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Thomas G. Lanebc79e061995-08-02 00:00:00 +00001/*
2 * jcphuff.c
3 *
Thomas G. Lane5ead57a1998-03-27 00:00:00 +00004 * Copyright (C) 1995-1997, Thomas G. Lane.
Thomas G. Lanebc79e061995-08-02 00:00:00 +00005 * 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
24typedef 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
62typedef 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 */
Thomas G. Lane489583f1996-02-07 00:00:00 +000089METHODDEF(boolean) encode_mcu_DC_first JPP((j_compress_ptr cinfo,
Thomas G. Lanebc79e061995-08-02 00:00:00 +000090 JBLOCKROW *MCU_data));
Thomas G. Lane489583f1996-02-07 00:00:00 +000091METHODDEF(boolean) encode_mcu_AC_first JPP((j_compress_ptr cinfo,
Thomas G. Lanebc79e061995-08-02 00:00:00 +000092 JBLOCKROW *MCU_data));
Thomas G. Lane489583f1996-02-07 00:00:00 +000093METHODDEF(boolean) encode_mcu_DC_refine JPP((j_compress_ptr cinfo,
94 JBLOCKROW *MCU_data));
95METHODDEF(boolean) encode_mcu_AC_refine JPP((j_compress_ptr cinfo,
96 JBLOCKROW *MCU_data));
97METHODDEF(void) finish_pass_phuff JPP((j_compress_ptr cinfo));
98METHODDEF(void) finish_pass_gather_phuff JPP((j_compress_ptr cinfo));
Thomas G. Lanebc79e061995-08-02 00:00:00 +000099
100
101/*
102 * Initialize for a Huffman-compressed scan using progressive JPEG.
103 */
104
Thomas G. Lane489583f1996-02-07 00:00:00 +0000105METHODDEF(void)
Thomas G. Lanebc79e061995-08-02 00:00:00 +0000106start_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;
Thomas G. Lane5ead57a1998-03-27 00:00:00 +0000150 /* Get table index */
Thomas G. Lanebc79e061995-08-02 00:00:00 +0000151 if (is_DC_band) {
152 if (cinfo->Ah != 0) /* DC refinement needs no table */
153 continue;
154 tbl = compptr->dc_tbl_no;
Thomas G. Lanebc79e061995-08-02 00:00:00 +0000155 } else {
156 entropy->ac_tbl_no = tbl = compptr->ac_tbl_no;
Thomas G. Lanebc79e061995-08-02 00:00:00 +0000157 }
158 if (gather_statistics) {
Thomas G. Lane5ead57a1998-03-27 00:00:00 +0000159 /* 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);
Thomas G. Lanebc79e061995-08-02 00:00:00 +0000163 /* 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 {
Thomas G. Lane5ead57a1998-03-27 00:00:00 +0000171 /* Compute derived values for Huffman table */
Thomas G. Lanebc79e061995-08-02 00:00:00 +0000172 /* We may do this more than once for a table, but it's not expensive */
Thomas G. Lane5ead57a1998-03-27 00:00:00 +0000173 jpeg_make_c_derived_tbl(cinfo, is_DC_band, tbl,
174 & entropy->derived_tbls[tbl]);
Thomas G. Lanebc79e061995-08-02 00:00:00 +0000175 }
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
Thomas G. Lane489583f1996-02-07 00:00:00 +0000204LOCAL(void)
Thomas G. Lanebc79e061995-08-02 00:00:00 +0000205dump_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
Thomas G. Lane489583f1996-02-07 00:00:00 +0000226LOCAL(void)
Thomas G. Lanebc79e061995-08-02 00:00:00 +0000227emit_bits (phuff_entropy_ptr entropy, unsigned int code, int size)
228/* Emit some bits, unless we are in gather mode */
229{
230 /* This routine is heavily used, so it's worth coding tightly. */
231 register INT32 put_buffer = (INT32) code;
232 register int put_bits = entropy->put_bits;
233
234 /* if size is 0, caller used an invalid Huffman table entry */
235 if (size == 0)
236 ERREXIT(entropy->cinfo, JERR_HUFF_MISSING_CODE);
237
238 if (entropy->gather_statistics)
239 return; /* do nothing if we're only getting stats */
240
241 put_buffer &= (((INT32) 1)<<size) - 1; /* mask off any extra bits in code */
242
243 put_bits += size; /* new number of bits in buffer */
244
245 put_buffer <<= 24 - put_bits; /* align incoming bits */
246
247 put_buffer |= entropy->put_buffer; /* and merge with old buffer contents */
248
249 while (put_bits >= 8) {
250 int c = (int) ((put_buffer >> 16) & 0xFF);
251
252 emit_byte(entropy, c);
253 if (c == 0xFF) { /* need to stuff a zero byte? */
254 emit_byte(entropy, 0);
255 }
256 put_buffer <<= 8;
257 put_bits -= 8;
258 }
259
260 entropy->put_buffer = put_buffer; /* update variables */
261 entropy->put_bits = put_bits;
262}
263
264
Thomas G. Lane489583f1996-02-07 00:00:00 +0000265LOCAL(void)
Thomas G. Lanebc79e061995-08-02 00:00:00 +0000266flush_bits (phuff_entropy_ptr entropy)
267{
268 emit_bits(entropy, 0x7F, 7); /* fill any partial byte with ones */
269 entropy->put_buffer = 0; /* and reset bit-buffer to empty */
270 entropy->put_bits = 0;
271}
272
273
274/*
275 * Emit (or just count) a Huffman symbol.
276 */
277
Thomas G. Lane489583f1996-02-07 00:00:00 +0000278LOCAL(void)
Thomas G. Lanebc79e061995-08-02 00:00:00 +0000279emit_symbol (phuff_entropy_ptr entropy, int tbl_no, int symbol)
280{
281 if (entropy->gather_statistics)
282 entropy->count_ptrs[tbl_no][symbol]++;
283 else {
284 c_derived_tbl * tbl = entropy->derived_tbls[tbl_no];
285 emit_bits(entropy, tbl->ehufco[symbol], tbl->ehufsi[symbol]);
286 }
287}
288
289
290/*
291 * Emit bits from a correction bit buffer.
292 */
293
Thomas G. Lane489583f1996-02-07 00:00:00 +0000294LOCAL(void)
Thomas G. Lanebc79e061995-08-02 00:00:00 +0000295emit_buffered_bits (phuff_entropy_ptr entropy, char * bufstart,
296 unsigned int nbits)
297{
298 if (entropy->gather_statistics)
299 return; /* no real work */
300
301 while (nbits > 0) {
302 emit_bits(entropy, (unsigned int) (*bufstart), 1);
303 bufstart++;
304 nbits--;
305 }
306}
307
308
309/*
310 * Emit any pending EOBRUN symbol.
311 */
312
Thomas G. Lane489583f1996-02-07 00:00:00 +0000313LOCAL(void)
Thomas G. Lanebc79e061995-08-02 00:00:00 +0000314emit_eobrun (phuff_entropy_ptr entropy)
315{
316 register int temp, nbits;
317
318 if (entropy->EOBRUN > 0) { /* if there is any pending EOBRUN */
319 temp = entropy->EOBRUN;
320 nbits = 0;
321 while ((temp >>= 1))
322 nbits++;
Thomas G. Lane5ead57a1998-03-27 00:00:00 +0000323 /* safety check: shouldn't happen given limited correction-bit buffer */
324 if (nbits > 14)
325 ERREXIT(entropy->cinfo, JERR_HUFF_MISSING_CODE);
Thomas G. Lanebc79e061995-08-02 00:00:00 +0000326
327 emit_symbol(entropy, entropy->ac_tbl_no, nbits << 4);
328 if (nbits)
329 emit_bits(entropy, entropy->EOBRUN, nbits);
330
331 entropy->EOBRUN = 0;
332
333 /* Emit any buffered correction bits */
334 emit_buffered_bits(entropy, entropy->bit_buffer, entropy->BE);
335 entropy->BE = 0;
336 }
337}
338
339
340/*
341 * Emit a restart marker & resynchronize predictions.
342 */
343
Thomas G. Lane489583f1996-02-07 00:00:00 +0000344LOCAL(void)
Thomas G. Lanebc79e061995-08-02 00:00:00 +0000345emit_restart (phuff_entropy_ptr entropy, int restart_num)
346{
347 int ci;
348
349 emit_eobrun(entropy);
350
351 if (! entropy->gather_statistics) {
352 flush_bits(entropy);
353 emit_byte(entropy, 0xFF);
354 emit_byte(entropy, JPEG_RST0 + restart_num);
355 }
356
357 if (entropy->cinfo->Ss == 0) {
358 /* Re-initialize DC predictions to 0 */
359 for (ci = 0; ci < entropy->cinfo->comps_in_scan; ci++)
360 entropy->last_dc_val[ci] = 0;
361 } else {
362 /* Re-initialize all AC-related fields to 0 */
363 entropy->EOBRUN = 0;
364 entropy->BE = 0;
365 }
366}
367
368
369/*
370 * MCU encoding for DC initial scan (either spectral selection,
371 * or first pass of successive approximation).
372 */
373
Thomas G. Lane489583f1996-02-07 00:00:00 +0000374METHODDEF(boolean)
Thomas G. Lanebc79e061995-08-02 00:00:00 +0000375encode_mcu_DC_first (j_compress_ptr cinfo, JBLOCKROW *MCU_data)
376{
377 phuff_entropy_ptr entropy = (phuff_entropy_ptr) cinfo->entropy;
378 register int temp, temp2;
379 register int nbits;
380 int blkn, ci;
381 int Al = cinfo->Al;
382 JBLOCKROW block;
383 jpeg_component_info * compptr;
384 ISHIFT_TEMPS
385
386 entropy->next_output_byte = cinfo->dest->next_output_byte;
387 entropy->free_in_buffer = cinfo->dest->free_in_buffer;
388
389 /* Emit restart marker if needed */
390 if (cinfo->restart_interval)
391 if (entropy->restarts_to_go == 0)
392 emit_restart(entropy, entropy->next_restart_num);
393
394 /* Encode the MCU data blocks */
395 for (blkn = 0; blkn < cinfo->blocks_in_MCU; blkn++) {
396 block = MCU_data[blkn];
397 ci = cinfo->MCU_membership[blkn];
398 compptr = cinfo->cur_comp_info[ci];
399
400 /* Compute the DC value after the required point transform by Al.
401 * This is simply an arithmetic right shift.
402 */
403 temp2 = IRIGHT_SHIFT((int) ((*block)[0]), Al);
404
405 /* DC differences are figured on the point-transformed values. */
406 temp = temp2 - entropy->last_dc_val[ci];
407 entropy->last_dc_val[ci] = temp2;
408
409 /* Encode the DC coefficient difference per section G.1.2.1 */
410 temp2 = temp;
411 if (temp < 0) {
412 temp = -temp; /* temp is abs value of input */
413 /* For a negative input, want temp2 = bitwise complement of abs(input) */
414 /* This code assumes we are on a two's complement machine */
415 temp2--;
416 }
417
418 /* Find the number of bits needed for the magnitude of the coefficient */
419 nbits = 0;
420 while (temp) {
421 nbits++;
422 temp >>= 1;
423 }
Thomas G. Lane5ead57a1998-03-27 00:00:00 +0000424 /* Check for out-of-range coefficient values.
425 * Since we're encoding a difference, the range limit is twice as much.
426 */
427 if (nbits > MAX_COEF_BITS+1)
428 ERREXIT(cinfo, JERR_BAD_DCT_COEF);
Thomas G. Lanebc79e061995-08-02 00:00:00 +0000429
430 /* Count/emit the Huffman-coded symbol for the number of bits */
431 emit_symbol(entropy, compptr->dc_tbl_no, nbits);
432
433 /* Emit that number of bits of the value, if positive, */
434 /* or the complement of its magnitude, if negative. */
435 if (nbits) /* emit_bits rejects calls with size 0 */
436 emit_bits(entropy, (unsigned int) temp2, nbits);
437 }
438
439 cinfo->dest->next_output_byte = entropy->next_output_byte;
440 cinfo->dest->free_in_buffer = entropy->free_in_buffer;
441
442 /* Update restart-interval state too */
443 if (cinfo->restart_interval) {
444 if (entropy->restarts_to_go == 0) {
445 entropy->restarts_to_go = cinfo->restart_interval;
446 entropy->next_restart_num++;
447 entropy->next_restart_num &= 7;
448 }
449 entropy->restarts_to_go--;
450 }
451
452 return TRUE;
453}
454
455
456/*
457 * MCU encoding for AC initial scan (either spectral selection,
458 * or first pass of successive approximation).
459 */
460
Thomas G. Lane489583f1996-02-07 00:00:00 +0000461METHODDEF(boolean)
Thomas G. Lanebc79e061995-08-02 00:00:00 +0000462encode_mcu_AC_first (j_compress_ptr cinfo, JBLOCKROW *MCU_data)
463{
464 phuff_entropy_ptr entropy = (phuff_entropy_ptr) cinfo->entropy;
465 register int temp, temp2;
466 register int nbits;
467 register int r, k;
468 int Se = cinfo->Se;
469 int Al = cinfo->Al;
470 JBLOCKROW block;
471
472 entropy->next_output_byte = cinfo->dest->next_output_byte;
473 entropy->free_in_buffer = cinfo->dest->free_in_buffer;
474
475 /* Emit restart marker if needed */
476 if (cinfo->restart_interval)
477 if (entropy->restarts_to_go == 0)
478 emit_restart(entropy, entropy->next_restart_num);
479
480 /* Encode the MCU data block */
481 block = MCU_data[0];
482
483 /* Encode the AC coefficients per section G.1.2.2, fig. G.3 */
484
485 r = 0; /* r = run length of zeros */
486
487 for (k = cinfo->Ss; k <= Se; k++) {
488 if ((temp = (*block)[jpeg_natural_order[k]]) == 0) {
489 r++;
490 continue;
491 }
492 /* We must apply the point transform by Al. For AC coefficients this
493 * is an integer division with rounding towards 0. To do this portably
494 * in C, we shift after obtaining the absolute value; so the code is
495 * interwoven with finding the abs value (temp) and output bits (temp2).
496 */
497 if (temp < 0) {
498 temp = -temp; /* temp is abs value of input */
499 temp >>= Al; /* apply the point transform */
500 /* For a negative coef, want temp2 = bitwise complement of abs(coef) */
501 temp2 = ~temp;
502 } else {
503 temp >>= Al; /* apply the point transform */
504 temp2 = temp;
505 }
506 /* Watch out for case that nonzero coef is zero after point transform */
507 if (temp == 0) {
508 r++;
509 continue;
510 }
511
512 /* Emit any pending EOBRUN */
513 if (entropy->EOBRUN > 0)
514 emit_eobrun(entropy);
515 /* if run length > 15, must emit special run-length-16 codes (0xF0) */
516 while (r > 15) {
517 emit_symbol(entropy, entropy->ac_tbl_no, 0xF0);
518 r -= 16;
519 }
520
521 /* Find the number of bits needed for the magnitude of the coefficient */
522 nbits = 1; /* there must be at least one 1 bit */
523 while ((temp >>= 1))
524 nbits++;
Thomas G. Lane5ead57a1998-03-27 00:00:00 +0000525 /* Check for out-of-range coefficient values */
526 if (nbits > MAX_COEF_BITS)
527 ERREXIT(cinfo, JERR_BAD_DCT_COEF);
Thomas G. Lanebc79e061995-08-02 00:00:00 +0000528
529 /* Count/emit Huffman symbol for run length / number of bits */
530 emit_symbol(entropy, entropy->ac_tbl_no, (r << 4) + nbits);
531
532 /* Emit that number of bits of the value, if positive, */
533 /* or the complement of its magnitude, if negative. */
534 emit_bits(entropy, (unsigned int) temp2, nbits);
535
536 r = 0; /* reset zero run length */
537 }
538
539 if (r > 0) { /* If there are trailing zeroes, */
540 entropy->EOBRUN++; /* count an EOB */
541 if (entropy->EOBRUN == 0x7FFF)
542 emit_eobrun(entropy); /* force it out to avoid overflow */
543 }
544
545 cinfo->dest->next_output_byte = entropy->next_output_byte;
546 cinfo->dest->free_in_buffer = entropy->free_in_buffer;
547
548 /* Update restart-interval state too */
549 if (cinfo->restart_interval) {
550 if (entropy->restarts_to_go == 0) {
551 entropy->restarts_to_go = cinfo->restart_interval;
552 entropy->next_restart_num++;
553 entropy->next_restart_num &= 7;
554 }
555 entropy->restarts_to_go--;
556 }
557
558 return TRUE;
559}
560
561
562/*
563 * MCU encoding for DC successive approximation refinement scan.
564 * Note: we assume such scans can be multi-component, although the spec
565 * is not very clear on the point.
566 */
567
Thomas G. Lane489583f1996-02-07 00:00:00 +0000568METHODDEF(boolean)
Thomas G. Lanebc79e061995-08-02 00:00:00 +0000569encode_mcu_DC_refine (j_compress_ptr cinfo, JBLOCKROW *MCU_data)
570{
571 phuff_entropy_ptr entropy = (phuff_entropy_ptr) cinfo->entropy;
572 register int temp;
573 int blkn;
574 int Al = cinfo->Al;
575 JBLOCKROW block;
576
577 entropy->next_output_byte = cinfo->dest->next_output_byte;
578 entropy->free_in_buffer = cinfo->dest->free_in_buffer;
579
580 /* Emit restart marker if needed */
581 if (cinfo->restart_interval)
582 if (entropy->restarts_to_go == 0)
583 emit_restart(entropy, entropy->next_restart_num);
584
585 /* Encode the MCU data blocks */
586 for (blkn = 0; blkn < cinfo->blocks_in_MCU; blkn++) {
587 block = MCU_data[blkn];
588
589 /* We simply emit the Al'th bit of the DC coefficient value. */
590 temp = (*block)[0];
591 emit_bits(entropy, (unsigned int) (temp >> Al), 1);
592 }
593
594 cinfo->dest->next_output_byte = entropy->next_output_byte;
595 cinfo->dest->free_in_buffer = entropy->free_in_buffer;
596
597 /* Update restart-interval state too */
598 if (cinfo->restart_interval) {
599 if (entropy->restarts_to_go == 0) {
600 entropy->restarts_to_go = cinfo->restart_interval;
601 entropy->next_restart_num++;
602 entropy->next_restart_num &= 7;
603 }
604 entropy->restarts_to_go--;
605 }
606
607 return TRUE;
608}
609
610
611/*
612 * MCU encoding for AC successive approximation refinement scan.
613 */
614
Thomas G. Lane489583f1996-02-07 00:00:00 +0000615METHODDEF(boolean)
Thomas G. Lanebc79e061995-08-02 00:00:00 +0000616encode_mcu_AC_refine (j_compress_ptr cinfo, JBLOCKROW *MCU_data)
617{
618 phuff_entropy_ptr entropy = (phuff_entropy_ptr) cinfo->entropy;
619 register int temp;
620 register int r, k;
621 int EOB;
622 char *BR_buffer;
623 unsigned int BR;
624 int Se = cinfo->Se;
625 int Al = cinfo->Al;
626 JBLOCKROW block;
627 int absvalues[DCTSIZE2];
628
629 entropy->next_output_byte = cinfo->dest->next_output_byte;
630 entropy->free_in_buffer = cinfo->dest->free_in_buffer;
631
632 /* Emit restart marker if needed */
633 if (cinfo->restart_interval)
634 if (entropy->restarts_to_go == 0)
635 emit_restart(entropy, entropy->next_restart_num);
636
637 /* Encode the MCU data block */
638 block = MCU_data[0];
639
640 /* It is convenient to make a pre-pass to determine the transformed
641 * coefficients' absolute values and the EOB position.
642 */
643 EOB = 0;
644 for (k = cinfo->Ss; k <= Se; k++) {
645 temp = (*block)[jpeg_natural_order[k]];
646 /* We must apply the point transform by Al. For AC coefficients this
647 * is an integer division with rounding towards 0. To do this portably
648 * in C, we shift after obtaining the absolute value.
649 */
650 if (temp < 0)
651 temp = -temp; /* temp is abs value of input */
652 temp >>= Al; /* apply the point transform */
653 absvalues[k] = temp; /* save abs value for main pass */
654 if (temp == 1)
655 EOB = k; /* EOB = index of last newly-nonzero coef */
656 }
657
658 /* Encode the AC coefficients per section G.1.2.3, fig. G.7 */
659
660 r = 0; /* r = run length of zeros */
661 BR = 0; /* BR = count of buffered bits added now */
662 BR_buffer = entropy->bit_buffer + entropy->BE; /* Append bits to buffer */
663
664 for (k = cinfo->Ss; k <= Se; k++) {
665 if ((temp = absvalues[k]) == 0) {
666 r++;
667 continue;
668 }
669
670 /* Emit any required ZRLs, but not if they can be folded into EOB */
671 while (r > 15 && k <= EOB) {
672 /* emit any pending EOBRUN and the BE correction bits */
673 emit_eobrun(entropy);
674 /* Emit ZRL */
675 emit_symbol(entropy, entropy->ac_tbl_no, 0xF0);
676 r -= 16;
677 /* Emit buffered correction bits that must be associated with ZRL */
678 emit_buffered_bits(entropy, BR_buffer, BR);
679 BR_buffer = entropy->bit_buffer; /* BE bits are gone now */
680 BR = 0;
681 }
682
683 /* If the coef was previously nonzero, it only needs a correction bit.
684 * NOTE: a straight translation of the spec's figure G.7 would suggest
685 * that we also need to test r > 15. But if r > 15, we can only get here
686 * if k > EOB, which implies that this coefficient is not 1.
687 */
688 if (temp > 1) {
689 /* The correction bit is the next bit of the absolute value. */
690 BR_buffer[BR++] = (char) (temp & 1);
691 continue;
692 }
693
694 /* Emit any pending EOBRUN and the BE correction bits */
695 emit_eobrun(entropy);
696
697 /* Count/emit Huffman symbol for run length / number of bits */
698 emit_symbol(entropy, entropy->ac_tbl_no, (r << 4) + 1);
699
700 /* Emit output bit for newly-nonzero coef */
701 temp = ((*block)[jpeg_natural_order[k]] < 0) ? 0 : 1;
702 emit_bits(entropy, (unsigned int) temp, 1);
703
704 /* Emit buffered correction bits that must be associated with this code */
705 emit_buffered_bits(entropy, BR_buffer, BR);
706 BR_buffer = entropy->bit_buffer; /* BE bits are gone now */
707 BR = 0;
708 r = 0; /* reset zero run length */
709 }
710
711 if (r > 0 || BR > 0) { /* If there are trailing zeroes, */
712 entropy->EOBRUN++; /* count an EOB */
713 entropy->BE += BR; /* concat my correction bits to older ones */
714 /* We force out the EOB if we risk either:
715 * 1. overflow of the EOB counter;
716 * 2. overflow of the correction bit buffer during the next MCU.
717 */
718 if (entropy->EOBRUN == 0x7FFF || entropy->BE > (MAX_CORR_BITS-DCTSIZE2+1))
719 emit_eobrun(entropy);
720 }
721
722 cinfo->dest->next_output_byte = entropy->next_output_byte;
723 cinfo->dest->free_in_buffer = entropy->free_in_buffer;
724
725 /* Update restart-interval state too */
726 if (cinfo->restart_interval) {
727 if (entropy->restarts_to_go == 0) {
728 entropy->restarts_to_go = cinfo->restart_interval;
729 entropy->next_restart_num++;
730 entropy->next_restart_num &= 7;
731 }
732 entropy->restarts_to_go--;
733 }
734
735 return TRUE;
736}
737
738
739/*
740 * Finish up at the end of a Huffman-compressed progressive scan.
741 */
742
Thomas G. Lane489583f1996-02-07 00:00:00 +0000743METHODDEF(void)
Thomas G. Lanebc79e061995-08-02 00:00:00 +0000744finish_pass_phuff (j_compress_ptr cinfo)
745{
746 phuff_entropy_ptr entropy = (phuff_entropy_ptr) cinfo->entropy;
747
748 entropy->next_output_byte = cinfo->dest->next_output_byte;
749 entropy->free_in_buffer = cinfo->dest->free_in_buffer;
750
751 /* Flush out any buffered data */
752 emit_eobrun(entropy);
753 flush_bits(entropy);
754
755 cinfo->dest->next_output_byte = entropy->next_output_byte;
756 cinfo->dest->free_in_buffer = entropy->free_in_buffer;
757}
758
759
760/*
761 * Finish up a statistics-gathering pass and create the new Huffman tables.
762 */
763
Thomas G. Lane489583f1996-02-07 00:00:00 +0000764METHODDEF(void)
Thomas G. Lanebc79e061995-08-02 00:00:00 +0000765finish_pass_gather_phuff (j_compress_ptr cinfo)
766{
767 phuff_entropy_ptr entropy = (phuff_entropy_ptr) cinfo->entropy;
768 boolean is_DC_band;
769 int ci, tbl;
770 jpeg_component_info * compptr;
771 JHUFF_TBL **htblptr;
772 boolean did[NUM_HUFF_TBLS];
773
774 /* Flush out buffered data (all we care about is counting the EOB symbol) */
775 emit_eobrun(entropy);
776
777 is_DC_band = (cinfo->Ss == 0);
778
779 /* It's important not to apply jpeg_gen_optimal_table more than once
780 * per table, because it clobbers the input frequency counts!
781 */
782 MEMZERO(did, SIZEOF(did));
783
784 for (ci = 0; ci < cinfo->comps_in_scan; ci++) {
785 compptr = cinfo->cur_comp_info[ci];
786 if (is_DC_band) {
787 if (cinfo->Ah != 0) /* DC refinement needs no table */
788 continue;
789 tbl = compptr->dc_tbl_no;
790 } else {
791 tbl = compptr->ac_tbl_no;
792 }
793 if (! did[tbl]) {
794 if (is_DC_band)
795 htblptr = & cinfo->dc_huff_tbl_ptrs[tbl];
796 else
797 htblptr = & cinfo->ac_huff_tbl_ptrs[tbl];
798 if (*htblptr == NULL)
799 *htblptr = jpeg_alloc_huff_table((j_common_ptr) cinfo);
800 jpeg_gen_optimal_table(cinfo, *htblptr, entropy->count_ptrs[tbl]);
801 did[tbl] = TRUE;
802 }
803 }
804}
805
806
807/*
808 * Module initialization routine for progressive Huffman entropy encoding.
809 */
810
Thomas G. Lane489583f1996-02-07 00:00:00 +0000811GLOBAL(void)
Thomas G. Lanebc79e061995-08-02 00:00:00 +0000812jinit_phuff_encoder (j_compress_ptr cinfo)
813{
814 phuff_entropy_ptr entropy;
815 int i;
816
817 entropy = (phuff_entropy_ptr)
818 (*cinfo->mem->alloc_small) ((j_common_ptr) cinfo, JPOOL_IMAGE,
819 SIZEOF(phuff_entropy_encoder));
820 cinfo->entropy = (struct jpeg_entropy_encoder *) entropy;
821 entropy->pub.start_pass = start_pass_phuff;
822
823 /* Mark tables unallocated */
824 for (i = 0; i < NUM_HUFF_TBLS; i++) {
825 entropy->derived_tbls[i] = NULL;
826 entropy->count_ptrs[i] = NULL;
827 }
828 entropy->bit_buffer = NULL; /* needed only in AC refinement scan */
829}
830
831#endif /* C_PROGRESSIVE_SUPPORTED */