4
* Copyright (C) 1991-1997, Thomas G. Lane.
5
* Modified 2006-2009 by Guido Vollbeding.
6
* This file is part of the Independent JPEG Group's software.
7
* For conditions of distribution and use, see the accompanying README file.
9
* This file contains Huffman entropy encoding routines.
10
* Both sequential and progressive modes are supported in this single module.
12
* Much of the complexity here has to do with supporting output suspension.
13
* If the data destination module demands suspension, we want to be able to
14
* back up to the start of the current MCU. To do this, we copy state
15
* variables into local working storage, and update them back to the
16
* permanent JPEG objects only upon successful completion of an MCU.
18
* We do not support output suspension for the progressive JPEG mode, since
19
* the library currently does not allow multiple-scan files to be written
20
* with output suspension.
23
#define JPEG_INTERNALS
28
/* The legal range of a DCT coefficient is
29
* -1024 .. +1023 for 8-bit data;
30
* -16384 .. +16383 for 12-bit data.
31
* Hence the magnitude should always fit in 10 or 14 bits respectively.
34
#if BITS_IN_JSAMPLE == 8
35
#define MAX_COEF_BITS 10
37
#define MAX_COEF_BITS 14
40
/* Derived data constructed for each Huffman table */
43
unsigned int ehufco[256]; /* code for each symbol */
44
char ehufsi[256]; /* length of code for each symbol */
45
/* If no code has been allocated for a symbol S, ehufsi[S] contains 0 */
49
/* Expanded entropy encoder object for Huffman encoding.
51
* The savable_state subrecord contains fields that change within an MCU,
52
* but must not be updated permanently until we complete the MCU.
56
INT32 put_buffer; /* current bit-accumulation buffer */
57
int put_bits; /* # of bits now in it */
58
int last_dc_val[MAX_COMPS_IN_SCAN]; /* last DC coef for each component */
61
/* This macro is to work around compilers with missing or broken
62
* structure assignment. You'll need to fix this code if you have
63
* such a compiler and you change MAX_COMPS_IN_SCAN.
66
#ifndef NO_STRUCT_ASSIGN
67
#define ASSIGN_STATE(dest,src) ((dest) = (src))
69
#if MAX_COMPS_IN_SCAN == 4
70
#define ASSIGN_STATE(dest,src) \
71
((dest).put_buffer = (src).put_buffer, \
72
(dest).put_bits = (src).put_bits, \
73
(dest).last_dc_val[0] = (src).last_dc_val[0], \
74
(dest).last_dc_val[1] = (src).last_dc_val[1], \
75
(dest).last_dc_val[2] = (src).last_dc_val[2], \
76
(dest).last_dc_val[3] = (src).last_dc_val[3])
82
struct jpeg_entropy_encoder pub; /* public fields */
84
savable_state saved; /* Bit buffer & DC state at start of MCU */
86
/* These fields are NOT loaded into local working state. */
87
unsigned int restarts_to_go; /* MCUs left in this restart interval */
88
int next_restart_num; /* next restart number to write (0-7) */
90
/* Pointers to derived tables (these workspaces have image lifespan) */
91
c_derived_tbl * dc_derived_tbls[NUM_HUFF_TBLS];
92
c_derived_tbl * ac_derived_tbls[NUM_HUFF_TBLS];
94
/* Statistics tables for optimization */
95
long * dc_count_ptrs[NUM_HUFF_TBLS];
96
long * ac_count_ptrs[NUM_HUFF_TBLS];
98
/* Following fields used only in progressive mode */
100
/* Mode flag: TRUE for optimization, FALSE for actual data output */
101
boolean gather_statistics;
103
/* next_output_byte/free_in_buffer are local copies of cinfo->dest fields.
105
JOCTET * next_output_byte; /* => next byte to write in buffer */
106
size_t free_in_buffer; /* # of byte spaces remaining in buffer */
107
j_compress_ptr cinfo; /* link to cinfo (needed for dump_buffer) */
109
/* Coding status for AC components */
110
int ac_tbl_no; /* the table number of the single component */
111
unsigned int EOBRUN; /* run length of EOBs */
112
unsigned int BE; /* # of buffered correction bits before MCU */
113
char * bit_buffer; /* buffer for correction bits (1 per char) */
114
/* packing correction bits tightly would save some space but cost time... */
115
} huff_entropy_encoder;
117
typedef huff_entropy_encoder * huff_entropy_ptr;
119
/* Working state while writing an MCU (sequential mode).
120
* This struct contains all the fields that are needed by subroutines.
124
JOCTET * next_output_byte; /* => next byte to write in buffer */
125
size_t free_in_buffer; /* # of byte spaces remaining in buffer */
126
savable_state cur; /* Current bit buffer & DC state */
127
j_compress_ptr cinfo; /* dump_buffer needs access to this */
130
/* MAX_CORR_BITS is the number of bits the AC refinement correction-bit
131
* buffer can hold. Larger sizes may slightly improve compression, but
132
* 1000 is already well into the realm of overkill.
133
* The minimum safe size is 64 bits.
136
#define MAX_CORR_BITS 1000 /* Max # of correction bits I can buffer */
138
/* IRIGHT_SHIFT is like RIGHT_SHIFT, but works on int rather than INT32.
139
* We assume that int right shift is unsigned if INT32 right shift is,
140
* which should be safe.
143
#ifdef RIGHT_SHIFT_IS_UNSIGNED
144
#define ISHIFT_TEMPS int ishift_temp;
145
#define IRIGHT_SHIFT(x,shft) \
146
((ishift_temp = (x)) < 0 ? \
147
(ishift_temp >> (shft)) | ((~0) << (16-(shft))) : \
148
(ishift_temp >> (shft)))
151
#define IRIGHT_SHIFT(x,shft) ((x) >> (shft))
156
* Compute the derived values for a Huffman table.
157
* This routine also performs some validation checks on the table.
161
jpeg_make_c_derived_tbl (j_compress_ptr cinfo, boolean isDC, int tblno,
162
c_derived_tbl ** pdtbl)
166
int p, i, l, lastp, si, maxsymbol;
168
unsigned int huffcode[257];
171
/* Note that huffsize[] and huffcode[] are filled in code-length order,
172
* paralleling the order of the symbols themselves in htbl->huffval[].
175
/* Find the input Huffman table */
176
if (tblno < 0 || tblno >= NUM_HUFF_TBLS)
177
ERREXIT1(cinfo, JERR_NO_HUFF_TABLE, tblno);
179
isDC ? cinfo->dc_huff_tbl_ptrs[tblno] : cinfo->ac_huff_tbl_ptrs[tblno];
181
ERREXIT1(cinfo, JERR_NO_HUFF_TABLE, tblno);
183
/* Allocate a workspace if we haven't already done so. */
185
*pdtbl = (c_derived_tbl *)
186
(*cinfo->mem->alloc_small) ((j_common_ptr) cinfo, JPOOL_IMAGE,
187
SIZEOF(c_derived_tbl));
190
/* Figure C.1: make table of Huffman code length for each symbol */
193
for (l = 1; l <= 16; l++) {
194
i = (int) htbl->bits[l];
195
if (i < 0 || p + i > 256) /* protect against table overrun */
196
ERREXIT(cinfo, JERR_BAD_HUFF_TABLE);
198
huffsize[p++] = (char) l;
203
/* Figure C.2: generate the codes themselves */
204
/* We also validate that the counts represent a legal Huffman code tree. */
209
while (huffsize[p]) {
210
while (((int) huffsize[p]) == si) {
211
huffcode[p++] = code;
214
/* code is now 1 more than the last code used for codelength si; but
215
* it must still fit in si bits, since no code is allowed to be all ones.
217
if (((INT32) code) >= (((INT32) 1) << si))
218
ERREXIT(cinfo, JERR_BAD_HUFF_TABLE);
223
/* Figure C.3: generate encoding tables */
224
/* These are code and size indexed by symbol value */
226
/* Set all codeless symbols to have code length 0;
227
* this lets us detect duplicate VAL entries here, and later
228
* allows emit_bits to detect any attempt to emit such symbols.
230
MEMZERO(dtbl->ehufsi, SIZEOF(dtbl->ehufsi));
232
/* This is also a convenient place to check for out-of-range
233
* and duplicated VAL entries. We allow 0..255 for AC symbols
234
* but only 0..15 for DC. (We could constrain them further
235
* based on data depth and mode, but this seems enough.)
237
maxsymbol = isDC ? 15 : 255;
239
for (p = 0; p < lastp; p++) {
240
i = htbl->huffval[p];
241
if (i < 0 || i > maxsymbol || dtbl->ehufsi[i])
242
ERREXIT(cinfo, JERR_BAD_HUFF_TABLE);
243
dtbl->ehufco[i] = huffcode[p];
244
dtbl->ehufsi[i] = huffsize[p];
249
/* Outputting bytes to the file.
250
* NB: these must be called only when actually outputting,
251
* that is, entropy->gather_statistics == FALSE.
254
/* Emit a byte, taking 'action' if must suspend. */
255
#define emit_byte_s(state,val,action) \
256
{ *(state)->next_output_byte++ = (JOCTET) (val); \
257
if (--(state)->free_in_buffer == 0) \
258
if (! dump_buffer_s(state)) \
262
#define emit_byte_e(entropy,val) \
263
{ *(entropy)->next_output_byte++ = (JOCTET) (val); \
264
if (--(entropy)->free_in_buffer == 0) \
265
dump_buffer_e(entropy); }
269
dump_buffer_s (working_state * state)
270
/* Empty the output buffer; return TRUE if successful, FALSE if must suspend */
272
struct jpeg_destination_mgr * dest = state->cinfo->dest;
274
if (! (*dest->empty_output_buffer) (state->cinfo))
276
/* After a successful buffer dump, must reset buffer pointers */
277
state->next_output_byte = dest->next_output_byte;
278
state->free_in_buffer = dest->free_in_buffer;
284
dump_buffer_e (huff_entropy_ptr entropy)
285
/* Empty the output buffer; we do not support suspension in this case. */
287
struct jpeg_destination_mgr * dest = entropy->cinfo->dest;
289
if (! (*dest->empty_output_buffer) (entropy->cinfo))
290
ERREXIT(entropy->cinfo, JERR_CANT_SUSPEND);
291
/* After a successful buffer dump, must reset buffer pointers */
292
entropy->next_output_byte = dest->next_output_byte;
293
entropy->free_in_buffer = dest->free_in_buffer;
297
/* Outputting bits to the file */
299
/* Only the right 24 bits of put_buffer are used; the valid bits are
300
* left-justified in this part. At most 16 bits can be passed to emit_bits
301
* in one call, and we never retain more than 7 bits in put_buffer
302
* between calls, so 24 bits are sufficient.
307
emit_bits_s (working_state * state, unsigned int code, int size)
308
/* Emit some bits; return TRUE if successful, FALSE if must suspend */
310
/* This routine is heavily used, so it's worth coding tightly. */
311
register INT32 put_buffer = (INT32) code;
312
register int put_bits = state->cur.put_bits;
314
/* if size is 0, caller used an invalid Huffman table entry */
316
ERREXIT(state->cinfo, JERR_HUFF_MISSING_CODE);
318
put_buffer &= (((INT32) 1)<<size) - 1; /* mask off any extra bits in code */
320
put_bits += size; /* new number of bits in buffer */
322
put_buffer <<= 24 - put_bits; /* align incoming bits */
324
put_buffer |= state->cur.put_buffer; /* and merge with old buffer contents */
326
while (put_bits >= 8) {
327
int c = (int) ((put_buffer >> 16) & 0xFF);
329
emit_byte_s(state, c, return FALSE);
330
if (c == 0xFF) { /* need to stuff a zero byte? */
331
emit_byte_s(state, 0, return FALSE);
337
state->cur.put_buffer = put_buffer; /* update state variables */
338
state->cur.put_bits = put_bits;
346
emit_bits_e (huff_entropy_ptr entropy, unsigned int code, int size)
347
/* Emit some bits, unless we are in gather mode */
349
/* This routine is heavily used, so it's worth coding tightly. */
350
register INT32 put_buffer = (INT32) code;
351
register int put_bits = entropy->saved.put_bits;
353
/* if size is 0, caller used an invalid Huffman table entry */
355
ERREXIT(entropy->cinfo, JERR_HUFF_MISSING_CODE);
357
if (entropy->gather_statistics)
358
return; /* do nothing if we're only getting stats */
360
put_buffer &= (((INT32) 1)<<size) - 1; /* mask off any extra bits in code */
362
put_bits += size; /* new number of bits in buffer */
364
put_buffer <<= 24 - put_bits; /* align incoming bits */
366
/* and merge with old buffer contents */
367
put_buffer |= entropy->saved.put_buffer;
369
while (put_bits >= 8) {
370
int c = (int) ((put_buffer >> 16) & 0xFF);
372
emit_byte_e(entropy, c);
373
if (c == 0xFF) { /* need to stuff a zero byte? */
374
emit_byte_e(entropy, 0);
380
entropy->saved.put_buffer = put_buffer; /* update variables */
381
entropy->saved.put_bits = put_bits;
386
flush_bits_s (working_state * state)
388
if (! emit_bits_s(state, 0x7F, 7)) /* fill any partial byte with ones */
390
state->cur.put_buffer = 0; /* and reset bit-buffer to empty */
391
state->cur.put_bits = 0;
397
flush_bits_e (huff_entropy_ptr entropy)
399
emit_bits_e(entropy, 0x7F, 7); /* fill any partial byte with ones */
400
entropy->saved.put_buffer = 0; /* and reset bit-buffer to empty */
401
entropy->saved.put_bits = 0;
406
* Emit (or just count) a Huffman symbol.
411
emit_dc_symbol (huff_entropy_ptr entropy, int tbl_no, int symbol)
413
if (entropy->gather_statistics)
414
entropy->dc_count_ptrs[tbl_no][symbol]++;
416
c_derived_tbl * tbl = entropy->dc_derived_tbls[tbl_no];
417
emit_bits_e(entropy, tbl->ehufco[symbol], tbl->ehufsi[symbol]);
424
emit_ac_symbol (huff_entropy_ptr entropy, int tbl_no, int symbol)
426
if (entropy->gather_statistics)
427
entropy->ac_count_ptrs[tbl_no][symbol]++;
429
c_derived_tbl * tbl = entropy->ac_derived_tbls[tbl_no];
430
emit_bits_e(entropy, tbl->ehufco[symbol], tbl->ehufsi[symbol]);
436
* Emit bits from a correction bit buffer.
440
emit_buffered_bits (huff_entropy_ptr entropy, char * bufstart,
443
if (entropy->gather_statistics)
444
return; /* no real work */
447
emit_bits_e(entropy, (unsigned int) (*bufstart), 1);
455
* Emit any pending EOBRUN symbol.
459
emit_eobrun (huff_entropy_ptr entropy)
461
register int temp, nbits;
463
if (entropy->EOBRUN > 0) { /* if there is any pending EOBRUN */
464
temp = entropy->EOBRUN;
468
/* safety check: shouldn't happen given limited correction-bit buffer */
470
ERREXIT(entropy->cinfo, JERR_HUFF_MISSING_CODE);
472
emit_ac_symbol(entropy, entropy->ac_tbl_no, nbits << 4);
474
emit_bits_e(entropy, entropy->EOBRUN, nbits);
478
/* Emit any buffered correction bits */
479
emit_buffered_bits(entropy, entropy->bit_buffer, entropy->BE);
486
* Emit a restart marker & resynchronize predictions.
490
emit_restart_s (working_state * state, int restart_num)
494
if (! flush_bits_s(state))
497
emit_byte_s(state, 0xFF, return FALSE);
498
emit_byte_s(state, JPEG_RST0 + restart_num, return FALSE);
500
/* Re-initialize DC predictions to 0 */
501
for (ci = 0; ci < state->cinfo->comps_in_scan; ci++)
502
state->cur.last_dc_val[ci] = 0;
504
/* The restart counter is not updated until we successfully write the MCU. */
511
emit_restart_e (huff_entropy_ptr entropy, int restart_num)
515
emit_eobrun(entropy);
517
if (! entropy->gather_statistics) {
518
flush_bits_e(entropy);
519
emit_byte_e(entropy, 0xFF);
520
emit_byte_e(entropy, JPEG_RST0 + restart_num);
523
if (entropy->cinfo->Ss == 0) {
524
/* Re-initialize DC predictions to 0 */
525
for (ci = 0; ci < entropy->cinfo->comps_in_scan; ci++)
526
entropy->saved.last_dc_val[ci] = 0;
528
/* Re-initialize all AC-related fields to 0 */
536
* MCU encoding for DC initial scan (either spectral selection,
537
* or first pass of successive approximation).
541
encode_mcu_DC_first (j_compress_ptr cinfo, JBLOCKROW *MCU_data)
543
huff_entropy_ptr entropy = (huff_entropy_ptr) cinfo->entropy;
544
register int temp, temp2;
549
jpeg_component_info * compptr;
552
entropy->next_output_byte = cinfo->dest->next_output_byte;
553
entropy->free_in_buffer = cinfo->dest->free_in_buffer;
555
/* Emit restart marker if needed */
556
if (cinfo->restart_interval)
557
if (entropy->restarts_to_go == 0)
558
emit_restart_e(entropy, entropy->next_restart_num);
560
/* Encode the MCU data blocks */
561
for (blkn = 0; blkn < cinfo->blocks_in_MCU; blkn++) {
562
block = MCU_data[blkn];
563
ci = cinfo->MCU_membership[blkn];
564
compptr = cinfo->cur_comp_info[ci];
566
/* Compute the DC value after the required point transform by Al.
567
* This is simply an arithmetic right shift.
569
temp2 = IRIGHT_SHIFT((int) ((*block)[0]), Al);
571
/* DC differences are figured on the point-transformed values. */
572
temp = temp2 - entropy->saved.last_dc_val[ci];
573
entropy->saved.last_dc_val[ci] = temp2;
575
/* Encode the DC coefficient difference per section G.1.2.1 */
578
temp = -temp; /* temp is abs value of input */
579
/* For a negative input, want temp2 = bitwise complement of abs(input) */
580
/* This code assumes we are on a two's complement machine */
584
/* Find the number of bits needed for the magnitude of the coefficient */
590
/* Check for out-of-range coefficient values.
591
* Since we're encoding a difference, the range limit is twice as much.
593
if (nbits > MAX_COEF_BITS+1)
594
ERREXIT(cinfo, JERR_BAD_DCT_COEF);
596
/* Count/emit the Huffman-coded symbol for the number of bits */
597
emit_dc_symbol(entropy, compptr->dc_tbl_no, nbits);
599
/* Emit that number of bits of the value, if positive, */
600
/* or the complement of its magnitude, if negative. */
601
if (nbits) /* emit_bits rejects calls with size 0 */
602
emit_bits_e(entropy, (unsigned int) temp2, nbits);
605
cinfo->dest->next_output_byte = entropy->next_output_byte;
606
cinfo->dest->free_in_buffer = entropy->free_in_buffer;
608
/* Update restart-interval state too */
609
if (cinfo->restart_interval) {
610
if (entropy->restarts_to_go == 0) {
611
entropy->restarts_to_go = cinfo->restart_interval;
612
entropy->next_restart_num++;
613
entropy->next_restart_num &= 7;
615
entropy->restarts_to_go--;
623
* MCU encoding for AC initial scan (either spectral selection,
624
* or first pass of successive approximation).
628
encode_mcu_AC_first (j_compress_ptr cinfo, JBLOCKROW *MCU_data)
630
huff_entropy_ptr entropy = (huff_entropy_ptr) cinfo->entropy;
631
register int temp, temp2;
635
const int * natural_order;
638
entropy->next_output_byte = cinfo->dest->next_output_byte;
639
entropy->free_in_buffer = cinfo->dest->free_in_buffer;
641
/* Emit restart marker if needed */
642
if (cinfo->restart_interval)
643
if (entropy->restarts_to_go == 0)
644
emit_restart_e(entropy, entropy->next_restart_num);
648
natural_order = cinfo->natural_order;
650
/* Encode the MCU data block */
653
/* Encode the AC coefficients per section G.1.2.2, fig. G.3 */
655
r = 0; /* r = run length of zeros */
657
for (k = cinfo->Ss; k <= Se; k++) {
658
if ((temp = (*block)[natural_order[k]]) == 0) {
662
/* We must apply the point transform by Al. For AC coefficients this
663
* is an integer division with rounding towards 0. To do this portably
664
* in C, we shift after obtaining the absolute value; so the code is
665
* interwoven with finding the abs value (temp) and output bits (temp2).
668
temp = -temp; /* temp is abs value of input */
669
temp >>= Al; /* apply the point transform */
670
/* For a negative coef, want temp2 = bitwise complement of abs(coef) */
673
temp >>= Al; /* apply the point transform */
676
/* Watch out for case that nonzero coef is zero after point transform */
682
/* Emit any pending EOBRUN */
683
if (entropy->EOBRUN > 0)
684
emit_eobrun(entropy);
685
/* if run length > 15, must emit special run-length-16 codes (0xF0) */
687
emit_ac_symbol(entropy, entropy->ac_tbl_no, 0xF0);
691
/* Find the number of bits needed for the magnitude of the coefficient */
692
nbits = 1; /* there must be at least one 1 bit */
695
/* Check for out-of-range coefficient values */
696
if (nbits > MAX_COEF_BITS)
697
ERREXIT(cinfo, JERR_BAD_DCT_COEF);
699
/* Count/emit Huffman symbol for run length / number of bits */
700
emit_ac_symbol(entropy, entropy->ac_tbl_no, (r << 4) + nbits);
702
/* Emit that number of bits of the value, if positive, */
703
/* or the complement of its magnitude, if negative. */
704
emit_bits_e(entropy, (unsigned int) temp2, nbits);
706
r = 0; /* reset zero run length */
709
if (r > 0) { /* If there are trailing zeroes, */
710
entropy->EOBRUN++; /* count an EOB */
711
if (entropy->EOBRUN == 0x7FFF)
712
emit_eobrun(entropy); /* force it out to avoid overflow */
715
cinfo->dest->next_output_byte = entropy->next_output_byte;
716
cinfo->dest->free_in_buffer = entropy->free_in_buffer;
718
/* Update restart-interval state too */
719
if (cinfo->restart_interval) {
720
if (entropy->restarts_to_go == 0) {
721
entropy->restarts_to_go = cinfo->restart_interval;
722
entropy->next_restart_num++;
723
entropy->next_restart_num &= 7;
725
entropy->restarts_to_go--;
733
* MCU encoding for DC successive approximation refinement scan.
734
* Note: we assume such scans can be multi-component, although the spec
735
* is not very clear on the point.
739
encode_mcu_DC_refine (j_compress_ptr cinfo, JBLOCKROW *MCU_data)
741
huff_entropy_ptr entropy = (huff_entropy_ptr) cinfo->entropy;
747
entropy->next_output_byte = cinfo->dest->next_output_byte;
748
entropy->free_in_buffer = cinfo->dest->free_in_buffer;
750
/* Emit restart marker if needed */
751
if (cinfo->restart_interval)
752
if (entropy->restarts_to_go == 0)
753
emit_restart_e(entropy, entropy->next_restart_num);
755
/* Encode the MCU data blocks */
756
for (blkn = 0; blkn < cinfo->blocks_in_MCU; blkn++) {
757
block = MCU_data[blkn];
759
/* We simply emit the Al'th bit of the DC coefficient value. */
761
emit_bits_e(entropy, (unsigned int) (temp >> Al), 1);
764
cinfo->dest->next_output_byte = entropy->next_output_byte;
765
cinfo->dest->free_in_buffer = entropy->free_in_buffer;
767
/* Update restart-interval state too */
768
if (cinfo->restart_interval) {
769
if (entropy->restarts_to_go == 0) {
770
entropy->restarts_to_go = cinfo->restart_interval;
771
entropy->next_restart_num++;
772
entropy->next_restart_num &= 7;
774
entropy->restarts_to_go--;
782
* MCU encoding for AC successive approximation refinement scan.
786
encode_mcu_AC_refine (j_compress_ptr cinfo, JBLOCKROW *MCU_data)
788
huff_entropy_ptr entropy = (huff_entropy_ptr) cinfo->entropy;
795
const int * natural_order;
797
int absvalues[DCTSIZE2];
799
entropy->next_output_byte = cinfo->dest->next_output_byte;
800
entropy->free_in_buffer = cinfo->dest->free_in_buffer;
802
/* Emit restart marker if needed */
803
if (cinfo->restart_interval)
804
if (entropy->restarts_to_go == 0)
805
emit_restart_e(entropy, entropy->next_restart_num);
809
natural_order = cinfo->natural_order;
811
/* Encode the MCU data block */
814
/* It is convenient to make a pre-pass to determine the transformed
815
* coefficients' absolute values and the EOB position.
818
for (k = cinfo->Ss; k <= Se; k++) {
819
temp = (*block)[natural_order[k]];
820
/* We must apply the point transform by Al. For AC coefficients this
821
* is an integer division with rounding towards 0. To do this portably
822
* in C, we shift after obtaining the absolute value.
825
temp = -temp; /* temp is abs value of input */
826
temp >>= Al; /* apply the point transform */
827
absvalues[k] = temp; /* save abs value for main pass */
829
EOB = k; /* EOB = index of last newly-nonzero coef */
832
/* Encode the AC coefficients per section G.1.2.3, fig. G.7 */
834
r = 0; /* r = run length of zeros */
835
BR = 0; /* BR = count of buffered bits added now */
836
BR_buffer = entropy->bit_buffer + entropy->BE; /* Append bits to buffer */
838
for (k = cinfo->Ss; k <= Se; k++) {
839
if ((temp = absvalues[k]) == 0) {
844
/* Emit any required ZRLs, but not if they can be folded into EOB */
845
while (r > 15 && k <= EOB) {
846
/* emit any pending EOBRUN and the BE correction bits */
847
emit_eobrun(entropy);
849
emit_ac_symbol(entropy, entropy->ac_tbl_no, 0xF0);
851
/* Emit buffered correction bits that must be associated with ZRL */
852
emit_buffered_bits(entropy, BR_buffer, BR);
853
BR_buffer = entropy->bit_buffer; /* BE bits are gone now */
857
/* If the coef was previously nonzero, it only needs a correction bit.
858
* NOTE: a straight translation of the spec's figure G.7 would suggest
859
* that we also need to test r > 15. But if r > 15, we can only get here
860
* if k > EOB, which implies that this coefficient is not 1.
863
/* The correction bit is the next bit of the absolute value. */
864
BR_buffer[BR++] = (char) (temp & 1);
868
/* Emit any pending EOBRUN and the BE correction bits */
869
emit_eobrun(entropy);
871
/* Count/emit Huffman symbol for run length / number of bits */
872
emit_ac_symbol(entropy, entropy->ac_tbl_no, (r << 4) + 1);
874
/* Emit output bit for newly-nonzero coef */
875
temp = ((*block)[natural_order[k]] < 0) ? 0 : 1;
876
emit_bits_e(entropy, (unsigned int) temp, 1);
878
/* Emit buffered correction bits that must be associated with this code */
879
emit_buffered_bits(entropy, BR_buffer, BR);
880
BR_buffer = entropy->bit_buffer; /* BE bits are gone now */
882
r = 0; /* reset zero run length */
885
if (r > 0 || BR > 0) { /* If there are trailing zeroes, */
886
entropy->EOBRUN++; /* count an EOB */
887
entropy->BE += BR; /* concat my correction bits to older ones */
888
/* We force out the EOB if we risk either:
889
* 1. overflow of the EOB counter;
890
* 2. overflow of the correction bit buffer during the next MCU.
892
if (entropy->EOBRUN == 0x7FFF || entropy->BE > (MAX_CORR_BITS-DCTSIZE2+1))
893
emit_eobrun(entropy);
896
cinfo->dest->next_output_byte = entropy->next_output_byte;
897
cinfo->dest->free_in_buffer = entropy->free_in_buffer;
899
/* Update restart-interval state too */
900
if (cinfo->restart_interval) {
901
if (entropy->restarts_to_go == 0) {
902
entropy->restarts_to_go = cinfo->restart_interval;
903
entropy->next_restart_num++;
904
entropy->next_restart_num &= 7;
906
entropy->restarts_to_go--;
913
/* Encode a single block's worth of coefficients */
916
encode_one_block (working_state * state, JCOEFPTR block, int last_dc_val,
917
c_derived_tbl *dctbl, c_derived_tbl *actbl)
919
register int temp, temp2;
921
register int k, r, i;
922
int Se = state->cinfo->lim_Se;
923
const int * natural_order = state->cinfo->natural_order;
925
/* Encode the DC coefficient difference per section F.1.2.1 */
927
temp = temp2 = block[0] - last_dc_val;
930
temp = -temp; /* temp is abs value of input */
931
/* For a negative input, want temp2 = bitwise complement of abs(input) */
932
/* This code assumes we are on a two's complement machine */
936
/* Find the number of bits needed for the magnitude of the coefficient */
942
/* Check for out-of-range coefficient values.
943
* Since we're encoding a difference, the range limit is twice as much.
945
if (nbits > MAX_COEF_BITS+1)
946
ERREXIT(state->cinfo, JERR_BAD_DCT_COEF);
948
/* Emit the Huffman-coded symbol for the number of bits */
949
if (! emit_bits_s(state, dctbl->ehufco[nbits], dctbl->ehufsi[nbits]))
952
/* Emit that number of bits of the value, if positive, */
953
/* or the complement of its magnitude, if negative. */
954
if (nbits) /* emit_bits rejects calls with size 0 */
955
if (! emit_bits_s(state, (unsigned int) temp2, nbits))
958
/* Encode the AC coefficients per section F.1.2.2 */
960
r = 0; /* r = run length of zeros */
962
for (k = 1; k <= Se; k++) {
963
if ((temp = block[natural_order[k]]) == 0) {
966
/* if run length > 15, must emit special run-length-16 codes (0xF0) */
968
if (! emit_bits_s(state, actbl->ehufco[0xF0], actbl->ehufsi[0xF0]))
975
temp = -temp; /* temp is abs value of input */
976
/* This code assumes we are on a two's complement machine */
980
/* Find the number of bits needed for the magnitude of the coefficient */
981
nbits = 1; /* there must be at least one 1 bit */
984
/* Check for out-of-range coefficient values */
985
if (nbits > MAX_COEF_BITS)
986
ERREXIT(state->cinfo, JERR_BAD_DCT_COEF);
988
/* Emit Huffman symbol for run length / number of bits */
989
i = (r << 4) + nbits;
990
if (! emit_bits_s(state, actbl->ehufco[i], actbl->ehufsi[i]))
993
/* Emit that number of bits of the value, if positive, */
994
/* or the complement of its magnitude, if negative. */
995
if (! emit_bits_s(state, (unsigned int) temp2, nbits))
1002
/* If the last coef(s) were zero, emit an end-of-block code */
1004
if (! emit_bits_s(state, actbl->ehufco[0], actbl->ehufsi[0]))
1012
* Encode and output one MCU's worth of Huffman-compressed coefficients.
1016
encode_mcu_huff (j_compress_ptr cinfo, JBLOCKROW *MCU_data)
1018
huff_entropy_ptr entropy = (huff_entropy_ptr) cinfo->entropy;
1019
working_state state;
1021
jpeg_component_info * compptr;
1023
/* Load up working state */
1024
state.next_output_byte = cinfo->dest->next_output_byte;
1025
state.free_in_buffer = cinfo->dest->free_in_buffer;
1026
ASSIGN_STATE(state.cur, entropy->saved);
1027
state.cinfo = cinfo;
1029
/* Emit restart marker if needed */
1030
if (cinfo->restart_interval) {
1031
if (entropy->restarts_to_go == 0)
1032
if (! emit_restart_s(&state, entropy->next_restart_num))
1036
/* Encode the MCU data blocks */
1037
for (blkn = 0; blkn < cinfo->blocks_in_MCU; blkn++) {
1038
ci = cinfo->MCU_membership[blkn];
1039
compptr = cinfo->cur_comp_info[ci];
1040
if (! encode_one_block(&state,
1041
MCU_data[blkn][0], state.cur.last_dc_val[ci],
1042
entropy->dc_derived_tbls[compptr->dc_tbl_no],
1043
entropy->ac_derived_tbls[compptr->ac_tbl_no]))
1045
/* Update last_dc_val */
1046
state.cur.last_dc_val[ci] = MCU_data[blkn][0][0];
1049
/* Completed MCU, so update state */
1050
cinfo->dest->next_output_byte = state.next_output_byte;
1051
cinfo->dest->free_in_buffer = state.free_in_buffer;
1052
ASSIGN_STATE(entropy->saved, state.cur);
1054
/* Update restart-interval state too */
1055
if (cinfo->restart_interval) {
1056
if (entropy->restarts_to_go == 0) {
1057
entropy->restarts_to_go = cinfo->restart_interval;
1058
entropy->next_restart_num++;
1059
entropy->next_restart_num &= 7;
1061
entropy->restarts_to_go--;
1069
* Finish up at the end of a Huffman-compressed scan.
1073
finish_pass_huff (j_compress_ptr cinfo)
1075
huff_entropy_ptr entropy = (huff_entropy_ptr) cinfo->entropy;
1076
working_state state;
1078
if (cinfo->progressive_mode) {
1079
entropy->next_output_byte = cinfo->dest->next_output_byte;
1080
entropy->free_in_buffer = cinfo->dest->free_in_buffer;
1082
/* Flush out any buffered data */
1083
emit_eobrun(entropy);
1084
flush_bits_e(entropy);
1086
cinfo->dest->next_output_byte = entropy->next_output_byte;
1087
cinfo->dest->free_in_buffer = entropy->free_in_buffer;
1089
/* Load up working state ... flush_bits needs it */
1090
state.next_output_byte = cinfo->dest->next_output_byte;
1091
state.free_in_buffer = cinfo->dest->free_in_buffer;
1092
ASSIGN_STATE(state.cur, entropy->saved);
1093
state.cinfo = cinfo;
1095
/* Flush out the last data */
1096
if (! flush_bits_s(&state))
1097
ERREXIT(cinfo, JERR_CANT_SUSPEND);
1100
cinfo->dest->next_output_byte = state.next_output_byte;
1101
cinfo->dest->free_in_buffer = state.free_in_buffer;
1102
ASSIGN_STATE(entropy->saved, state.cur);
1108
* Huffman coding optimization.
1110
* We first scan the supplied data and count the number of uses of each symbol
1111
* that is to be Huffman-coded. (This process MUST agree with the code above.)
1112
* Then we build a Huffman coding tree for the observed counts.
1113
* Symbols which are not needed at all for the particular image are not
1114
* assigned any code, which saves space in the DHT marker as well as in
1115
* the compressed data.
1119
/* Process a single block's worth of coefficients */
1122
htest_one_block (j_compress_ptr cinfo, JCOEFPTR block, int last_dc_val,
1123
long dc_counts[], long ac_counts[])
1128
int Se = cinfo->lim_Se;
1129
const int * natural_order = cinfo->natural_order;
1131
/* Encode the DC coefficient difference per section F.1.2.1 */
1133
temp = block[0] - last_dc_val;
1137
/* Find the number of bits needed for the magnitude of the coefficient */
1143
/* Check for out-of-range coefficient values.
1144
* Since we're encoding a difference, the range limit is twice as much.
1146
if (nbits > MAX_COEF_BITS+1)
1147
ERREXIT(cinfo, JERR_BAD_DCT_COEF);
1149
/* Count the Huffman symbol for the number of bits */
1152
/* Encode the AC coefficients per section F.1.2.2 */
1154
r = 0; /* r = run length of zeros */
1156
for (k = 1; k <= Se; k++) {
1157
if ((temp = block[natural_order[k]]) == 0) {
1160
/* if run length > 15, must emit special run-length-16 codes (0xF0) */
1166
/* Find the number of bits needed for the magnitude of the coefficient */
1170
/* Find the number of bits needed for the magnitude of the coefficient */
1171
nbits = 1; /* there must be at least one 1 bit */
1172
while ((temp >>= 1))
1174
/* Check for out-of-range coefficient values */
1175
if (nbits > MAX_COEF_BITS)
1176
ERREXIT(cinfo, JERR_BAD_DCT_COEF);
1178
/* Count Huffman symbol for run length / number of bits */
1179
ac_counts[(r << 4) + nbits]++;
1185
/* If the last coef(s) were zero, emit an end-of-block code */
1192
* Trial-encode one MCU's worth of Huffman-compressed coefficients.
1193
* No data is actually output, so no suspension return is possible.
1197
encode_mcu_gather (j_compress_ptr cinfo, JBLOCKROW *MCU_data)
1199
huff_entropy_ptr entropy = (huff_entropy_ptr) cinfo->entropy;
1201
jpeg_component_info * compptr;
1203
/* Take care of restart intervals if needed */
1204
if (cinfo->restart_interval) {
1205
if (entropy->restarts_to_go == 0) {
1206
/* Re-initialize DC predictions to 0 */
1207
for (ci = 0; ci < cinfo->comps_in_scan; ci++)
1208
entropy->saved.last_dc_val[ci] = 0;
1209
/* Update restart state */
1210
entropy->restarts_to_go = cinfo->restart_interval;
1212
entropy->restarts_to_go--;
1215
for (blkn = 0; blkn < cinfo->blocks_in_MCU; blkn++) {
1216
ci = cinfo->MCU_membership[blkn];
1217
compptr = cinfo->cur_comp_info[ci];
1218
htest_one_block(cinfo, MCU_data[blkn][0], entropy->saved.last_dc_val[ci],
1219
entropy->dc_count_ptrs[compptr->dc_tbl_no],
1220
entropy->ac_count_ptrs[compptr->ac_tbl_no]);
1221
entropy->saved.last_dc_val[ci] = MCU_data[blkn][0][0];
1229
* Generate the best Huffman code table for the given counts, fill htbl.
1231
* The JPEG standard requires that no symbol be assigned a codeword of all
1232
* one bits (so that padding bits added at the end of a compressed segment
1233
* can't look like a valid code). Because of the canonical ordering of
1234
* codewords, this just means that there must be an unused slot in the
1235
* longest codeword length category. Section K.2 of the JPEG spec suggests
1236
* reserving such a slot by pretending that symbol 256 is a valid symbol
1237
* with count 1. In theory that's not optimal; giving it count zero but
1238
* including it in the symbol set anyway should give a better Huffman code.
1239
* But the theoretically better code actually seems to come out worse in
1240
* practice, because it produces more all-ones bytes (which incur stuffed
1241
* zero bytes in the final file). In any case the difference is tiny.
1243
* The JPEG standard requires Huffman codes to be no more than 16 bits long.
1244
* If some symbols have a very small but nonzero probability, the Huffman tree
1245
* must be adjusted to meet the code length restriction. We currently use
1246
* the adjustment method suggested in JPEG section K.2. This method is *not*
1247
* optimal; it may not choose the best possible limited-length code. But
1248
* typically only very-low-frequency symbols will be given less-than-optimal
1249
* lengths, so the code is almost optimal. Experimental comparisons against
1250
* an optimal limited-length-code algorithm indicate that the difference is
1251
* microscopic --- usually less than a hundredth of a percent of total size.
1252
* So the extra complexity of an optimal algorithm doesn't seem worthwhile.
1256
jpeg_gen_optimal_table (j_compress_ptr cinfo, JHUFF_TBL * htbl, long freq[])
1258
#define MAX_CLEN 32 /* assumed maximum initial code length */
1259
UINT8 bits[MAX_CLEN+1]; /* bits[k] = # of symbols with code length k */
1260
int codesize[257]; /* codesize[k] = code length of symbol k */
1261
int others[257]; /* next symbol in current branch of tree */
1266
/* This algorithm is explained in section K.2 of the JPEG standard */
1268
MEMZERO(bits, SIZEOF(bits));
1269
MEMZERO(codesize, SIZEOF(codesize));
1270
for (i = 0; i < 257; i++)
1271
others[i] = -1; /* init links to empty */
1273
freq[256] = 1; /* make sure 256 has a nonzero count */
1274
/* Including the pseudo-symbol 256 in the Huffman procedure guarantees
1275
* that no real symbol is given code-value of all ones, because 256
1276
* will be placed last in the largest codeword category.
1279
/* Huffman's basic algorithm to assign optimal code lengths to symbols */
1282
/* Find the smallest nonzero frequency, set c1 = its symbol */
1283
/* In case of ties, take the larger symbol number */
1286
for (i = 0; i <= 256; i++) {
1287
if (freq[i] && freq[i] <= v) {
1293
/* Find the next smallest nonzero frequency, set c2 = its symbol */
1294
/* In case of ties, take the larger symbol number */
1297
for (i = 0; i <= 256; i++) {
1298
if (freq[i] && freq[i] <= v && i != c1) {
1304
/* Done if we've merged everything into one frequency */
1308
/* Else merge the two counts/trees */
1309
freq[c1] += freq[c2];
1312
/* Increment the codesize of everything in c1's tree branch */
1314
while (others[c1] >= 0) {
1319
others[c1] = c2; /* chain c2 onto c1's tree branch */
1321
/* Increment the codesize of everything in c2's tree branch */
1323
while (others[c2] >= 0) {
1329
/* Now count the number of symbols of each code length */
1330
for (i = 0; i <= 256; i++) {
1332
/* The JPEG standard seems to think that this can't happen, */
1333
/* but I'm paranoid... */
1334
if (codesize[i] > MAX_CLEN)
1335
ERREXIT(cinfo, JERR_HUFF_CLEN_OVERFLOW);
1337
bits[codesize[i]]++;
1341
/* JPEG doesn't allow symbols with code lengths over 16 bits, so if the pure
1342
* Huffman procedure assigned any such lengths, we must adjust the coding.
1343
* Here is what the JPEG spec says about how this next bit works:
1344
* Since symbols are paired for the longest Huffman code, the symbols are
1345
* removed from this length category two at a time. The prefix for the pair
1346
* (which is one bit shorter) is allocated to one of the pair; then,
1347
* skipping the BITS entry for that prefix length, a code word from the next
1348
* shortest nonzero BITS entry is converted into a prefix for two code words
1352
for (i = MAX_CLEN; i > 16; i--) {
1353
while (bits[i] > 0) {
1354
j = i - 2; /* find length of new prefix to be used */
1355
while (bits[j] == 0)
1358
bits[i] -= 2; /* remove two symbols */
1359
bits[i-1]++; /* one goes in this length */
1360
bits[j+1] += 2; /* two new symbols in this length */
1361
bits[j]--; /* symbol of this length is now a prefix */
1365
/* Remove the count for the pseudo-symbol 256 from the largest codelength */
1366
while (bits[i] == 0) /* find largest codelength still in use */
1370
/* Return final symbol counts (only for lengths 0..16) */
1371
MEMCOPY(htbl->bits, bits, SIZEOF(htbl->bits));
1373
/* Return a list of the symbols sorted by code length */
1374
/* It's not real clear to me why we don't need to consider the codelength
1375
* changes made above, but the JPEG spec seems to think this works.
1378
for (i = 1; i <= MAX_CLEN; i++) {
1379
for (j = 0; j <= 255; j++) {
1380
if (codesize[j] == i) {
1381
htbl->huffval[p] = (UINT8) j;
1387
/* Set sent_table FALSE so updated table will be written to JPEG file. */
1388
htbl->sent_table = FALSE;
1393
* Finish up a statistics-gathering pass and create the new Huffman tables.
1397
finish_pass_gather (j_compress_ptr cinfo)
1399
huff_entropy_ptr entropy = (huff_entropy_ptr) cinfo->entropy;
1401
jpeg_component_info * compptr;
1402
JHUFF_TBL **htblptr;
1403
boolean did_dc[NUM_HUFF_TBLS];
1404
boolean did_ac[NUM_HUFF_TBLS];
1406
/* It's important not to apply jpeg_gen_optimal_table more than once
1407
* per table, because it clobbers the input frequency counts!
1409
if (cinfo->progressive_mode)
1410
/* Flush out buffered data (all we care about is counting the EOB symbol) */
1411
emit_eobrun(entropy);
1413
MEMZERO(did_dc, SIZEOF(did_dc));
1414
MEMZERO(did_ac, SIZEOF(did_ac));
1416
for (ci = 0; ci < cinfo->comps_in_scan; ci++) {
1417
compptr = cinfo->cur_comp_info[ci];
1418
/* DC needs no table for refinement scan */
1419
if (cinfo->Ss == 0 && cinfo->Ah == 0) {
1420
tbl = compptr->dc_tbl_no;
1421
if (! did_dc[tbl]) {
1422
htblptr = & cinfo->dc_huff_tbl_ptrs[tbl];
1423
if (*htblptr == NULL)
1424
*htblptr = jpeg_alloc_huff_table((j_common_ptr) cinfo);
1425
jpeg_gen_optimal_table(cinfo, *htblptr, entropy->dc_count_ptrs[tbl]);
1429
/* AC needs no table when not present */
1431
tbl = compptr->ac_tbl_no;
1432
if (! did_ac[tbl]) {
1433
htblptr = & cinfo->ac_huff_tbl_ptrs[tbl];
1434
if (*htblptr == NULL)
1435
*htblptr = jpeg_alloc_huff_table((j_common_ptr) cinfo);
1436
jpeg_gen_optimal_table(cinfo, *htblptr, entropy->ac_count_ptrs[tbl]);
1445
* Initialize for a Huffman-compressed scan.
1446
* If gather_statistics is TRUE, we do not output anything during the scan,
1447
* just count the Huffman symbols used and generate Huffman code tables.
1451
start_pass_huff (j_compress_ptr cinfo, boolean gather_statistics)
1453
huff_entropy_ptr entropy = (huff_entropy_ptr) cinfo->entropy;
1455
jpeg_component_info * compptr;
1457
if (gather_statistics)
1458
entropy->pub.finish_pass = finish_pass_gather;
1460
entropy->pub.finish_pass = finish_pass_huff;
1462
if (cinfo->progressive_mode) {
1463
entropy->cinfo = cinfo;
1464
entropy->gather_statistics = gather_statistics;
1466
/* We assume jcmaster.c already validated the scan parameters. */
1468
/* Select execution routine */
1469
if (cinfo->Ah == 0) {
1471
entropy->pub.encode_mcu = encode_mcu_DC_first;
1473
entropy->pub.encode_mcu = encode_mcu_AC_first;
1476
entropy->pub.encode_mcu = encode_mcu_DC_refine;
1478
entropy->pub.encode_mcu = encode_mcu_AC_refine;
1479
/* AC refinement needs a correction bit buffer */
1480
if (entropy->bit_buffer == NULL)
1481
entropy->bit_buffer = (char *)
1482
(*cinfo->mem->alloc_small) ((j_common_ptr) cinfo, JPOOL_IMAGE,
1483
MAX_CORR_BITS * SIZEOF(char));
1487
/* Initialize AC stuff */
1488
entropy->ac_tbl_no = cinfo->cur_comp_info[0]->ac_tbl_no;
1489
entropy->EOBRUN = 0;
1492
if (gather_statistics)
1493
entropy->pub.encode_mcu = encode_mcu_gather;
1495
entropy->pub.encode_mcu = encode_mcu_huff;
1498
for (ci = 0; ci < cinfo->comps_in_scan; ci++) {
1499
compptr = cinfo->cur_comp_info[ci];
1500
/* DC needs no table for refinement scan */
1501
if (cinfo->Ss == 0 && cinfo->Ah == 0) {
1502
tbl = compptr->dc_tbl_no;
1503
if (gather_statistics) {
1504
/* Check for invalid table index */
1505
/* (make_c_derived_tbl does this in the other path) */
1506
if (tbl < 0 || tbl >= NUM_HUFF_TBLS)
1507
ERREXIT1(cinfo, JERR_NO_HUFF_TABLE, tbl);
1508
/* Allocate and zero the statistics tables */
1509
/* Note that jpeg_gen_optimal_table expects 257 entries in each table! */
1510
if (entropy->dc_count_ptrs[tbl] == NULL)
1511
entropy->dc_count_ptrs[tbl] = (long *)
1512
(*cinfo->mem->alloc_small) ((j_common_ptr) cinfo, JPOOL_IMAGE,
1513
257 * SIZEOF(long));
1514
MEMZERO(entropy->dc_count_ptrs[tbl], 257 * SIZEOF(long));
1516
/* Compute derived values for Huffman tables */
1517
/* We may do this more than once for a table, but it's not expensive */
1518
jpeg_make_c_derived_tbl(cinfo, TRUE, tbl,
1519
& entropy->dc_derived_tbls[tbl]);
1521
/* Initialize DC predictions to 0 */
1522
entropy->saved.last_dc_val[ci] = 0;
1524
/* AC needs no table when not present */
1526
tbl = compptr->ac_tbl_no;
1527
if (gather_statistics) {
1528
if (tbl < 0 || tbl >= NUM_HUFF_TBLS)
1529
ERREXIT1(cinfo, JERR_NO_HUFF_TABLE, tbl);
1530
if (entropy->ac_count_ptrs[tbl] == NULL)
1531
entropy->ac_count_ptrs[tbl] = (long *)
1532
(*cinfo->mem->alloc_small) ((j_common_ptr) cinfo, JPOOL_IMAGE,
1533
257 * SIZEOF(long));
1534
MEMZERO(entropy->ac_count_ptrs[tbl], 257 * SIZEOF(long));
1536
jpeg_make_c_derived_tbl(cinfo, FALSE, tbl,
1537
& entropy->ac_derived_tbls[tbl]);
1542
/* Initialize bit buffer to empty */
1543
entropy->saved.put_buffer = 0;
1544
entropy->saved.put_bits = 0;
1546
/* Initialize restart stuff */
1547
entropy->restarts_to_go = cinfo->restart_interval;
1548
entropy->next_restart_num = 0;
1553
* Module initialization routine for Huffman entropy encoding.
1557
jinit_huff_encoder (j_compress_ptr cinfo)
1559
huff_entropy_ptr entropy;
1562
entropy = (huff_entropy_ptr)
1563
(*cinfo->mem->alloc_small) ((j_common_ptr) cinfo, JPOOL_IMAGE,
1564
SIZEOF(huff_entropy_encoder));
1565
cinfo->entropy = (struct jpeg_entropy_encoder *) entropy;
1566
entropy->pub.start_pass = start_pass_huff;
1568
/* Mark tables unallocated */
1569
for (i = 0; i < NUM_HUFF_TBLS; i++) {
1570
entropy->dc_derived_tbls[i] = entropy->ac_derived_tbls[i] = NULL;
1571
entropy->dc_count_ptrs[i] = entropy->ac_count_ptrs[i] = NULL;
1574
if (cinfo->progressive_mode)
1575
entropy->bit_buffer = NULL; /* needed only in AC refinement scan */
added
removed
source/Irrlicht/jpeglib/jchuff.c
