1 /*
2 * jcphuff.c
3 *
4 * Copyright (C) 1995-1998, 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 "jlossy.h" /* Private declarations for lossy codec */
19 #include "jchuff.h" /* Declarations shared with jc*huff.c */
20
21 #ifdef C_PROGRESSIVE_SUPPORTED
22
23 /* Expanded entropy encoder object for progressive Huffman encoding. */
24
25 typedef struct {
26 /* Mode flag: TRUE for optimization, FALSE for actual data output */
27 boolean gather_statistics;
28
29 /* Bit-level coding status.
30 * next_output_byte/free_in_buffer are local copies of cinfo->dest fields.
31 */
32 JOCTET * next_output_byte; /* => next byte to write in buffer */
33 size_t free_in_buffer; /* # of byte spaces remaining in buffer */
34 INT32 put_buffer; /* current bit-accumulation buffer */
35 int put_bits; /* # of bits now in it */
36 j_compress_ptr cinfo; /* link to cinfo (needed for dump_buffer) */
37
38 /* Coding status for DC components */
39 int last_dc_val[MAX_COMPS_IN_SCAN]; /* last DC coef for each component */
40
41 /* Coding status for AC components */
42 int ac_tbl_no; /* the table number of the single component */
43 unsigned int EOBRUN; /* run length of EOBs */
44 unsigned int BE; /* # of buffered correction bits before MCU */
45 char * bit_buffer; /* buffer for correction bits (1 per char) */
46 /* packing correction bits tightly would save some space but cost time... */
47
48 unsigned int restarts_to_go; /* MCUs left in this restart interval */
49 int next_restart_num; /* next restart number to write (0-7) */
50
51 /* Pointers to derived tables (these workspaces have image lifespan).
52 * Since any one scan codes only DC or only AC, we only need one set
53 * of tables, not one for DC and one for AC.
54 */
55 c_derived_tbl * derived_tbls[NUM_HUFF_TBLS];
56
57 /* Statistics tables for optimization; again, one set is enough */
58 long * count_ptrs[NUM_HUFF_TBLS];
59 } phuff_entropy_encoder;
60
61 typedef phuff_entropy_encoder * phuff_entropy_ptr;
62
63 /* MAX_CORR_BITS is the number of bits the AC refinement correction-bit
64 * buffer can hold. Larger sizes may slightly improve compression, but
65 * 1000 is already well into the realm of overkill.
66 * The minimum safe size is 64 bits.
67 */
68
69 #define MAX_CORR_BITS 1000 /* Max # of correction bits I can buffer */
70
71 /* IRIGHT_SHIFT is like RIGHT_SHIFT, but works on int rather than INT32.
72 * We assume that int right shift is unsigned if INT32 right shift is,
73 * which should be safe.
74 */
75
76 #ifdef RIGHT_SHIFT_IS_UNSIGNED
77 #define ISHIFT_TEMPS int ishift_temp;
78 #define IRIGHT_SHIFT(x,shft) \
79 ((ishift_temp = (x)) < 0 ? \
80 (ishift_temp >> (shft)) | ((~0) << (16-(shft))) : \
81 (ishift_temp >> (shft)))
82 #else
83 #define ISHIFT_TEMPS
84 #define IRIGHT_SHIFT(x,shft) ((x) >> (shft))
85 #endif
86
87 /* Forward declarations */
88 METHODDEF(boolean) encode_mcu_DC_first JPP((j_compress_ptr cinfo,
89 JBLOCKROW *MCU_data));
90 METHODDEF(boolean) encode_mcu_AC_first JPP((j_compress_ptr cinfo,
91 JBLOCKROW *MCU_data));
92 METHODDEF(boolean) encode_mcu_DC_refine JPP((j_compress_ptr cinfo,
93 JBLOCKROW *MCU_data));
94 METHODDEF(boolean) encode_mcu_AC_refine JPP((j_compress_ptr cinfo,
95 JBLOCKROW *MCU_data));
96 METHODDEF(void) finish_pass_phuff JPP((j_compress_ptr cinfo));
97 METHODDEF(void) finish_pass_gather_phuff JPP((j_compress_ptr cinfo));
98
99
100 /*
101 * Initialize for a Huffman-compressed scan using progressive JPEG.
102 */
103
104 METHODDEF(void)
start_pass_phuff(j_compress_ptr cinfo,boolean gather_statistics)105 start_pass_phuff (j_compress_ptr cinfo, boolean gather_statistics)
106 {
107 j_lossy_c_ptr lossyc = (j_lossy_c_ptr) cinfo->codec;
108 phuff_entropy_ptr entropy = (phuff_entropy_ptr) lossyc->entropy_private;
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 lossyc->entropy_encode_mcu = encode_mcu_DC_first;
124 else
125 lossyc->entropy_encode_mcu = encode_mcu_AC_first;
126 } else {
127 if (is_DC_band)
128 lossyc->entropy_encode_mcu = encode_mcu_DC_refine;
129 else {
130 lossyc->entropy_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 lossyc->pub.entropy_finish_pass = finish_pass_gather_phuff;
140 else
141 lossyc->pub.entropy_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 j_lossy_c_ptr lossyc = (j_lossy_c_ptr) cinfo->codec;
380 phuff_entropy_ptr entropy = (phuff_entropy_ptr) lossyc->entropy_private;
381 register int temp, temp2;
382 register int nbits;
383 int blkn, ci;
384 int Al = cinfo->Al;
385 JBLOCKROW block;
386 jpeg_component_info * compptr;
387 ISHIFT_TEMPS
388
389 entropy->next_output_byte = cinfo->dest->next_output_byte;
390 entropy->free_in_buffer = cinfo->dest->free_in_buffer;
391
392 /* Emit restart marker if needed */
393 if (cinfo->restart_interval)
394 if (entropy->restarts_to_go == 0)
395 emit_restart(entropy, entropy->next_restart_num);
396
397 /* Encode the MCU data blocks */
398 for (blkn = 0; blkn < cinfo->data_units_in_MCU; blkn++) {
399 block = MCU_data[blkn];
400 ci = cinfo->MCU_membership[blkn];
401 compptr = cinfo->cur_comp_info[ci];
402
403 /* Compute the DC value after the required point transform by Al.
404 * This is simply an arithmetic right shift.
405 */
406 temp2 = IRIGHT_SHIFT((int) ((*block)[0]), Al);
407
408 /* DC differences are figured on the point-transformed values. */
409 temp = temp2 - entropy->last_dc_val[ci];
410 entropy->last_dc_val[ci] = temp2;
411
412 /* Encode the DC coefficient difference per section G.1.2.1 */
413 temp2 = temp;
414 if (temp < 0) {
415 temp = -temp; /* temp is abs value of input */
416 /* For a negative input, want temp2 = bitwise complement of abs(input) */
417 /* This code assumes we are on a two's complement machine */
418 temp2--;
419 }
420
421 /* Find the number of bits needed for the magnitude of the coefficient */
422 nbits = 0;
423 while (temp) {
424 nbits++;
425 temp >>= 1;
426 }
427 /* Check for out-of-range coefficient values.
428 * Since we're encoding a difference, the range limit is twice as much.
429 */
430 if (nbits > MAX_COEF_BITS+1)
431 ERREXIT(cinfo, JERR_BAD_DCT_COEF);
432
433 /* Count/emit the Huffman-coded symbol for the number of bits */
434 emit_symbol(entropy, compptr->dc_tbl_no, nbits);
435
436 /* Emit that number of bits of the value, if positive, */
437 /* or the complement of its magnitude, if negative. */
438 if (nbits) /* emit_bits rejects calls with size 0 */
439 emit_bits(entropy, (unsigned int) temp2, nbits);
440 }
441
442 cinfo->dest->next_output_byte = entropy->next_output_byte;
443 cinfo->dest->free_in_buffer = entropy->free_in_buffer;
444
445 /* Update restart-interval state too */
446 if (cinfo->restart_interval) {
447 if (entropy->restarts_to_go == 0) {
448 entropy->restarts_to_go = cinfo->restart_interval;
449 entropy->next_restart_num++;
450 entropy->next_restart_num &= 7;
451 }
452 entropy->restarts_to_go--;
453 }
454
455 return TRUE;
456 }
457
458
459 /*
460 * MCU encoding for AC initial scan (either spectral selection,
461 * or first pass of successive approximation).
462 */
463
464 METHODDEF(boolean)
encode_mcu_AC_first(j_compress_ptr cinfo,JBLOCKROW * MCU_data)465 encode_mcu_AC_first (j_compress_ptr cinfo, JBLOCKROW *MCU_data)
466 {
467 j_lossy_c_ptr lossyc = (j_lossy_c_ptr) cinfo->codec;
468 phuff_entropy_ptr entropy = (phuff_entropy_ptr) lossyc->entropy_private;
469 register int temp, temp2;
470 register int nbits;
471 register int r, k;
472 int Se = cinfo->Se;
473 int Al = cinfo->Al;
474 JBLOCKROW block;
475
476 entropy->next_output_byte = cinfo->dest->next_output_byte;
477 entropy->free_in_buffer = cinfo->dest->free_in_buffer;
478
479 /* Emit restart marker if needed */
480 if (cinfo->restart_interval)
481 if (entropy->restarts_to_go == 0)
482 emit_restart(entropy, entropy->next_restart_num);
483
484 /* Encode the MCU data block */
485 block = MCU_data[0];
486
487 /* Encode the AC coefficients per section G.1.2.2, fig. G.3 */
488
489 r = 0; /* r = run length of zeros */
490
491 for (k = cinfo->Ss; k <= Se; k++) {
492 if ((temp = (*block)[jpeg_natural_order[k]]) == 0) {
493 r++;
494 continue;
495 }
496 /* We must apply the point transform by Al. For AC coefficients this
497 * is an integer division with rounding towards 0. To do this portably
498 * in C, we shift after obtaining the absolute value; so the code is
499 * interwoven with finding the abs value (temp) and output bits (temp2).
500 */
501 if (temp < 0) {
502 temp = -temp; /* temp is abs value of input */
503 temp >>= Al; /* apply the point transform */
504 /* For a negative coef, want temp2 = bitwise complement of abs(coef) */
505 temp2 = ~temp;
506 } else {
507 temp >>= Al; /* apply the point transform */
508 temp2 = temp;
509 }
510 /* Watch out for case that nonzero coef is zero after point transform */
511 if (temp == 0) {
512 r++;
513 continue;
514 }
515
516 /* Emit any pending EOBRUN */
517 if (entropy->EOBRUN > 0)
518 emit_eobrun(entropy);
519 /* if run length > 15, must emit special run-length-16 codes (0xF0) */
520 while (r > 15) {
521 emit_symbol(entropy, entropy->ac_tbl_no, 0xF0);
522 r -= 16;
523 }
524
525 /* Find the number of bits needed for the magnitude of the coefficient */
526 nbits = 1; /* there must be at least one 1 bit */
527 while ((temp >>= 1))
528 nbits++;
529 /* Check for out-of-range coefficient values */
530 if (nbits > MAX_COEF_BITS)
531 ERREXIT(cinfo, JERR_BAD_DCT_COEF);
532
533 /* Count/emit Huffman symbol for run length / number of bits */
534 emit_symbol(entropy, entropy->ac_tbl_no, (r << 4) + nbits);
535
536 /* Emit that number of bits of the value, if positive, */
537 /* or the complement of its magnitude, if negative. */
538 emit_bits(entropy, (unsigned int) temp2, nbits);
539
540 r = 0; /* reset zero run length */
541 }
542
543 if (r > 0) { /* If there are trailing zeroes, */
544 entropy->EOBRUN++; /* count an EOB */
545 if (entropy->EOBRUN == 0x7FFF)
546 emit_eobrun(entropy); /* force it out to avoid overflow */
547 }
548
549 cinfo->dest->next_output_byte = entropy->next_output_byte;
550 cinfo->dest->free_in_buffer = entropy->free_in_buffer;
551
552 /* Update restart-interval state too */
553 if (cinfo->restart_interval) {
554 if (entropy->restarts_to_go == 0) {
555 entropy->restarts_to_go = cinfo->restart_interval;
556 entropy->next_restart_num++;
557 entropy->next_restart_num &= 7;
558 }
559 entropy->restarts_to_go--;
560 }
561
562 return TRUE;
563 }
564
565
566 /*
567 * MCU encoding for DC successive approximation refinement scan.
568 * Note: we assume such scans can be multi-component, although the spec
569 * is not very clear on the point.
570 */
571
572 METHODDEF(boolean)
encode_mcu_DC_refine(j_compress_ptr cinfo,JBLOCKROW * MCU_data)573 encode_mcu_DC_refine (j_compress_ptr cinfo, JBLOCKROW *MCU_data)
574 {
575 j_lossy_c_ptr lossyc = (j_lossy_c_ptr) cinfo->codec;
576 phuff_entropy_ptr entropy = (phuff_entropy_ptr) lossyc->entropy_private;
577 register int temp;
578 int blkn;
579 int Al = cinfo->Al;
580 JBLOCKROW block;
581
582 entropy->next_output_byte = cinfo->dest->next_output_byte;
583 entropy->free_in_buffer = cinfo->dest->free_in_buffer;
584
585 /* Emit restart marker if needed */
586 if (cinfo->restart_interval)
587 if (entropy->restarts_to_go == 0)
588 emit_restart(entropy, entropy->next_restart_num);
589
590 /* Encode the MCU data blocks */
591 for (blkn = 0; blkn < cinfo->data_units_in_MCU; blkn++) {
592 block = MCU_data[blkn];
593
594 /* We simply emit the Al'th bit of the DC coefficient value. */
595 temp = (*block)[0];
596 emit_bits(entropy, (unsigned int) (temp >> Al), 1);
597 }
598
599 cinfo->dest->next_output_byte = entropy->next_output_byte;
600 cinfo->dest->free_in_buffer = entropy->free_in_buffer;
601
602 /* Update restart-interval state too */
603 if (cinfo->restart_interval) {
604 if (entropy->restarts_to_go == 0) {
605 entropy->restarts_to_go = cinfo->restart_interval;
606 entropy->next_restart_num++;
607 entropy->next_restart_num &= 7;
608 }
609 entropy->restarts_to_go--;
610 }
611
612 return TRUE;
613 }
614
615
616 /*
617 * MCU encoding for AC successive approximation refinement scan.
618 */
619
620 METHODDEF(boolean)
encode_mcu_AC_refine(j_compress_ptr cinfo,JBLOCKROW * MCU_data)621 encode_mcu_AC_refine (j_compress_ptr cinfo, JBLOCKROW *MCU_data)
622 {
623 j_lossy_c_ptr lossyc = (j_lossy_c_ptr) cinfo->codec;
624 phuff_entropy_ptr entropy = (phuff_entropy_ptr) lossyc->entropy_private;
625 register int temp;
626 register int r, k;
627 int EOB;
628 char *BR_buffer;
629 unsigned int BR;
630 int Se = cinfo->Se;
631 int Al = cinfo->Al;
632 JBLOCKROW block;
633 int absvalues[DCTSIZE2];
634
635 entropy->next_output_byte = cinfo->dest->next_output_byte;
636 entropy->free_in_buffer = cinfo->dest->free_in_buffer;
637
638 /* Emit restart marker if needed */
639 if (cinfo->restart_interval)
640 if (entropy->restarts_to_go == 0)
641 emit_restart(entropy, entropy->next_restart_num);
642
643 /* Encode the MCU data block */
644 block = MCU_data[0];
645
646 /* It is convenient to make a pre-pass to determine the transformed
647 * coefficients' absolute values and the EOB position.
648 */
649 EOB = 0;
650 for (k = cinfo->Ss; k <= Se; k++) {
651 temp = (*block)[jpeg_natural_order[k]];
652 /* We must apply the point transform by Al. For AC coefficients this
653 * is an integer division with rounding towards 0. To do this portably
654 * in C, we shift after obtaining the absolute value.
655 */
656 if (temp < 0)
657 temp = -temp; /* temp is abs value of input */
658 temp >>= Al; /* apply the point transform */
659 absvalues[k] = temp; /* save abs value for main pass */
660 if (temp == 1)
661 EOB = k; /* EOB = index of last newly-nonzero coef */
662 }
663
664 /* Encode the AC coefficients per section G.1.2.3, fig. G.7 */
665
666 r = 0; /* r = run length of zeros */
667 BR = 0; /* BR = count of buffered bits added now */
668 BR_buffer = entropy->bit_buffer + entropy->BE; /* Append bits to buffer */
669
670 for (k = cinfo->Ss; k <= Se; k++) {
671 if ((temp = absvalues[k]) == 0) {
672 r++;
673 continue;
674 }
675
676 /* Emit any required ZRLs, but not if they can be folded into EOB */
677 while (r > 15 && k <= EOB) {
678 /* emit any pending EOBRUN and the BE correction bits */
679 emit_eobrun(entropy);
680 /* Emit ZRL */
681 emit_symbol(entropy, entropy->ac_tbl_no, 0xF0);
682 r -= 16;
683 /* Emit buffered correction bits that must be associated with ZRL */
684 emit_buffered_bits(entropy, BR_buffer, BR);
685 BR_buffer = entropy->bit_buffer; /* BE bits are gone now */
686 BR = 0;
687 }
688
689 /* If the coef was previously nonzero, it only needs a correction bit.
690 * NOTE: a straight translation of the spec's figure G.7 would suggest
691 * that we also need to test r > 15. But if r > 15, we can only get here
692 * if k > EOB, which implies that this coefficient is not 1.
693 */
694 if (temp > 1) {
695 /* The correction bit is the next bit of the absolute value. */
696 BR_buffer[BR++] = (char) (temp & 1);
697 continue;
698 }
699
700 /* Emit any pending EOBRUN and the BE correction bits */
701 emit_eobrun(entropy);
702
703 /* Count/emit Huffman symbol for run length / number of bits */
704 emit_symbol(entropy, entropy->ac_tbl_no, (r << 4) + 1);
705
706 /* Emit output bit for newly-nonzero coef */
707 temp = ((*block)[jpeg_natural_order[k]] < 0) ? 0 : 1;
708 emit_bits(entropy, (unsigned int) temp, 1);
709
710 /* Emit buffered correction bits that must be associated with this code */
711 emit_buffered_bits(entropy, BR_buffer, BR);
712 BR_buffer = entropy->bit_buffer; /* BE bits are gone now */
713 BR = 0;
714 r = 0; /* reset zero run length */
715 }
716
717 if (r > 0 || BR > 0) { /* If there are trailing zeroes, */
718 entropy->EOBRUN++; /* count an EOB */
719 entropy->BE += BR; /* concat my correction bits to older ones */
720 /* We force out the EOB if we risk either:
721 * 1. overflow of the EOB counter;
722 * 2. overflow of the correction bit buffer during the next MCU.
723 */
724 if (entropy->EOBRUN == 0x7FFF || entropy->BE > (MAX_CORR_BITS-DCTSIZE2+1))
725 emit_eobrun(entropy);
726 }
727
728 cinfo->dest->next_output_byte = entropy->next_output_byte;
729 cinfo->dest->free_in_buffer = entropy->free_in_buffer;
730
731 /* Update restart-interval state too */
732 if (cinfo->restart_interval) {
733 if (entropy->restarts_to_go == 0) {
734 entropy->restarts_to_go = cinfo->restart_interval;
735 entropy->next_restart_num++;
736 entropy->next_restart_num &= 7;
737 }
738 entropy->restarts_to_go--;
739 }
740
741 return TRUE;
742 }
743
744
745 /*
746 * Finish up at the end of a Huffman-compressed progressive scan.
747 */
748
749 METHODDEF(void)
finish_pass_phuff(j_compress_ptr cinfo)750 finish_pass_phuff (j_compress_ptr cinfo)
751 {
752 j_lossy_c_ptr lossyc = (j_lossy_c_ptr) cinfo->codec;
753 phuff_entropy_ptr entropy = (phuff_entropy_ptr) lossyc->entropy_private;
754
755 entropy->next_output_byte = cinfo->dest->next_output_byte;
756 entropy->free_in_buffer = cinfo->dest->free_in_buffer;
757
758 /* Flush out any buffered data */
759 emit_eobrun(entropy);
760 flush_bits(entropy);
761
762 cinfo->dest->next_output_byte = entropy->next_output_byte;
763 cinfo->dest->free_in_buffer = entropy->free_in_buffer;
764 }
765
766
767 /*
768 * Finish up a statistics-gathering pass and create the new Huffman tables.
769 */
770
771 METHODDEF(void)
finish_pass_gather_phuff(j_compress_ptr cinfo)772 finish_pass_gather_phuff (j_compress_ptr cinfo)
773 {
774 j_lossy_c_ptr lossyc = (j_lossy_c_ptr) cinfo->codec;
775 phuff_entropy_ptr entropy = (phuff_entropy_ptr) lossyc->entropy_private;
776 boolean is_DC_band;
777 int ci, tbl;
778 jpeg_component_info * compptr;
779 JHUFF_TBL **htblptr;
780 boolean did[NUM_HUFF_TBLS];
781
782 /* Flush out buffered data (all we care about is counting the EOB symbol) */
783 emit_eobrun(entropy);
784
785 is_DC_band = (cinfo->Ss == 0);
786
787 /* It's important not to apply jpeg_gen_optimal_table more than once
788 * per table, because it clobbers the input frequency counts!
789 */
790 MEMZERO(did, SIZEOF(did));
791
792 for (ci = 0; ci < cinfo->comps_in_scan; ci++) {
793 compptr = cinfo->cur_comp_info[ci];
794 if (is_DC_band) {
795 if (cinfo->Ah != 0) /* DC refinement needs no table */
796 continue;
797 tbl = compptr->dc_tbl_no;
798 } else {
799 tbl = compptr->ac_tbl_no;
800 }
801 if (! did[tbl]) {
802 if (is_DC_band)
803 htblptr = & cinfo->dc_huff_tbl_ptrs[tbl];
804 else
805 htblptr = & cinfo->ac_huff_tbl_ptrs[tbl];
806 if (*htblptr == NULL)
807 *htblptr = jpeg_alloc_huff_table((j_common_ptr) cinfo);
808 jpeg_gen_optimal_table(cinfo, *htblptr, entropy->count_ptrs[tbl]);
809 did[tbl] = TRUE;
810 }
811 }
812 }
813
814
815 METHODDEF(boolean)
need_optimization_pass(j_compress_ptr cinfo)816 need_optimization_pass (j_compress_ptr cinfo)
817 {
818 return (cinfo->Ss != 0 || cinfo->Ah == 0);
819 }
820
821
822 /*
823 * Module initialization routine for progressive Huffman entropy encoding.
824 */
825
826 GLOBAL(void)
jinit_phuff_encoder(j_compress_ptr cinfo)827 jinit_phuff_encoder (j_compress_ptr cinfo)
828 {
829 j_lossy_c_ptr lossyc = (j_lossy_c_ptr) cinfo->codec;
830 phuff_entropy_ptr entropy;
831 int i;
832
833 entropy = (phuff_entropy_ptr)
834 (*cinfo->mem->alloc_small) ((j_common_ptr) cinfo, JPOOL_IMAGE,
835 SIZEOF(phuff_entropy_encoder));
836 lossyc->entropy_private = (struct jpeg_entropy_encoder *) entropy;
837 lossyc->pub.entropy_start_pass = start_pass_phuff;
838 lossyc->pub.need_optimization_pass = need_optimization_pass;
839
840 /* Mark tables unallocated */
841 for (i = 0; i < NUM_HUFF_TBLS; i++) {
842 entropy->derived_tbls[i] = NULL;
843 entropy->count_ptrs[i] = NULL;
844 }
845 entropy->bit_buffer = NULL; /* needed only in AC refinement scan */
846 }
847
848 #endif /* C_PROGRESSIVE_SUPPORTED */
849