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