source: trunk/libjpeg/jquant1.c @ 426

Last change on this file since 426 was 15, checked in by Eugene Romanenko, 16 years ago

needed libs update

File size: 31.4 KB
Line 
1/*
2 * jquant1.c
3 *
4 * Copyright (C) 1991-1996, Thomas G. Lane.
5 * This file is part of the Independent JPEG Group's software.
6 * For conditions of distribution and use, see the accompanying README file.
7 *
8 * This file contains 1-pass color quantization (color mapping) routines.
9 * These routines provide mapping to a fixed color map using equally spaced
10 * color values.  Optional Floyd-Steinberg or ordered dithering is available.
11 */
12
13#define JPEG_INTERNALS
14#include "jinclude.h"
15#include "jpeglib.h"
16
17#ifdef QUANT_1PASS_SUPPORTED
18
19
20/*
21 * The main purpose of 1-pass quantization is to provide a fast, if not very
22 * high quality, colormapped output capability.  A 2-pass quantizer usually
23 * gives better visual quality; however, for quantized grayscale output this
24 * quantizer is perfectly adequate.  Dithering is highly recommended with this
25 * quantizer, though you can turn it off if you really want to.
26 *
27 * In 1-pass quantization the colormap must be chosen in advance of seeing the
28 * image.  We use a map consisting of all combinations of Ncolors[i] color
29 * values for the i'th component.  The Ncolors[] values are chosen so that
30 * their product, the total number of colors, is no more than that requested.
31 * (In most cases, the product will be somewhat less.)
32 *
33 * Since the colormap is orthogonal, the representative value for each color
34 * component can be determined without considering the other components;
35 * then these indexes can be combined into a colormap index by a standard
36 * N-dimensional-array-subscript calculation.  Most of the arithmetic involved
37 * can be precalculated and stored in the lookup table colorindex[].
38 * colorindex[i][j] maps pixel value j in component i to the nearest
39 * representative value (grid plane) for that component; this index is
40 * multiplied by the array stride for component i, so that the
41 * index of the colormap entry closest to a given pixel value is just
42 *    sum( colorindex[component-number][pixel-component-value] )
43 * Aside from being fast, this scheme allows for variable spacing between
44 * representative values with no additional lookup cost.
45 *
46 * If gamma correction has been applied in color conversion, it might be wise
47 * to adjust the color grid spacing so that the representative colors are
48 * equidistant in linear space.  At this writing, gamma correction is not
49 * implemented by jdcolor, so nothing is done here.
50 */
51
52
53/* Declarations for ordered dithering.
54 *
55 * We use a standard 16x16 ordered dither array.  The basic concept of ordered
56 * dithering is described in many references, for instance Dale Schumacher's
57 * chapter II.2 of Graphics Gems II (James Arvo, ed. Academic Press, 1991).
58 * In place of Schumacher's comparisons against a "threshold" value, we add a
59 * "dither" value to the input pixel and then round the result to the nearest
60 * output value.  The dither value is equivalent to (0.5 - threshold) times
61 * the distance between output values.  For ordered dithering, we assume that
62 * the output colors are equally spaced; if not, results will probably be
63 * worse, since the dither may be too much or too little at a given point.
64 *
65 * The normal calculation would be to form pixel value + dither, range-limit
66 * this to 0..MAXJSAMPLE, and then index into the colorindex table as usual.
67 * We can skip the separate range-limiting step by extending the colorindex
68 * table in both directions.
69 */
70
71#define ODITHER_SIZE  16        /* dimension of dither matrix */
72/* NB: if ODITHER_SIZE is not a power of 2, ODITHER_MASK uses will break */
73#define ODITHER_CELLS (ODITHER_SIZE*ODITHER_SIZE)       /* # cells in matrix */
74#define ODITHER_MASK  (ODITHER_SIZE-1) /* mask for wrapping around counters */
75
76typedef int ODITHER_MATRIX[ODITHER_SIZE][ODITHER_SIZE];
77typedef int (*ODITHER_MATRIX_PTR)[ODITHER_SIZE];
78
79static const UINT8 base_dither_matrix[ODITHER_SIZE][ODITHER_SIZE] = {
80  /* Bayer's order-4 dither array.  Generated by the code given in
81   * Stephen Hawley's article "Ordered Dithering" in Graphics Gems I.
82   * The values in this array must range from 0 to ODITHER_CELLS-1.
83   */
84  {   0,192, 48,240, 12,204, 60,252,  3,195, 51,243, 15,207, 63,255 },
85  { 128, 64,176,112,140, 76,188,124,131, 67,179,115,143, 79,191,127 },
86  {  32,224, 16,208, 44,236, 28,220, 35,227, 19,211, 47,239, 31,223 },
87  { 160, 96,144, 80,172,108,156, 92,163, 99,147, 83,175,111,159, 95 },
88  {   8,200, 56,248,  4,196, 52,244, 11,203, 59,251,  7,199, 55,247 },
89  { 136, 72,184,120,132, 68,180,116,139, 75,187,123,135, 71,183,119 },
90  {  40,232, 24,216, 36,228, 20,212, 43,235, 27,219, 39,231, 23,215 },
91  { 168,104,152, 88,164,100,148, 84,171,107,155, 91,167,103,151, 87 },
92  {   2,194, 50,242, 14,206, 62,254,  1,193, 49,241, 13,205, 61,253 },
93  { 130, 66,178,114,142, 78,190,126,129, 65,177,113,141, 77,189,125 },
94  {  34,226, 18,210, 46,238, 30,222, 33,225, 17,209, 45,237, 29,221 },
95  { 162, 98,146, 82,174,110,158, 94,161, 97,145, 81,173,109,157, 93 },
96  {  10,202, 58,250,  6,198, 54,246,  9,201, 57,249,  5,197, 53,245 },
97  { 138, 74,186,122,134, 70,182,118,137, 73,185,121,133, 69,181,117 },
98  {  42,234, 26,218, 38,230, 22,214, 41,233, 25,217, 37,229, 21,213 },
99  { 170,106,154, 90,166,102,150, 86,169,105,153, 89,165,101,149, 85 }
100};
101
102
103/* Declarations for Floyd-Steinberg dithering.
104 *
105 * Errors are accumulated into the array fserrors[], at a resolution of
106 * 1/16th of a pixel count.  The error at a given pixel is propagated
107 * to its not-yet-processed neighbors using the standard F-S fractions,
108 *              ...     (here)  7/16
109 *              3/16    5/16    1/16
110 * We work left-to-right on even rows, right-to-left on odd rows.
111 *
112 * We can get away with a single array (holding one row's worth of errors)
113 * by using it to store the current row's errors at pixel columns not yet
114 * processed, but the next row's errors at columns already processed.  We
115 * need only a few extra variables to hold the errors immediately around the
116 * current column.  (If we are lucky, those variables are in registers, but
117 * even if not, they're probably cheaper to access than array elements are.)
118 *
119 * The fserrors[] array is indexed [component#][position].
120 * We provide (#columns + 2) entries per component; the extra entry at each
121 * end saves us from special-casing the first and last pixels.
122 *
123 * Note: on a wide image, we might not have enough room in a PC's near data
124 * segment to hold the error array; so it is allocated with alloc_large.
125 */
126
127#if BITS_IN_JSAMPLE == 8
128typedef INT16 FSERROR;          /* 16 bits should be enough */
129typedef int LOCFSERROR;         /* use 'int' for calculation temps */
130#else
131typedef INT32 FSERROR;          /* may need more than 16 bits */
132typedef INT32 LOCFSERROR;       /* be sure calculation temps are big enough */
133#endif
134
135typedef FSERROR FAR *FSERRPTR;  /* pointer to error array (in FAR storage!) */
136
137
138/* Private subobject */
139
140#define MAX_Q_COMPS 4           /* max components I can handle */
141
142typedef struct {
143  struct jpeg_color_quantizer pub; /* public fields */
144
145  /* Initially allocated colormap is saved here */
146  JSAMPARRAY sv_colormap;       /* The color map as a 2-D pixel array */
147  int sv_actual;                /* number of entries in use */
148
149  JSAMPARRAY colorindex;        /* Precomputed mapping for speed */
150  /* colorindex[i][j] = index of color closest to pixel value j in component i,
151   * premultiplied as described above.  Since colormap indexes must fit into
152   * JSAMPLEs, the entries of this array will too.
153   */
154  boolean is_padded;            /* is the colorindex padded for odither? */
155
156  int Ncolors[MAX_Q_COMPS];     /* # of values alloced to each component */
157
158  /* Variables for ordered dithering */
159  int row_index;                /* cur row's vertical index in dither matrix */
160  ODITHER_MATRIX_PTR odither[MAX_Q_COMPS]; /* one dither array per component */
161
162  /* Variables for Floyd-Steinberg dithering */
163  FSERRPTR fserrors[MAX_Q_COMPS]; /* accumulated errors */
164  boolean on_odd_row;           /* flag to remember which row we are on */
165} my_cquantizer;
166
167typedef my_cquantizer * my_cquantize_ptr;
168
169
170/*
171 * Policy-making subroutines for create_colormap and create_colorindex.
172 * These routines determine the colormap to be used.  The rest of the module
173 * only assumes that the colormap is orthogonal.
174 *
175 *  * select_ncolors decides how to divvy up the available colors
176 *    among the components.
177 *  * output_value defines the set of representative values for a component.
178 *  * largest_input_value defines the mapping from input values to
179 *    representative values for a component.
180 * Note that the latter two routines may impose different policies for
181 * different components, though this is not currently done.
182 */
183
184
185LOCAL(int)
186select_ncolors (j_decompress_ptr cinfo, int Ncolors[])
187/* Determine allocation of desired colors to components, */
188/* and fill in Ncolors[] array to indicate choice. */
189/* Return value is total number of colors (product of Ncolors[] values). */
190{
191  int nc = cinfo->out_color_components; /* number of color components */
192  int max_colors = cinfo->desired_number_of_colors;
193  int total_colors, iroot, i, j;
194  boolean changed;
195  long temp;
196  static const int RGB_order[3] = { RGB_GREEN, RGB_RED, RGB_BLUE };
197
198  /* We can allocate at least the nc'th root of max_colors per component. */
199  /* Compute floor(nc'th root of max_colors). */
200  iroot = 1;
201  do {
202    iroot++;
203    temp = iroot;               /* set temp = iroot ** nc */
204    for (i = 1; i < nc; i++)
205      temp *= iroot;
206  } while (temp <= (long) max_colors); /* repeat till iroot exceeds root */
207  iroot--;                      /* now iroot = floor(root) */
208
209  /* Must have at least 2 color values per component */
210  if (iroot < 2)
211    ERREXIT1(cinfo, JERR_QUANT_FEW_COLORS, (int) temp);
212
213  /* Initialize to iroot color values for each component */
214  total_colors = 1;
215  for (i = 0; i < nc; i++) {
216    Ncolors[i] = iroot;
217    total_colors *= iroot;
218  }
219  /* We may be able to increment the count for one or more components without
220   * exceeding max_colors, though we know not all can be incremented.
221   * Sometimes, the first component can be incremented more than once!
222   * (Example: for 16 colors, we start at 2*2*2, go to 3*2*2, then 4*2*2.)
223   * In RGB colorspace, try to increment G first, then R, then B.
224   */
225  do {
226    changed = FALSE;
227    for (i = 0; i < nc; i++) {
228      j = (cinfo->out_color_space == JCS_RGB ? RGB_order[i] : i);
229      /* calculate new total_colors if Ncolors[j] is incremented */
230      temp = total_colors / Ncolors[j];
231      temp *= Ncolors[j]+1;     /* done in long arith to avoid oflo */
232      if (temp > (long) max_colors)
233        break;                  /* won't fit, done with this pass */
234      Ncolors[j]++;             /* OK, apply the increment */
235      total_colors = (int) temp;
236      changed = TRUE;
237    }
238  } while (changed);
239
240  return total_colors;
241}
242
243
244LOCAL(int)
245output_value (j_decompress_ptr cinfo, int ci, int j, int maxj)
246/* Return j'th output value, where j will range from 0 to maxj */
247/* The output values must fall in 0..MAXJSAMPLE in increasing order */
248{
249  /* We always provide values 0 and MAXJSAMPLE for each component;
250   * any additional values are equally spaced between these limits.
251   * (Forcing the upper and lower values to the limits ensures that
252   * dithering can't produce a color outside the selected gamut.)
253   */
254  return (int) (((INT32) j * MAXJSAMPLE + maxj/2) / maxj);
255}
256
257
258LOCAL(int)
259largest_input_value (j_decompress_ptr cinfo, int ci, int j, int maxj)
260/* Return largest input value that should map to j'th output value */
261/* Must have largest(j=0) >= 0, and largest(j=maxj) >= MAXJSAMPLE */
262{
263  /* Breakpoints are halfway between values returned by output_value */
264  return (int) (((INT32) (2*j + 1) * MAXJSAMPLE + maxj) / (2*maxj));
265}
266
267
268/*
269 * Create the colormap.
270 */
271
272LOCAL(void)
273create_colormap (j_decompress_ptr cinfo)
274{
275  my_cquantize_ptr cquantize = (my_cquantize_ptr) cinfo->cquantize;
276  JSAMPARRAY colormap;          /* Created colormap */
277  int total_colors;             /* Number of distinct output colors */
278  int i,j,k, nci, blksize, blkdist, ptr, val;
279
280  /* Select number of colors for each component */
281  total_colors = select_ncolors(cinfo, cquantize->Ncolors);
282
283  /* Report selected color counts */
284  if (cinfo->out_color_components == 3)
285    TRACEMS4(cinfo, 1, JTRC_QUANT_3_NCOLORS,
286             total_colors, cquantize->Ncolors[0],
287             cquantize->Ncolors[1], cquantize->Ncolors[2]);
288  else
289    TRACEMS1(cinfo, 1, JTRC_QUANT_NCOLORS, total_colors);
290
291  /* Allocate and fill in the colormap. */
292  /* The colors are ordered in the map in standard row-major order, */
293  /* i.e. rightmost (highest-indexed) color changes most rapidly. */
294
295  colormap = (*cinfo->mem->alloc_sarray)
296    ((j_common_ptr) cinfo, JPOOL_IMAGE,
297     (JDIMENSION) total_colors, (JDIMENSION) cinfo->out_color_components);
298
299  /* blksize is number of adjacent repeated entries for a component */
300  /* blkdist is distance between groups of identical entries for a component */
301  blkdist = total_colors;
302
303  for (i = 0; i < cinfo->out_color_components; i++) {
304    /* fill in colormap entries for i'th color component */
305    nci = cquantize->Ncolors[i]; /* # of distinct values for this color */
306    blksize = blkdist / nci;
307    for (j = 0; j < nci; j++) {
308      /* Compute j'th output value (out of nci) for component */
309      val = output_value(cinfo, i, j, nci-1);
310      /* Fill in all colormap entries that have this value of this component */
311      for (ptr = j * blksize; ptr < total_colors; ptr += blkdist) {
312        /* fill in blksize entries beginning at ptr */
313        for (k = 0; k < blksize; k++)
314          colormap[i][ptr+k] = (JSAMPLE) val;
315      }
316    }
317    blkdist = blksize;          /* blksize of this color is blkdist of next */
318  }
319
320  /* Save the colormap in private storage,
321   * where it will survive color quantization mode changes.
322   */
323  cquantize->sv_colormap = colormap;
324  cquantize->sv_actual = total_colors;
325}
326
327
328/*
329 * Create the color index table.
330 */
331
332LOCAL(void)
333create_colorindex (j_decompress_ptr cinfo)
334{
335  my_cquantize_ptr cquantize = (my_cquantize_ptr) cinfo->cquantize;
336  JSAMPROW indexptr;
337  int i,j,k, nci, blksize, val, pad;
338
339  /* For ordered dither, we pad the color index tables by MAXJSAMPLE in
340   * each direction (input index values can be -MAXJSAMPLE .. 2*MAXJSAMPLE).
341   * This is not necessary in the other dithering modes.  However, we
342   * flag whether it was done in case user changes dithering mode.
343   */
344  if (cinfo->dither_mode == JDITHER_ORDERED) {
345    pad = MAXJSAMPLE*2;
346    cquantize->is_padded = TRUE;
347  } else {
348    pad = 0;
349    cquantize->is_padded = FALSE;
350  }
351
352  cquantize->colorindex = (*cinfo->mem->alloc_sarray)
353    ((j_common_ptr) cinfo, JPOOL_IMAGE,
354     (JDIMENSION) (MAXJSAMPLE+1 + pad),
355     (JDIMENSION) cinfo->out_color_components);
356
357  /* blksize is number of adjacent repeated entries for a component */
358  blksize = cquantize->sv_actual;
359
360  for (i = 0; i < cinfo->out_color_components; i++) {
361    /* fill in colorindex entries for i'th color component */
362    nci = cquantize->Ncolors[i]; /* # of distinct values for this color */
363    blksize = blksize / nci;
364
365    /* adjust colorindex pointers to provide padding at negative indexes. */
366    if (pad)
367      cquantize->colorindex[i] += MAXJSAMPLE;
368
369    /* in loop, val = index of current output value, */
370    /* and k = largest j that maps to current val */
371    indexptr = cquantize->colorindex[i];
372    val = 0;
373    k = largest_input_value(cinfo, i, 0, nci-1);
374    for (j = 0; j <= MAXJSAMPLE; j++) {
375      while (j > k)             /* advance val if past boundary */
376        k = largest_input_value(cinfo, i, ++val, nci-1);
377      /* premultiply so that no multiplication needed in main processing */
378      indexptr[j] = (JSAMPLE) (val * blksize);
379    }
380    /* Pad at both ends if necessary */
381    if (pad)
382      for (j = 1; j <= MAXJSAMPLE; j++) {
383        indexptr[-j] = indexptr[0];
384        indexptr[MAXJSAMPLE+j] = indexptr[MAXJSAMPLE];
385      }
386  }
387}
388
389
390/*
391 * Create an ordered-dither array for a component having ncolors
392 * distinct output values.
393 */
394
395LOCAL(ODITHER_MATRIX_PTR)
396make_odither_array (j_decompress_ptr cinfo, int ncolors)
397{
398  ODITHER_MATRIX_PTR odither;
399  int j,k;
400  INT32 num,den;
401
402  odither = (ODITHER_MATRIX_PTR)
403    (*cinfo->mem->alloc_small) ((j_common_ptr) cinfo, JPOOL_IMAGE,
404                                SIZEOF(ODITHER_MATRIX));
405  /* The inter-value distance for this color is MAXJSAMPLE/(ncolors-1).
406   * Hence the dither value for the matrix cell with fill order f
407   * (f=0..N-1) should be (N-1-2*f)/(2*N) * MAXJSAMPLE/(ncolors-1).
408   * On 16-bit-int machine, be careful to avoid overflow.
409   */
410  den = 2 * ODITHER_CELLS * ((INT32) (ncolors - 1));
411  for (j = 0; j < ODITHER_SIZE; j++) {
412    for (k = 0; k < ODITHER_SIZE; k++) {
413      num = ((INT32) (ODITHER_CELLS-1 - 2*((int)base_dither_matrix[j][k])))
414            * MAXJSAMPLE;
415      /* Ensure round towards zero despite C's lack of consistency
416       * about rounding negative values in integer division...
417       */
418      odither[j][k] = (int) (num<0 ? -((-num)/den) : num/den);
419    }
420  }
421  return odither;
422}
423
424
425/*
426 * Create the ordered-dither tables.
427 * Components having the same number of representative colors may
428 * share a dither table.
429 */
430
431LOCAL(void)
432create_odither_tables (j_decompress_ptr cinfo)
433{
434  my_cquantize_ptr cquantize = (my_cquantize_ptr) cinfo->cquantize;
435  ODITHER_MATRIX_PTR odither;
436  int i, j, nci;
437
438  for (i = 0; i < cinfo->out_color_components; i++) {
439    nci = cquantize->Ncolors[i]; /* # of distinct values for this color */
440    odither = NULL;             /* search for matching prior component */
441    for (j = 0; j < i; j++) {
442      if (nci == cquantize->Ncolors[j]) {
443        odither = cquantize->odither[j];
444        break;
445      }
446    }
447    if (odither == NULL)        /* need a new table? */
448      odither = make_odither_array(cinfo, nci);
449    cquantize->odither[i] = odither;
450  }
451}
452
453
454/*
455 * Map some rows of pixels to the output colormapped representation.
456 */
457
458METHODDEF(void)
459color_quantize (j_decompress_ptr cinfo, JSAMPARRAY input_buf,
460                JSAMPARRAY output_buf, int num_rows)
461/* General case, no dithering */
462{
463  my_cquantize_ptr cquantize = (my_cquantize_ptr) cinfo->cquantize;
464  JSAMPARRAY colorindex = cquantize->colorindex;
465  register int pixcode, ci;
466  register JSAMPROW ptrin, ptrout;
467  int row;
468  JDIMENSION col;
469  JDIMENSION width = cinfo->output_width;
470  register int nc = cinfo->out_color_components;
471
472  for (row = 0; row < num_rows; row++) {
473    ptrin = input_buf[row];
474    ptrout = output_buf[row];
475    for (col = width; col > 0; col--) {
476      pixcode = 0;
477      for (ci = 0; ci < nc; ci++) {
478        pixcode += GETJSAMPLE(colorindex[ci][GETJSAMPLE(*ptrin++)]);
479      }
480      *ptrout++ = (JSAMPLE) pixcode;
481    }
482  }
483}
484
485
486METHODDEF(void)
487color_quantize3 (j_decompress_ptr cinfo, JSAMPARRAY input_buf,
488                 JSAMPARRAY output_buf, int num_rows)
489/* Fast path for out_color_components==3, no dithering */
490{
491  my_cquantize_ptr cquantize = (my_cquantize_ptr) cinfo->cquantize;
492  register int pixcode;
493  register JSAMPROW ptrin, ptrout;
494  JSAMPROW colorindex0 = cquantize->colorindex[0];
495  JSAMPROW colorindex1 = cquantize->colorindex[1];
496  JSAMPROW colorindex2 = cquantize->colorindex[2];
497  int row;
498  JDIMENSION col;
499  JDIMENSION width = cinfo->output_width;
500
501  for (row = 0; row < num_rows; row++) {
502    ptrin = input_buf[row];
503    ptrout = output_buf[row];
504    for (col = width; col > 0; col--) {
505      pixcode  = GETJSAMPLE(colorindex0[GETJSAMPLE(*ptrin++)]);
506      pixcode += GETJSAMPLE(colorindex1[GETJSAMPLE(*ptrin++)]);
507      pixcode += GETJSAMPLE(colorindex2[GETJSAMPLE(*ptrin++)]);
508      *ptrout++ = (JSAMPLE) pixcode;
509    }
510  }
511}
512
513
514METHODDEF(void)
515quantize_ord_dither (j_decompress_ptr cinfo, JSAMPARRAY input_buf,
516                     JSAMPARRAY output_buf, int num_rows)
517/* General case, with ordered dithering */
518{
519  my_cquantize_ptr cquantize = (my_cquantize_ptr) cinfo->cquantize;
520  register JSAMPROW input_ptr;
521  register JSAMPROW output_ptr;
522  JSAMPROW colorindex_ci;
523  int * dither;                 /* points to active row of dither matrix */
524  int row_index, col_index;     /* current indexes into dither matrix */
525  int nc = cinfo->out_color_components;
526  int ci;
527  int row;
528  JDIMENSION col;
529  JDIMENSION width = cinfo->output_width;
530
531  for (row = 0; row < num_rows; row++) {
532    /* Initialize output values to 0 so can process components separately */
533    jzero_far((void FAR *) output_buf[row],
534              (size_t) (width * SIZEOF(JSAMPLE)));
535    row_index = cquantize->row_index;
536    for (ci = 0; ci < nc; ci++) {
537      input_ptr = input_buf[row] + ci;
538      output_ptr = output_buf[row];
539      colorindex_ci = cquantize->colorindex[ci];
540      dither = cquantize->odither[ci][row_index];
541      col_index = 0;
542
543      for (col = width; col > 0; col--) {
544        /* Form pixel value + dither, range-limit to 0..MAXJSAMPLE,
545         * select output value, accumulate into output code for this pixel.
546         * Range-limiting need not be done explicitly, as we have extended
547         * the colorindex table to produce the right answers for out-of-range
548         * inputs.  The maximum dither is +- MAXJSAMPLE; this sets the
549         * required amount of padding.
550         */
551        *output_ptr += colorindex_ci[GETJSAMPLE(*input_ptr)+dither[col_index]];
552        input_ptr += nc;
553        output_ptr++;
554        col_index = (col_index + 1) & ODITHER_MASK;
555      }
556    }
557    /* Advance row index for next row */
558    row_index = (row_index + 1) & ODITHER_MASK;
559    cquantize->row_index = row_index;
560  }
561}
562
563
564METHODDEF(void)
565quantize3_ord_dither (j_decompress_ptr cinfo, JSAMPARRAY input_buf,
566                      JSAMPARRAY output_buf, int num_rows)
567/* Fast path for out_color_components==3, with ordered dithering */
568{
569  my_cquantize_ptr cquantize = (my_cquantize_ptr) cinfo->cquantize;
570  register int pixcode;
571  register JSAMPROW input_ptr;
572  register JSAMPROW output_ptr;
573  JSAMPROW colorindex0 = cquantize->colorindex[0];
574  JSAMPROW colorindex1 = cquantize->colorindex[1];
575  JSAMPROW colorindex2 = cquantize->colorindex[2];
576  int * dither0;                /* points to active row of dither matrix */
577  int * dither1;
578  int * dither2;
579  int row_index, col_index;     /* current indexes into dither matrix */
580  int row;
581  JDIMENSION col;
582  JDIMENSION width = cinfo->output_width;
583
584  for (row = 0; row < num_rows; row++) {
585    row_index = cquantize->row_index;
586    input_ptr = input_buf[row];
587    output_ptr = output_buf[row];
588    dither0 = cquantize->odither[0][row_index];
589    dither1 = cquantize->odither[1][row_index];
590    dither2 = cquantize->odither[2][row_index];
591    col_index = 0;
592
593    for (col = width; col > 0; col--) {
594      pixcode  = GETJSAMPLE(colorindex0[GETJSAMPLE(*input_ptr++) +
595                                        dither0[col_index]]);
596      pixcode += GETJSAMPLE(colorindex1[GETJSAMPLE(*input_ptr++) +
597                                        dither1[col_index]]);
598      pixcode += GETJSAMPLE(colorindex2[GETJSAMPLE(*input_ptr++) +
599                                        dither2[col_index]]);
600      *output_ptr++ = (JSAMPLE) pixcode;
601      col_index = (col_index + 1) & ODITHER_MASK;
602    }
603    row_index = (row_index + 1) & ODITHER_MASK;
604    cquantize->row_index = row_index;
605  }
606}
607
608
609METHODDEF(void)
610quantize_fs_dither (j_decompress_ptr cinfo, JSAMPARRAY input_buf,
611                    JSAMPARRAY output_buf, int num_rows)
612/* General case, with Floyd-Steinberg dithering */
613{
614  my_cquantize_ptr cquantize = (my_cquantize_ptr) cinfo->cquantize;
615  register LOCFSERROR cur;      /* current error or pixel value */
616  LOCFSERROR belowerr;          /* error for pixel below cur */
617  LOCFSERROR bpreverr;          /* error for below/prev col */
618  LOCFSERROR bnexterr;          /* error for below/next col */
619  LOCFSERROR delta;
620  register FSERRPTR errorptr;   /* => fserrors[] at column before current */
621  register JSAMPROW input_ptr;
622  register JSAMPROW output_ptr;
623  JSAMPROW colorindex_ci;
624  JSAMPROW colormap_ci;
625  int pixcode;
626  int nc = cinfo->out_color_components;
627  int dir;                      /* 1 for left-to-right, -1 for right-to-left */
628  int dirnc;                    /* dir * nc */
629  int ci;
630  int row;
631  JDIMENSION col;
632  JDIMENSION width = cinfo->output_width;
633  JSAMPLE *range_limit = cinfo->sample_range_limit;
634  SHIFT_TEMPS
635
636  for (row = 0; row < num_rows; row++) {
637    /* Initialize output values to 0 so can process components separately */
638    jzero_far((void FAR *) output_buf[row],
639              (size_t) (width * SIZEOF(JSAMPLE)));
640    for (ci = 0; ci < nc; ci++) {
641      input_ptr = input_buf[row] + ci;
642      output_ptr = output_buf[row];
643      if (cquantize->on_odd_row) {
644        /* work right to left in this row */
645        input_ptr += (width-1) * nc; /* so point to rightmost pixel */
646        output_ptr += width-1;
647        dir = -1;
648        dirnc = -nc;
649        errorptr = cquantize->fserrors[ci] + (width+1); /* => entry after last column */
650      } else {
651        /* work left to right in this row */
652        dir = 1;
653        dirnc = nc;
654        errorptr = cquantize->fserrors[ci]; /* => entry before first column */
655      }
656      colorindex_ci = cquantize->colorindex[ci];
657      colormap_ci = cquantize->sv_colormap[ci];
658      /* Preset error values: no error propagated to first pixel from left */
659      cur = 0;
660      /* and no error propagated to row below yet */
661      belowerr = bpreverr = 0;
662
663      for (col = width; col > 0; col--) {
664        /* cur holds the error propagated from the previous pixel on the
665         * current line.  Add the error propagated from the previous line
666         * to form the complete error correction term for this pixel, and
667         * round the error term (which is expressed * 16) to an integer.
668         * RIGHT_SHIFT rounds towards minus infinity, so adding 8 is correct
669         * for either sign of the error value.
670         * Note: errorptr points to *previous* column's array entry.
671         */
672        cur = RIGHT_SHIFT(cur + errorptr[dir] + 8, 4);
673        /* Form pixel value + error, and range-limit to 0..MAXJSAMPLE.
674         * The maximum error is +- MAXJSAMPLE; this sets the required size
675         * of the range_limit array.
676         */
677        cur += GETJSAMPLE(*input_ptr);
678        cur = GETJSAMPLE(range_limit[cur]);
679        /* Select output value, accumulate into output code for this pixel */
680        pixcode = GETJSAMPLE(colorindex_ci[cur]);
681        *output_ptr += (JSAMPLE) pixcode;
682        /* Compute actual representation error at this pixel */
683        /* Note: we can do this even though we don't have the final */
684        /* pixel code, because the colormap is orthogonal. */
685        cur -= GETJSAMPLE(colormap_ci[pixcode]);
686        /* Compute error fractions to be propagated to adjacent pixels.
687         * Add these into the running sums, and simultaneously shift the
688         * next-line error sums left by 1 column.
689         */
690        bnexterr = cur;
691        delta = cur * 2;
692        cur += delta;           /* form error * 3 */
693        errorptr[0] = (FSERROR) (bpreverr + cur);
694        cur += delta;           /* form error * 5 */
695        bpreverr = belowerr + cur;
696        belowerr = bnexterr;
697        cur += delta;           /* form error * 7 */
698        /* At this point cur contains the 7/16 error value to be propagated
699         * to the next pixel on the current line, and all the errors for the
700         * next line have been shifted over. We are therefore ready to move on.
701         */
702        input_ptr += dirnc;     /* advance input ptr to next column */
703        output_ptr += dir;      /* advance output ptr to next column */
704        errorptr += dir;        /* advance errorptr to current column */
705      }
706      /* Post-loop cleanup: we must unload the final error value into the
707       * final fserrors[] entry.  Note we need not unload belowerr because
708       * it is for the dummy column before or after the actual array.
709       */
710      errorptr[0] = (FSERROR) bpreverr; /* unload prev err into array */
711    }
712    cquantize->on_odd_row = (cquantize->on_odd_row ? FALSE : TRUE);
713  }
714}
715
716
717/*
718 * Allocate workspace for Floyd-Steinberg errors.
719 */
720
721LOCAL(void)
722alloc_fs_workspace (j_decompress_ptr cinfo)
723{
724  my_cquantize_ptr cquantize = (my_cquantize_ptr) cinfo->cquantize;
725  size_t arraysize;
726  int i;
727
728  arraysize = (size_t) ((cinfo->output_width + 2) * SIZEOF(FSERROR));
729  for (i = 0; i < cinfo->out_color_components; i++) {
730    cquantize->fserrors[i] = (FSERRPTR)
731      (*cinfo->mem->alloc_large)((j_common_ptr) cinfo, JPOOL_IMAGE, arraysize);
732  }
733}
734
735
736/*
737 * Initialize for one-pass color quantization.
738 */
739
740METHODDEF(void)
741start_pass_1_quant (j_decompress_ptr cinfo, boolean is_pre_scan)
742{
743  my_cquantize_ptr cquantize = (my_cquantize_ptr) cinfo->cquantize;
744  size_t arraysize;
745  int i;
746
747  /* Install my colormap. */
748  cinfo->colormap = cquantize->sv_colormap;
749  cinfo->actual_number_of_colors = cquantize->sv_actual;
750
751  /* Initialize for desired dithering mode. */
752  switch (cinfo->dither_mode) {
753  case JDITHER_NONE:
754    if (cinfo->out_color_components == 3)
755      cquantize->pub.color_quantize = color_quantize3;
756    else
757      cquantize->pub.color_quantize = color_quantize;
758    break;
759  case JDITHER_ORDERED:
760    if (cinfo->out_color_components == 3)
761      cquantize->pub.color_quantize = quantize3_ord_dither;
762    else
763      cquantize->pub.color_quantize = quantize_ord_dither;
764    cquantize->row_index = 0;   /* initialize state for ordered dither */
765    /* If user changed to ordered dither from another mode,
766     * we must recreate the color index table with padding.
767     * This will cost extra space, but probably isn't very likely.
768     */
769    if (! cquantize->is_padded)
770      create_colorindex(cinfo);
771    /* Create ordered-dither tables if we didn't already. */
772    if (cquantize->odither[0] == NULL)
773      create_odither_tables(cinfo);
774    break;
775  case JDITHER_FS:
776    cquantize->pub.color_quantize = quantize_fs_dither;
777    cquantize->on_odd_row = FALSE; /* initialize state for F-S dither */
778    /* Allocate Floyd-Steinberg workspace if didn't already. */
779    if (cquantize->fserrors[0] == NULL)
780      alloc_fs_workspace(cinfo);
781    /* Initialize the propagated errors to zero. */
782    arraysize = (size_t) ((cinfo->output_width + 2) * SIZEOF(FSERROR));
783    for (i = 0; i < cinfo->out_color_components; i++)
784      jzero_far((void FAR *) cquantize->fserrors[i], arraysize);
785    break;
786  default:
787    ERREXIT(cinfo, JERR_NOT_COMPILED);
788    break;
789  }
790}
791
792
793/*
794 * Finish up at the end of the pass.
795 */
796
797METHODDEF(void)
798finish_pass_1_quant (j_decompress_ptr cinfo)
799{
800  /* no work in 1-pass case */
801}
802
803
804/*
805 * Switch to a new external colormap between output passes.
806 * Shouldn't get to this module!
807 */
808
809METHODDEF(void)
810new_color_map_1_quant (j_decompress_ptr cinfo)
811{
812  ERREXIT(cinfo, JERR_MODE_CHANGE);
813}
814
815
816/*
817 * Module initialization routine for 1-pass color quantization.
818 */
819
820GLOBAL(void)
821jinit_1pass_quantizer (j_decompress_ptr cinfo)
822{
823  my_cquantize_ptr cquantize;
824
825  cquantize = (my_cquantize_ptr)
826    (*cinfo->mem->alloc_small) ((j_common_ptr) cinfo, JPOOL_IMAGE,
827                                SIZEOF(my_cquantizer));
828  cinfo->cquantize = (struct jpeg_color_quantizer *) cquantize;
829  cquantize->pub.start_pass = start_pass_1_quant;
830  cquantize->pub.finish_pass = finish_pass_1_quant;
831  cquantize->pub.new_color_map = new_color_map_1_quant;
832  cquantize->fserrors[0] = NULL; /* Flag FS workspace not allocated */
833  cquantize->odither[0] = NULL; /* Also flag odither arrays not allocated */
834
835  /* Make sure my internal arrays won't overflow */
836  if (cinfo->out_color_components > MAX_Q_COMPS)
837    ERREXIT1(cinfo, JERR_QUANT_COMPONENTS, MAX_Q_COMPS);
838  /* Make sure colormap indexes can be represented by JSAMPLEs */
839  if (cinfo->desired_number_of_colors > (MAXJSAMPLE+1))
840    ERREXIT1(cinfo, JERR_QUANT_MANY_COLORS, MAXJSAMPLE+1);
841
842  /* Create the colormap and color index table. */
843  create_colormap(cinfo);
844  create_colorindex(cinfo);
845
846  /* Allocate Floyd-Steinberg workspace now if requested.
847   * We do this now since it is FAR storage and may affect the memory
848   * manager's space calculations.  If the user changes to FS dither
849   * mode in a later pass, we will allocate the space then, and will
850   * possibly overrun the max_memory_to_use setting.
851   */
852  if (cinfo->dither_mode == JDITHER_FS)
853    alloc_fs_workspace(cinfo);
854}
855
856#endif /* QUANT_1PASS_SUPPORTED */
Note: See TracBrowser for help on using the repository browser.