1 /*
2 * jcphuff.c
3 *
4 * Copyright (C) 1995-1997, 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 Huffman entropy encoding routines for progressive JPEG.
9 *
10 * We do not support output suspension in this module, since the library
11 * currently does not allow multiple-scan files to be written with output
12 * suspension.
13 */
14
15 #define JPEG_INTERNALS
16 #include "jinclude.h"
17 #include "jpeglib.h"
18 #include "jchuff.h" /* Declarations shared with jchuff.c */
19
20 #ifdef C_PROGRESSIVE_SUPPORTED
21
22 /* Expanded entropy encoder object for progressive Huffman encoding. */
23
24 typedef struct {
25 struct jpeg_entropy_encoder pub; /* public fields */
26
27 /* Mode flag: TRUE for optimization, FALSE for actual data output */
28 boolean gather_statistics;
29
30 /* Bit-level coding status.
31 * next_output_byte/free_in_buffer are local copies of cinfo->dest fields.
32 */
33 JOCTET * next_output_byte; /* => next byte to write in buffer */
34 size_t free_in_buffer; /* # of byte spaces remaining in buffer */
35 INT32 put_buffer; /* current bit-accumulation buffer */
36 int put_bits; /* # of bits now in it */
37 j_compress_ptr cinfo; /* link to cinfo (needed for dump_buffer) */
38
39 /* Coding status for DC components */
40 int last_dc_val[MAX_COMPS_IN_SCAN]; /* last DC coef for each component */
41
42 /* Coding status for AC components */
43 int ac_tbl_no; /* the table number of the single component */
44 unsigned int EOBRUN; /* run length of EOBs */
45 unsigned int BE; /* # of buffered correction bits before MCU */
46 char * bit_buffer; /* buffer for correction bits (1 per char) */
47 /* packing correction bits tightly would save some space but cost time... */
48
49 unsigned int restarts_to_go; /* MCUs left in this restart interval */
50 int next_restart_num; /* next restart number to write (0-7) */
51
52 /* Pointers to derived tables (these workspaces have image lifespan).
53 * Since any one scan codes only DC or only AC, we only need one set
54 * of tables, not one for DC and one for AC.
55 */
56 c_derived_tbl * derived_tbls[NUM_HUFF_TBLS];
57
58 /* Statistics tables for optimization; again, one set is enough */
59 long * count_ptrs[NUM_HUFF_TBLS];
60 } phuff_entropy_encoder;
61
62 typedef phuff_entropy_encoder * phuff_entropy_ptr;
63
64 /* MAX_CORR_BITS is the number of bits the AC refinement correction-bit
65 * buffer can hold. Larger sizes may slightly improve compression, but
66 * 1000 is already well into the realm of overkill.
67 * The minimum safe size is 64 bits.
68 */
69
70 #define MAX_CORR_BITS 1000 /* Max # of correction bits I can buffer */
71
72 /* IRIGHT_SHIFT is like RIGHT_SHIFT, but works on int rather than INT32.
73 * We assume that int right shift is unsigned if INT32 right shift is,
74 * which should be safe.
75 */
76
77 #ifdef RIGHT_SHIFT_IS_UNSIGNED
78 #define ISHIFT_TEMPS int ishift_temp;
79 #define IRIGHT_SHIFT(x,shft) \
80 ((ishift_temp = (x)) < 0 ? \
81 (ishift_temp >> (shft)) | ((~0) << (16-(shft))) : \
82 (ishift_temp >> (shft)))
83 #else
84 #define ISHIFT_TEMPS
85 #define IRIGHT_SHIFT(x,shft) ((x) >> (shft))
86 #endif
87
88 /* Forward declarations */
89 METHODDEF(boolean) encode_mcu_DC_first JPP((j_compress_ptr cinfo,
90 JBLOCKROW *MCU_data));
91 METHODDEF(boolean) encode_mcu_AC_first JPP((j_compress_ptr cinfo,
92 JBLOCKROW *MCU_data));
93 METHODDEF(boolean) encode_mcu_DC_refine JPP((j_compress_ptr cinfo,
94 JBLOCKROW *MCU_data));
95 METHODDEF(boolean) encode_mcu_AC_refine JPP((j_compress_ptr cinfo,
96 JBLOCKROW *MCU_data));
97 METHODDEF(void) finish_pass_phuff JPP((j_compress_ptr cinfo));
98 METHODDEF(void) finish_pass_gather_phuff JPP((j_compress_ptr cinfo));
99
100
101 /*
102 * Initialize for a Huffman-compressed scan using progressive JPEG.
103 */
104
105 METHODDEF(void)
start_pass_phuff(j_compress_ptr cinfo,boolean gather_statistics)106 start_pass_phuff (j_compress_ptr cinfo, boolean gather_statistics)
107 {
108 phuff_entropy_ptr entropy = (phuff_entropy_ptr) cinfo->entropy;
109 boolean is_DC_band;
110 int ci, tbl;
111 jpeg_component_info * compptr;
112
113 entropy->cinfo = cinfo;
114 entropy->gather_statistics = gather_statistics;
115
116 is_DC_band = (cinfo->Ss == 0);
117
118 /* We assume jcmaster.c already validated the scan parameters. */
119
120 /* Select execution routines */
121 if (cinfo->Ah == 0) {
122 if (is_DC_band)
123 entropy->pub.encode_mcu = encode_mcu_DC_first;
124 else
125 entropy->pub.encode_mcu = encode_mcu_AC_first;
126 } else {
127 if (is_DC_band)
128 entropy->pub.encode_mcu = encode_mcu_DC_refine;
129 else {
130 entropy->pub.encode_mcu = encode_mcu_AC_refine;
131 /* AC refinement needs a correction bit buffer */
132 if (entropy->bit_buffer == NULL)
133 entropy->bit_buffer = (char *)
134 (*cinfo->mem->alloc_small) ((j_common_ptr) cinfo, JPOOL_IMAGE,
135 MAX_CORR_BITS * SIZEOF(char));
136 }
137 }
138 if (gather_statistics)
139 entropy->pub.finish_pass = finish_pass_gather_phuff;
140 else
141 entropy->pub.finish_pass = finish_pass_phuff;
142
143 /* Only DC coefficients may be interleaved, so cinfo->comps_in_scan = 1
144 * for AC coefficients.
145 */
146 for (ci = 0; ci < cinfo->comps_in_scan; ci++) {
147 compptr = cinfo->cur_comp_info[ci];
148 /* Initialize DC predictions to 0 */
149 entropy->last_dc_val[ci] = 0;
150 /* Get table index */
151 if (is_DC_band) {
152 if (cinfo->Ah != 0) /* DC refinement needs no table */
153 continue;
154 tbl = compptr->dc_tbl_no;
155 } else {
156 entropy->ac_tbl_no = tbl = compptr->ac_tbl_no;
157 }
158 if (gather_statistics) {
159 /* Check for invalid table index */
160 /* (make_c_derived_tbl does this in the other path) */
161 if (tbl < 0 || tbl >= NUM_HUFF_TBLS)
162 ERREXIT1(cinfo, JERR_NO_HUFF_TABLE, tbl);
163 /* Allocate and zero the statistics tables */
164 /* Note that jpeg_gen_optimal_table expects 257 entries in each table! */
165 if (entropy->count_ptrs[tbl] == NULL)
166 entropy->count_ptrs[tbl] = (long *)
167 (*cinfo->mem->alloc_small) ((j_common_ptr) cinfo, JPOOL_IMAGE,
168 257 * SIZEOF(long));
169 MEMZERO(entropy->count_ptrs[tbl], 257 * SIZEOF(long));
170 } else {
171 /* Compute derived values for Huffman table */
172 /* We may do this more than once for a table, but it's not expensive */
173 jpeg_make_c_derived_tbl(cinfo, is_DC_band, tbl,
174 & entropy->derived_tbls[tbl]);
175 }
176 }
177
178 /* Initialize AC stuff */
179 entropy->EOBRUN = 0;
180 entropy->BE = 0;
181
182 /* Initialize bit buffer to empty */
183 entropy->put_buffer = 0;
184 entropy->put_bits = 0;
185
186 /* Initialize restart stuff */
187 entropy->restarts_to_go = cinfo->restart_interval;
188 entropy->next_restart_num = 0;
189 }
190
191
192 /* Outputting bytes to the file.
193 * NB: these must be called only when actually outputting,
194 * that is, entropy->gather_statistics == FALSE.
195 */
196
197 /* Emit a byte */
198 #define emit_byte(entropy,val) \
199 { *(entropy)->next_output_byte++ = (JOCTET) (val); \
200 if (--(entropy)->free_in_buffer == 0) \
201 dump_buffer(entropy); }
202
203
204 LOCAL(void)
dump_buffer(phuff_entropy_ptr entropy)205 dump_buffer (phuff_entropy_ptr entropy)
206 /* Empty the output buffer; we do not support suspension in this module. */
207 {
208 struct jpeg_destination_mgr * dest = entropy->cinfo->dest;
209
210 if (! (*dest->empty_output_buffer) (entropy->cinfo))
211 ERREXIT(entropy->cinfo, JERR_CANT_SUSPEND);
212 /* After a successful buffer dump, must reset buffer pointers */
213 entropy->next_output_byte = dest->next_output_byte;
214 entropy->free_in_buffer = dest->free_in_buffer;
215 }
216
217
218 /* Outputting bits to the file */
219
220 /* Only the right 24 bits of put_buffer are used; the valid bits are
221 * left-justified in this part. At most 16 bits can be passed to emit_bits
222 * in one call, and we never retain more than 7 bits in put_buffer
223 * between calls, so 24 bits are sufficient.
224 */
225
226 INLINE
LOCAL(void)227 LOCAL(void)
228 emit_bits (phuff_entropy_ptr entropy, unsigned int code, int size)
229 /* Emit some bits, unless we are in gather mode */
230 {
231 /* This routine is heavily used, so it's worth coding tightly. */
232 register INT32 put_buffer = (INT32) code;
233 register int put_bits = entropy->put_bits;
234
235 /* if size is 0, caller used an invalid Huffman table entry */
236 if (size == 0)
237 ERREXIT(entropy->cinfo, JERR_HUFF_MISSING_CODE);
238
239 if (entropy->gather_statistics)
240 return; /* do nothing if we're only getting stats */
241
242 put_buffer &= (((INT32) 1)<<size) - 1; /* mask off any extra bits in code */
243
244 put_bits += size; /* new number of bits in buffer */
245
246 put_buffer <<= 24 - put_bits; /* align incoming bits */
247
248 put_buffer |= entropy->put_buffer; /* and merge with old buffer contents */
249
250 while (put_bits >= 8) {
251 int c = (int) ((put_buffer >> 16) & 0xFF);
252
253 emit_byte(entropy, c);
254 if (c == 0xFF) { /* need to stuff a zero byte? */
255 emit_byte(entropy, 0);
256 }
257 put_buffer <<= 8;
258 put_bits -= 8;
259 }
260
261 entropy->put_buffer = put_buffer; /* update variables */
262 entropy->put_bits = put_bits;
263 }
264
265
266 LOCAL(void)
flush_bits(phuff_entropy_ptr entropy)267 flush_bits (phuff_entropy_ptr entropy)
268 {
269 emit_bits(entropy, 0x7F, 7); /* fill any partial byte with ones */
270 entropy->put_buffer = 0; /* and reset bit-buffer to empty */
271 entropy->put_bits = 0;
272 }
273
274
275 /*
276 * Emit (or just count) a Huffman symbol.
277 */
278
279 INLINE
LOCAL(void)280 LOCAL(void)
281 emit_symbol (phuff_entropy_ptr entropy, int tbl_no, int symbol)
282 {
283 if (entropy->gather_statistics)
284 entropy->count_ptrs[tbl_no][symbol]++;
285 else {
286 c_derived_tbl * tbl = entropy->derived_tbls[tbl_no];
287 emit_bits(entropy, tbl->ehufco[symbol], tbl->ehufsi[symbol]);
288 }
289 }
290
291
292 /*
293 * Emit bits from a correction bit buffer.
294 */
295
296 LOCAL(void)
emit_buffered_bits(phuff_entropy_ptr entropy,char * bufstart,unsigned int nbits)297 emit_buffered_bits (phuff_entropy_ptr entropy, char * bufstart,
298 unsigned int nbits)
299 {
300 if (entropy->gather_statistics)
301 return; /* no real work */
302
303 while (nbits > 0) {
304 emit_bits(entropy, (unsigned int) (*bufstart), 1);
305 bufstart++;
306 nbits--;
307 }
308 }
309
310
311 /*
312 * Emit any pending EOBRUN symbol.
313 */
314
315 LOCAL(void)
emit_eobrun(phuff_entropy_ptr entropy)316 emit_eobrun (phuff_entropy_ptr entropy)
317 {
318 register int temp, nbits;
319
320 if (entropy->EOBRUN > 0) { /* if there is any pending EOBRUN */
321 temp = entropy->EOBRUN;
322 nbits = 0;
323 while ((temp >>= 1))
324 nbits++;
325 /* safety check: shouldn't happen given limited correction-bit buffer */
326 if (nbits > 14)
327 ERREXIT(entropy->cinfo, JERR_HUFF_MISSING_CODE);
328
329 emit_symbol(entropy, entropy->ac_tbl_no, nbits << 4);
330 if (nbits)
331 emit_bits(entropy, entropy->EOBRUN, nbits);
332
333 entropy->EOBRUN = 0;
334
335 /* Emit any buffered correction bits */
336 emit_buffered_bits(entropy, entropy->bit_buffer, entropy->BE);
337 entropy->BE = 0;
338 }
339 }
340
341
342 /*
343 * Emit a restart marker & resynchronize predictions.
344 */
345
346 LOCAL(void)
emit_restart(phuff_entropy_ptr entropy,int restart_num)347 emit_restart (phuff_entropy_ptr entropy, int restart_num)
348 {
349 int ci;
350
351 emit_eobrun(entropy);
352
353 if (! entropy->gather_statistics) {
354 flush_bits(entropy);
355 emit_byte(entropy, 0xFF);
356 emit_byte(entropy, JPEG_RST0 + restart_num);
357 }
358
359 if (entropy->cinfo->Ss == 0) {
360 /* Re-initialize DC predictions to 0 */
361 for (ci = 0; ci < entropy->cinfo->comps_in_scan; ci++)
362 entropy->last_dc_val[ci] = 0;
363 } else {
364 /* Re-initialize all AC-related fields to 0 */
365 entropy->EOBRUN = 0;
366 entropy->BE = 0;
367 }
368 }
369
370
371 /*
372 * MCU encoding for DC initial scan (either spectral selection,
373 * or first pass of successive approximation).
374 */
375
376 METHODDEF(boolean)
encode_mcu_DC_first(j_compress_ptr cinfo,JBLOCKROW * MCU_data)377 encode_mcu_DC_first (j_compress_ptr cinfo, JBLOCKROW *MCU_data)
378 {
379 phuff_entropy_ptr entropy = (phuff_entropy_ptr) cinfo->entropy;
380 register int temp, temp2;
381 register int nbits;
382 int blkn, ci;
383 int Al = cinfo->Al;
384 JBLOCKROW block;
385 jpeg_component_info * compptr;
386 ISHIFT_TEMPS
387
388 entropy->next_output_byte = cinfo->dest->next_output_byte;
389 entropy->free_in_buffer = cinfo->dest->free_in_buffer;
390
391 /* Emit restart marker if needed */
392 if (cinfo->restart_interval)
393 if (entropy->restarts_to_go == 0)
394 emit_restart(entropy, entropy->next_restart_num);
395
396 /* Encode the MCU data blocks */
397 for (blkn = 0; blkn < cinfo->blocks_in_MCU; blkn++) {
398 block = MCU_data[blkn];
399 ci = cinfo->MCU_membership[blkn];
400 compptr = cinfo->cur_comp_info[ci];
401
402 /* Compute the DC value after the required point transform by Al.
403 * This is simply an arithmetic right shift.
404 */
405 temp2 = IRIGHT_SHIFT((int) ((*block)[0]), Al);
406
407 /* DC differences are figured on the point-transformed values. */
408 temp = temp2 - entropy->last_dc_val[ci];
409 entropy->last_dc_val[ci] = temp2;
410
411 /* Encode the DC coefficient difference per section G.1.2.1 */
412 temp2 = temp;
413 if (temp < 0) {
414 temp = -temp; /* temp is abs value of input */
415 /* For a negative input, want temp2 = bitwise complement of abs(input) */
416 /* This code assumes we are on a two's complement machine */
417 temp2--;
418 }
419
420 /* Find the number of bits needed for the magnitude of the coefficient */
421 nbits = 0;
422 while (temp) {
423 nbits++;
424 temp >>= 1;
425 }
426 /* Check for out-of-range coefficient values.
427 * Since we're encoding a difference, the range limit is twice as much.
428 */
429 if (nbits > MAX_COEF_BITS+1)
430 ERREXIT(cinfo, JERR_BAD_DCT_COEF);
431
432 /* Count/emit the Huffman-coded symbol for the number of bits */
433 emit_symbol(entropy, compptr->dc_tbl_no, nbits);
434
435 /* Emit that number of bits of the value, if positive, */
436 /* or the complement of its magnitude, if negative. */
437 if (nbits) /* emit_bits rejects calls with size 0 */
438 emit_bits(entropy, (unsigned int) temp2, nbits);
439 }
440
441 cinfo->dest->next_output_byte = entropy->next_output_byte;
442 cinfo->dest->free_in_buffer = entropy->free_in_buffer;
443
444 /* Update restart-interval state too */
445 if (cinfo->restart_interval) {
446 if (entropy->restarts_to_go == 0) {
447 entropy->restarts_to_go = cinfo->restart_interval;
448 entropy->next_restart_num++;
449 entropy->next_restart_num &= 7;
450 }
451 entropy->restarts_to_go--;
452 }
453
454 return TRUE;
455 }
456
457
458 /*
459 * MCU encoding for AC initial scan (either spectral selection,
460 * or first pass of successive approximation).
461 */
462
463 METHODDEF(boolean)
encode_mcu_AC_first(j_compress_ptr cinfo,JBLOCKROW * MCU_data)464 encode_mcu_AC_first (j_compress_ptr cinfo, JBLOCKROW *MCU_data)
465 {
466 phuff_entropy_ptr entropy = (phuff_entropy_ptr) cinfo->entropy;
467 register int temp, temp2;
468 register int nbits;
469 register int r, k;
470 int Se = cinfo->Se;
471 int Al = cinfo->Al;
472 JBLOCKROW block;
473
474 entropy->next_output_byte = cinfo->dest->next_output_byte;
475 entropy->free_in_buffer = cinfo->dest->free_in_buffer;
476
477 /* Emit restart marker if needed */
478 if (cinfo->restart_interval)
479 if (entropy->restarts_to_go == 0)
480 emit_restart(entropy, entropy->next_restart_num);
481
482 /* Encode the MCU data block */
483 block = MCU_data[0];
484
485 /* Encode the AC coefficients per section G.1.2.2, fig. G.3 */
486
487 r = 0; /* r = run length of zeros */
488
489 for (k = cinfo->Ss; k <= Se; k++) {
490 if ((temp = (*block)[jpeg_natural_order[k]]) == 0) {
491 r++;
492 continue;
493 }
494 /* We must apply the point transform by Al. For AC coefficients this
495 * is an integer division with rounding towards 0. To do this portably
496 * in C, we shift after obtaining the absolute value; so the code is
497 * interwoven with finding the abs value (temp) and output bits (temp2).
498 */
499 if (temp < 0) {
500 temp = -temp; /* temp is abs value of input */
501 temp >>= Al; /* apply the point transform */
502 /* For a negative coef, want temp2 = bitwise complement of abs(coef) */
503 temp2 = ~temp;
504 } else {
505 temp >>= Al; /* apply the point transform */
506 temp2 = temp;
507 }
508 /* Watch out for case that nonzero coef is zero after point transform */
509 if (temp == 0) {
510 r++;
511 continue;
512 }
513
514 /* Emit any pending EOBRUN */
515 if (entropy->EOBRUN > 0)
516 emit_eobrun(entropy);
517 /* if run length > 15, must emit special run-length-16 codes (0xF0) */
518 while (r > 15) {
519 emit_symbol(entropy, entropy->ac_tbl_no, 0xF0);
520 r -= 16;
521 }
522
523 /* Find the number of bits needed for the magnitude of the coefficient */
524 nbits = 1; /* there must be at least one 1 bit */
525 while ((temp >>= 1))
526 nbits++;
527 /* Check for out-of-range coefficient values */
528 if (nbits > MAX_COEF_BITS)
529 ERREXIT(cinfo, JERR_BAD_DCT_COEF);
530
531 /* Count/emit Huffman symbol for run length / number of bits */
532 emit_symbol(entropy, entropy->ac_tbl_no, (r << 4) + nbits);
533
534 /* Emit that number of bits of the value, if positive, */
535 /* or the complement of its magnitude, if negative. */
536 emit_bits(entropy, (unsigned int) temp2, nbits);
537
538 r = 0; /* reset zero run length */
539 }
540
541 if (r > 0) { /* If there are trailing zeroes, */
542 entropy->EOBRUN++; /* count an EOB */
543 if (entropy->EOBRUN == 0x7FFF)
544 emit_eobrun(entropy); /* force it out to avoid overflow */
545 }
546
547 cinfo->dest->next_output_byte = entropy->next_output_byte;
548 cinfo->dest->free_in_buffer = entropy->free_in_buffer;
549
550 /* Update restart-interval state too */
551 if (cinfo->restart_interval) {
552 if (entropy->restarts_to_go == 0) {
553 entropy->restarts_to_go = cinfo->restart_interval;
554 entropy->next_restart_num++;
555 entropy->next_restart_num &= 7;
556 }
557 entropy->restarts_to_go--;
558 }
559
560 return TRUE;
561 }
562
563
564 /*
565 * MCU encoding for DC successive approximation refinement scan.
566 * Note: we assume such scans can be multi-component, although the spec
567 * is not very clear on the point.
568 */
569
570 METHODDEF(boolean)
encode_mcu_DC_refine(j_compress_ptr cinfo,JBLOCKROW * MCU_data)571 encode_mcu_DC_refine (j_compress_ptr cinfo, JBLOCKROW *MCU_data)
572 {
573 phuff_entropy_ptr entropy = (phuff_entropy_ptr) cinfo->entropy;
574 register int temp;
575 int blkn;
576 int Al = cinfo->Al;
577 JBLOCKROW block;
578
579 entropy->next_output_byte = cinfo->dest->next_output_byte;
580 entropy->free_in_buffer = cinfo->dest->free_in_buffer;
581
582 /* Emit restart marker if needed */
583 if (cinfo->restart_interval)
584 if (entropy->restarts_to_go == 0)
585 emit_restart(entropy, entropy->next_restart_num);
586
587 /* Encode the MCU data blocks */
588 for (blkn = 0; blkn < cinfo->blocks_in_MCU; blkn++) {
589 block = MCU_data[blkn];
590
591 /* We simply emit the Al'th bit of the DC coefficient value. */
592 temp = (*block)[0];
593 emit_bits(entropy, (unsigned int) (temp >> Al), 1);
594 }
595
596 cinfo->dest->next_output_byte = entropy->next_output_byte;
597 cinfo->dest->free_in_buffer = entropy->free_in_buffer;
598
599 /* Update restart-interval state too */
600 if (cinfo->restart_interval) {
601 if (entropy->restarts_to_go == 0) {
602 entropy->restarts_to_go = cinfo->restart_interval;
603 entropy->next_restart_num++;
604 entropy->next_restart_num &= 7;
605 }
606 entropy->restarts_to_go--;
607 }
608
609 return TRUE;
610 }
611
612
613 /*
614 * MCU encoding for AC successive approximation refinement scan.
615 */
616
617 METHODDEF(boolean)
encode_mcu_AC_refine(j_compress_ptr cinfo,JBLOCKROW * MCU_data)618 encode_mcu_AC_refine (j_compress_ptr cinfo, JBLOCKROW *MCU_data)
619 {
620 phuff_entropy_ptr entropy = (phuff_entropy_ptr) cinfo->entropy;
621 register int temp;
622 register int r, k;
623 int EOB;
624 char *BR_buffer;
625 unsigned int BR;
626 int Se = cinfo->Se;
627 int Al = cinfo->Al;
628 JBLOCKROW block;
629 int absvalues[DCTSIZE2];
630
631 entropy->next_output_byte = cinfo->dest->next_output_byte;
632 entropy->free_in_buffer = cinfo->dest->free_in_buffer;
633
634 /* Emit restart marker if needed */
635 if (cinfo->restart_interval)
636 if (entropy->restarts_to_go == 0)
637 emit_restart(entropy, entropy->next_restart_num);
638
639 /* Encode the MCU data block */
640 block = MCU_data[0];
641
642 /* It is convenient to make a pre-pass to determine the transformed
643 * coefficients' absolute values and the EOB position.
644 */
645 EOB = 0;
646 for (k = cinfo->Ss; k <= Se; k++) {
647 temp = (*block)[jpeg_natural_order[k]];
648 /* We must apply the point transform by Al. For AC coefficients this
649 * is an integer division with rounding towards 0. To do this portably
650 * in C, we shift after obtaining the absolute value.
651 */
652 if (temp < 0)
653 temp = -temp; /* temp is abs value of input */
654 temp >>= Al; /* apply the point transform */
655 absvalues[k] = temp; /* save abs value for main pass */
656 if (temp == 1)
657 EOB = k; /* EOB = index of last newly-nonzero coef */
658 }
659
660 /* Encode the AC coefficients per section G.1.2.3, fig. G.7 */
661
662 r = 0; /* r = run length of zeros */
663 BR = 0; /* BR = count of buffered bits added now */
664 BR_buffer = entropy->bit_buffer + entropy->BE; /* Append bits to buffer */
665
666 for (k = cinfo->Ss; k <= Se; k++) {
667 if ((temp = absvalues[k]) == 0) {
668 r++;
669 continue;
670 }
671
672 /* Emit any required ZRLs, but not if they can be folded into EOB */
673 while (r > 15 && k <= EOB) {
674 /* emit any pending EOBRUN and the BE correction bits */
675 emit_eobrun(entropy);
676 /* Emit ZRL */
677 emit_symbol(entropy, entropy->ac_tbl_no, 0xF0);
678 r -= 16;
679 /* Emit buffered correction bits that must be associated with ZRL */
680 emit_buffered_bits(entropy, BR_buffer, BR);
681 BR_buffer = entropy->bit_buffer; /* BE bits are gone now */
682 BR = 0;
683 }
684
685 /* If the coef was previously nonzero, it only needs a correction bit.
686 * NOTE: a straight translation of the spec's figure G.7 would suggest
687 * that we also need to test r > 15. But if r > 15, we can only get here
688 * if k > EOB, which implies that this coefficient is not 1.
689 */
690 if (temp > 1) {
691 /* The correction bit is the next bit of the absolute value. */
692 BR_buffer[BR++] = (char) (temp & 1);
693 continue;
694 }
695
696 /* Emit any pending EOBRUN and the BE correction bits */
697 emit_eobrun(entropy);
698
699 /* Count/emit Huffman symbol for run length / number of bits */
700 emit_symbol(entropy, entropy->ac_tbl_no, (r << 4) + 1);
701
702 /* Emit output bit for newly-nonzero coef */
703 temp = ((*block)[jpeg_natural_order[k]] < 0) ? 0 : 1;
704 emit_bits(entropy, (unsigned int) temp, 1);
705
706 /* Emit buffered correction bits that must be associated with this code */
707 emit_buffered_bits(entropy, BR_buffer, BR);
708 BR_buffer = entropy->bit_buffer; /* BE bits are gone now */
709 BR = 0;
710 r = 0; /* reset zero run length */
711 }
712
713 if (r > 0 || BR > 0) { /* If there are trailing zeroes, */
714 entropy->EOBRUN++; /* count an EOB */
715 entropy->BE += BR; /* concat my correction bits to older ones */
716 /* We force out the EOB if we risk either:
717 * 1. overflow of the EOB counter;
718 * 2. overflow of the correction bit buffer during the next MCU.
719 */
720 if (entropy->EOBRUN == 0x7FFF || entropy->BE > (MAX_CORR_BITS-DCTSIZE2+1))
721 emit_eobrun(entropy);
722 }
723
724 cinfo->dest->next_output_byte = entropy->next_output_byte;
725 cinfo->dest->free_in_buffer = entropy->free_in_buffer;
726
727 /* Update restart-interval state too */
728 if (cinfo->restart_interval) {
729 if (entropy->restarts_to_go == 0) {
730 entropy->restarts_to_go = cinfo->restart_interval;
731 entropy->next_restart_num++;
732 entropy->next_restart_num &= 7;
733 }
734 entropy->restarts_to_go--;
735 }
736
737 return TRUE;
738 }
739
740
741 /*
742 * Finish up at the end of a Huffman-compressed progressive scan.
743 */
744
745 METHODDEF(void)
finish_pass_phuff(j_compress_ptr cinfo)746 finish_pass_phuff (j_compress_ptr cinfo)
747 {
748 phuff_entropy_ptr entropy = (phuff_entropy_ptr) cinfo->entropy;
749
750 entropy->next_output_byte = cinfo->dest->next_output_byte;
751 entropy->free_in_buffer = cinfo->dest->free_in_buffer;
752
753 /* Flush out any buffered data */
754 emit_eobrun(entropy);
755 flush_bits(entropy);
756
757 cinfo->dest->next_output_byte = entropy->next_output_byte;
758 cinfo->dest->free_in_buffer = entropy->free_in_buffer;
759 }
760
761
762 /*
763 * Finish up a statistics-gathering pass and create the new Huffman tables.
764 */
765
766 METHODDEF(void)
finish_pass_gather_phuff(j_compress_ptr cinfo)767 finish_pass_gather_phuff (j_compress_ptr cinfo)
768 {
769 phuff_entropy_ptr entropy = (phuff_entropy_ptr) cinfo->entropy;
770 boolean is_DC_band;
771 int ci, tbl;
772 jpeg_component_info * compptr;
773 JHUFF_TBL **htblptr;
774 boolean did[NUM_HUFF_TBLS];
775
776 /* Flush out buffered data (all we care about is counting the EOB symbol) */
777 emit_eobrun(entropy);
778
779 is_DC_band = (cinfo->Ss == 0);
780
781 /* It's important not to apply jpeg_gen_optimal_table more than once
782 * per table, because it clobbers the input frequency counts!
783 */
784 MEMZERO(did, SIZEOF(did));
785
786 for (ci = 0; ci < cinfo->comps_in_scan; ci++) {
787 compptr = cinfo->cur_comp_info[ci];
788 if (is_DC_band) {
789 if (cinfo->Ah != 0) /* DC refinement needs no table */
790 continue;
791 tbl = compptr->dc_tbl_no;
792 } else {
793 tbl = compptr->ac_tbl_no;
794 }
795 if (! did[tbl]) {
796 if (is_DC_band)
797 htblptr = & cinfo->dc_huff_tbl_ptrs[tbl];
798 else
799 htblptr = & cinfo->ac_huff_tbl_ptrs[tbl];
800 if (*htblptr == NULL)
801 *htblptr = jpeg_alloc_huff_table((j_common_ptr) cinfo);
802 jpeg_gen_optimal_table(cinfo, *htblptr, entropy->count_ptrs[tbl]);
803 did[tbl] = TRUE;
804 }
805 }
806 }
807
808
809 /*
810 * Module initialization routine for progressive Huffman entropy encoding.
811 */
812
813 GLOBAL(void)
jinit_phuff_encoder(j_compress_ptr cinfo)814 jinit_phuff_encoder (j_compress_ptr cinfo)
815 {
816 phuff_entropy_ptr entropy;
817 int i;
818
819 entropy = (phuff_entropy_ptr)
820 (*cinfo->mem->alloc_small) ((j_common_ptr) cinfo, JPOOL_IMAGE,
821 SIZEOF(phuff_entropy_encoder));
822 cinfo->entropy = (struct jpeg_entropy_encoder *) entropy;
823 entropy->pub.start_pass = start_pass_phuff;
824
825 /* Mark tables unallocated */
826 for (i = 0; i < NUM_HUFF_TBLS; i++) {
827 entropy->derived_tbls[i] = NULL;
828 entropy->count_ptrs[i] = NULL;
829 }
830 entropy->bit_buffer = NULL; /* needed only in AC refinement scan */
831 }
832
833 #endif /* C_PROGRESSIVE_SUPPORTED */
834