colorindex_ci;
529
0
  int *dither;                  /* points to active row of dither matrix */
530
0
  int row_index, col_index;     /* current indexes into dither matrix */
531
0
  int nc = cinfo->out_color_components;
532
0
  int ci;
533
0
  int row;
534
0
  JDIMENSION col;
535
0
  JDIMENSION width = cinfo->output_width;
536
537
0
  for (row = 0; row < num_rows; row++) {
538
    /* Initialize output values to 0 so can process components separately */
539
0
    jzero_far((void *)output_buf[row], (size_t)(width * sizeof(_JSAMPLE)));
540
0
    row_index = cquantize->row_index;
541
0
    for (ci = 0; ci < nc; ci++) {
542
0
      input_ptr = input_buf[row] + ci;
543
0
      output_ptr = output_buf[row];
544
0
      colorindex_ci = cquantize->colorindex[ci];
545
0
      dither = cquantize->odither[ci][row_index];
546
0
      col_index = 0;
547
548
0
      for (col = width; col > 0; col--) {
549
        /* Form pixel value + dither, range-limit to 0.._MAXJSAMPLE,
550
         * select output value, accumulate into output code for this pixel.
551
         * Range-limiting need not be done explicitly, as we have extended
552
         * the colorindex table to produce the right answers for out-of-range
553
         * inputs.  The maximum dither is +- _MAXJSAMPLE; this sets the
554
         * required amount of padding.
555
         */
556
0
        *output_ptr +=
557
0
          colorindex_ci[*input_ptr + dither[col_index]];
558
0
        input_ptr += nc;
559
0
        output_ptr++;
560
0
        col_index = (col_index + 1) & ODITHER_MASK;
561
0
      }
562
0
    }
563
    /* Advance row index for next row */
564
0
    row_index = (row_index + 1) & ODITHER_MASK;
565
0
    cquantize->row_index = row_index;
566
0
  }
567
0
}
568
569
570
METHODDEF(void)
571
quantize3_ord_dither(j_decompress_ptr cinfo, _JSAMPARRAY input_buf,
572
                     _JSAMPARRAY output_buf, int num_rows)
573
/* Fast path for out_color_components==3, with ordered dithering */
574
0
{
575
0
  my_cquantize_ptr cquantize = (my_cquantize_ptr)cinfo->cquantize;
576
0
  register int pixcode;
577
0
  register _JSAMPROW input_ptr;
578
0
  register _JSAMPROW output_ptr;
579
0
  _JSAMPROW colorindex0 = cquantize->colorindex[0];
580
0
  _JSAMPROW colorindex1 = cquantize->colorindex[1];
581
0
  _JSAMPROW colorindex2 = cquantize->colorindex[2];
582
0
  int *dither0;                 /* points to active row of dither matrix */
583
0
  int *dither1;
584
0
  int *dither2;
585
0
  int row_index, col_index;     /* current indexes into dither matrix */
586
0
  int row;
587
0
  JDIMENSION col;
588
0
  JDIMENSION width = cinfo->output_width;
589
590
0
  for (row = 0; row < num_rows; row++) {
591
0
    row_index = cquantize->row_index;
592
0
    input_ptr = input_buf[row];
593
0
    output_ptr = output_buf[row];
594
0
    dither0 = cquantize->odither[0][row_index];
595
0
    dither1 = cquantize->odither[1][row_index];
596
0
    dither2 = cquantize->odither[2][row_index];
597
0
    col_index = 0;
598
599
0
    for (col = width; col > 0; col--) {
600
0
      pixcode  = colorindex0[(*input_ptr++) + dither0[col_index]];
601
0
      pixcode += colorindex1[(*input_ptr++) + dither1[col_index]];
602
0
      pixcode += colorindex2[(*input_ptr++) + dither2[col_index]];
603
0
      *output_ptr++ = (_JSAMPLE)pixcode;
604
0
      col_index = (col_index + 1) & ODITHER_MASK;
605
0
    }
606
0
    row_index = (row_index + 1) & ODITHER_MASK;
607
0
    cquantize->row_index = row_index;
608
0
  }
609
0
}
610
611
612
METHODDEF(void)
613
quantize_fs_dither(j_decompress_ptr cinfo, _JSAMPARRAY input_buf,
614
                   _JSAMPARRAY output_buf, int num_rows)
615
/* General case, with Floyd-Steinberg dithering */
616
0
{
617
0
  my_cquantize_ptr cquantize = (my_cquantize_ptr)cinfo->cquantize;
618
0
  register LOCFSERROR cur;      /* current error or pixel value */
619
0
  LOCFSERROR belowerr;          /* error for pixel below cur */
620
0
  LOCFSERROR bpreverr;          /* error for below/prev col */
621
0
  LOCFSERROR bnexterr;          /* error for below/next col */
622
0
  LOCFSERROR delta;
623
0
  register FSERRPTR errorptr;   /* => fserrors[] at column before current */
624
0
  register _JSAMPROW input_ptr;
625
0
  register _JSAMPROW output_ptr;
626
0
  _JSAMPROW colorindex_ci;
627
0
  _JSAMPROW colormap_ci;
628
0
  int pixcode;
629
0
  int nc = cinfo->out_color_components;
630
0
  int dir;                      /* 1 for left-to-right, -1 for right-to-left */
631
0
  int dirnc;                    /* dir * nc */
632
0
  int ci;
633
0
  int row;
634
0
  JDIMENSION col;
635
0
  JDIMENSION width = cinfo->output_width;
636
0
  _JSAMPLE *range_limit = (_JSAMPLE *)cinfo->sample_range_limit;
637
0
  SHIFT_TEMPS
638
639
0
  for (row = 0; row < num_rows; row++) {
640
    /* Initialize output values to 0 so can process components separately */
641
0
    jzero_far((void *)output_buf[row], (size_t)(width * sizeof(_JSAMPLE)));
642
0
    for (ci = 0; ci < nc; ci++) {
643
0
      input_ptr = input_buf[row] + ci;
644
0
      output_ptr = output_buf[row];
645
0
      if (cquantize->on_odd_row) {
646
        /* work right to left in this row */
647
0
        input_ptr += (width - 1) * nc; /* so point to rightmost pixel */
648
0
        output_ptr += width - 1;
649
0
        dir = -1;
650
0
        dirnc = -nc;
651
0
        errorptr = cquantize->fserrors[ci] + (width + 1); /* => entry after last column */
652
0
      } else {
653
        /* work left to right in this row */
654
0
        dir = 1;
655
0
        dirnc = nc;
656
0
        errorptr = cquantize->fserrors[ci]; /* => entry before first column */
657
0
      }
658
0
      colorindex_ci = cquantize->colorindex[ci];
659
0
      colormap_ci = cquantize->sv_colormap[ci];
660
      /* Preset error values: no error propagated to first pixel from left */
661
0
      cur = 0;
662
      /* and no error propagated to row below yet */
663
0
      belowerr = bpreverr = 0;
664
665
0
      for (col = width; col > 0; col--) {
666
        /* cur holds the error propagated from the previous pixel on the
667
         * current line.  Add the error propagated from the previous line
668
         * to form the complete error correction term for this pixel, and
669
         * round the error term (which is expressed * 16) to an integer.
670
         * RIGHT_SHIFT rounds towards minus infinity, so adding 8 is correct
671
         * for either sign of the error value.
672
         * Note: errorptr points to *previous* column's array entry.
673
         */
674
0
        cur = RIGHT_SHIFT(cur + errorptr[dir] + 8, 4);
675
        /* Form pixel value + error, and range-limit to 0.._MAXJSAMPLE.
676
         * The maximum error is +- _MAXJSAMPLE; this sets the required size
677
         * of the range_limit array.
678
         */
679
0
        cur += *input_ptr;
680
0
        cur = range_limit[cur];
681
        /* Select output value, accumulate into output code for this pixel */
682
0
        pixcode = colorindex_ci[cur];
683
0
        *output_ptr += (_JSAMPLE)pixcode;
684
        /* Compute actual representation error at this pixel */
685
        /* Note: we can do this even though we don't have the final */
686
        /* pixel code, because the colormap is orthogonal. */
687
0
        cur -= colormap_ci[pixcode];
688
        /* Compute error fractions to be propagated to adjacent pixels.
689
         * Add these into the running sums, and simultaneously shift the
690
         * next-line error sums left by 1 column.
691
         */
692
0
        bnexterr = cur;
693
0
        delta = cur * 2;
694
0
        cur += delta;           /* form error * 3 */
695
0
        errorptr[0] = (FSERROR)(bpreverr + cur);
696
0
        cur += delta;           /* form error * 5 */
697
0
        bpreverr = belowerr + cur;
698
0
        belowerr = bnexterr;
699
0
        cur += delta;           /* form error * 7 */
700
        /* At this point cur contains the 7/16 error value to be propagated
701
         * to the next pixel on the current line, and all the errors for the
702
         * next line have been shifted over. We are therefore ready to move on.
703
         */
704
0
        input_ptr += dirnc;     /* advance input ptr to next column */
705
0
        output_ptr += dir;      /* advance output ptr to next column */
706
0
        errorptr += dir;        /* advance errorptr to current column */
707
0
      }
708
      /* Post-loop cleanup: we must unload the final error value into the
709
       * final fserrors[] entry.  Note we need not unload belowerr because
710
       * it is for the dummy column before or after the actual array.
711
       */
712
0
      errorptr[0] = (FSERROR)bpreverr; /* unload prev err into array */
713
0
    }
714
0
    cquantize->on_odd_row = (cquantize->on_odd_row ? FALSE : TRUE);
715
0
  }
716
0
}
717
718
719
/*
720
 * Allocate workspace for Floyd-Steinberg errors.
721
 */
722
723
LOCAL(void)
724
alloc_fs_workspace(j_decompress_ptr cinfo)
725
0
{
726
0
  my_cquantize_ptr cquantize = (my_cquantize_ptr)cinfo->cquantize;
727
0
  size_t arraysize;
728
0
  int i;
729
730
0
  arraysize = (size_t)((cinfo->output_width + 2) * sizeof(FSERROR));
731
0
  for (i = 0; i < cinfo->out_color_components; i++) {
732
0
    cquantize->fserrors[i] = (FSERRPTR)
733
0
      (*cinfo->mem->alloc_large) ((j_common_ptr)cinfo, JPOOL_IMAGE, arraysize);
734
0
  }
735
0
}
736
737
738
/*
739
 * Initialize for one-pass color quantization.
740
 */
741
742
METHODDEF(void)
743
start_pass_1_quant(j_decompress_ptr cinfo, boolean is_pre_scan)
744
0
{
745
0
  my_cquantize_ptr cquantize = (my_cquantize_ptr)cinfo->cquantize;
746
0
  size_t arraysize;
747
0
  int i;
748
749
  /* Install my colormap. */
750
0
  cinfo->colormap = (JSAMPARRAY)cquantize->sv_colormap;
751
0
  cinfo->actual_number_of_colors = cquantize->sv_actual;
752
753
  /* Initialize for desired dithering mode. */
754
0
  switch (cinfo->dither_mode) {
755
0
  case JDITHER_NONE:
756
0
    if (cinfo->out_color_components == 3)
757
0
      cquantize->pub._color_quantize = color_quantize3;
758
0
    else
759
0
      cquantize->pub._color_quantize = color_quantize;
760
0
    break;
761
0
  case JDITHER_ORDERED:
762
0
    if (cinfo->out_color_components == 3)
763
0
      cquantize->pub._color_quantize = quantize3_ord_dither;
764
0
    else
765
0
      cquantize->pub._color_quantize = quantize_ord_dither;
766
0
    cquantize->row_index = 0;   /* initialize state for ordered dither */
767
    /* If user changed to ordered dither from another mode,
768
     * we must recreate the color index table with padding.
769
     * This will cost extra space, but probably isn't very likely.
770
     */
771
0
    if (!cquantize->is_padded)
772
0
      create_colorindex(cinfo);
773
    /* Create ordered-dither tables if we didn't already. */
774
0
    if (cquantize->odither[0] == NULL)
775
0
      create_odither_tables(cinfo);
776
0
    break;
777
0
  case JDITHER_FS:
778
0
    cquantize->pub._color_quantize = quantize_fs_dither;
779
0
    cquantize->on_odd_row = FALSE; /* initialize state for F-S dither */
780
    /* Allocate Floyd-Steinberg workspace if didn't already. */
781
0
    if (cquantize->fserrors[0] == NULL)
782
0
      alloc_fs_workspace(cinfo);
783
    /* Initialize the propagated errors to zero. */
784
0
    arraysize = (size_t)((cinfo->output_width + 2) * sizeof(FSERROR));
785
0
    for (i = 0; i < cinfo->out_color_components; i++)
786
0
      jzero_far((void *)cquantize->fserrors[i], arraysize);
787
0
    break;
788
0
  default:
789
0
    ERREXIT(cinfo, JERR_NOT_COMPILED);
790
0
    break;
791
0
  }
792
0
}
793
794
795
/*
796
 * Finish up at the end of the pass.
797
 */
798
799
METHODDEF(void)
800
finish_pass_1_quant(j_decompress_ptr cinfo)
801
0
{
802
  /* no work in 1-pass case */
803
0
}
804
805
806
/*
807
 * Switch to a new external colormap between output passes.
808
 * Shouldn't get to this module!
809
 */
810
811
METHODDEF(void)
812
new_color_map_1_quant(j_decompress_ptr cinfo)
813
0
{
814
0
  ERREXIT(cinfo, JERR_MODE_CHANGE);
815
0
}
816
817
818
/*
819
 * Module initialization routine for 1-pass color quantization.
820
 */
821
822
GLOBAL(void)
823
_jinit_1pass_quantizer(j_decompress_ptr cinfo)
824
0
{
825
0
  my_cquantize_ptr cquantize;
826
827
0
  if (cinfo->data_precision != BITS_IN_JSAMPLE)
828
0
    ERREXIT1(cinfo, JERR_BAD_PRECISION, cinfo->data_precision);
829
830
0
  cquantize = (my_cquantize_ptr)
831
0
    (*cinfo->mem->alloc_small) ((j_common_ptr)cinfo, JPOOL_IMAGE,
832
0
                                sizeof(my_cquantizer));
833
0
  cinfo->cquantize = (struct jpeg_color_quantizer *)cquantize;
834
0
  cquantize->pub.start_pass = start_pass_1_quant;
835
0
  cquantize->pub.finish_pass = finish_pass_1_quant;
836
0
  cquantize->pub.new_color_map = new_color_map_1_quant;
837
0
  cquantize->fserrors[0] = NULL; /* Flag FS workspace not allocated */
838
0
  cquantize->odither[0] = NULL; /* Also flag odither arrays not allocated */
839
840
  /* Make sure my internal arrays won't overflow */
841
0
  if (cinfo->out_color_components > MAX_Q_COMPS)
842
0
    ERREXIT1(cinfo, JERR_QUANT_COMPONENTS, MAX_Q_COMPS);
843
  /* Make sure colormap indexes can be represented by _JSAMPLEs */
844
0
  if (cinfo->desired_number_of_colors > (_MAXJSAMPLE + 1))
845
0
    ERREXIT1(cinfo, JERR_QUANT_MANY_COLORS, _MAXJSAMPLE + 1);
846
847
  /* Create the colormap and color index table. */
848
0
  create_colormap(cinfo);
849
0
  create_colorindex(cinfo);
850
851
  /* Allocate Floyd-Steinberg workspace now if requested.
852
   * We do this now since it may affect the memory manager's space
853
   * calculations.  If the user changes to FS dither mode in a later pass, we
854
   * will allocate the space then, and will possibly overrun the
855
   * max_memory_to_use setting.
856
   */
857
0
  if (cinfo->dither_mode == JDITHER_FS)
858
0
    alloc_fs_workspace(cinfo);
859
0
}
Unexecuted instantiation: j12init_1pass_quantizer
Unexecuted instantiation: j16init_1pass_quantizer
Unexecuted instantiation: jinit_1pass_quantizer
860
861
#endif /* defined(QUANT_1PASS_SUPPORTED) &&
862
          (BITS_IN_JSAMPLE != 16 || defined(D_LOSSLESS_SUPPORTED)) */