1 /* 2 * jcphuff.c 3 * 4 * This file was part of the Independent JPEG Group's software: 5 * Copyright (C) 1995-1997, Thomas G. Lane. 6 * libjpeg-turbo Modifications: 7 * Copyright (C) 2015, D. R. Commander. 8 * For conditions of distribution and use, see the accompanying README.ijg 9 * file. 10 * 11 * This file contains Huffman entropy encoding routines for progressive JPEG. 12 * 13 * We do not support output suspension in this module, since the library 14 * currently does not allow multiple-scan files to be written with output 15 * suspension. 16 */ 17 18 #define JPEG_INTERNALS 19 #include "jinclude.h" 20 #include "jpeglib.h" 21 #include "jchuff.h" /* Declarations shared with jchuff.c */ 22 23 #ifdef C_PROGRESSIVE_SUPPORTED 24 25 /* Expanded entropy encoder object for progressive Huffman encoding. */ 26 27 typedef struct { 28 struct jpeg_entropy_encoder pub; /* public fields */ 29 30 /* Mode flag: TRUE for optimization, FALSE for actual data output */ 31 boolean gather_statistics; 32 33 /* Bit-level coding status. 34 * next_output_byte/free_in_buffer are local copies of cinfo->dest fields. 35 */ 36 JOCTET *next_output_byte; /* => next byte to write in buffer */ 37 size_t free_in_buffer; /* # of byte spaces remaining in buffer */ 38 size_t put_buffer; /* current bit-accumulation buffer */ 39 int put_bits; /* # of bits now in it */ 40 j_compress_ptr cinfo; /* link to cinfo (needed for dump_buffer) */ 41 42 /* Coding status for DC components */ 43 int last_dc_val[MAX_COMPS_IN_SCAN]; /* last DC coef for each component */ 44 45 /* Coding status for AC components */ 46 int ac_tbl_no; /* the table number of the single component */ 47 unsigned int EOBRUN; /* run length of EOBs */ 48 unsigned int BE; /* # of buffered correction bits before MCU */ 49 char *bit_buffer; /* buffer for correction bits (1 per char) */ 50 /* packing correction bits tightly would save some space but cost time... */ 51 52 unsigned int restarts_to_go; /* MCUs left in this restart interval */ 53 int next_restart_num; /* next restart number to write (0-7) */ 54 55 /* Pointers to derived tables (these workspaces have image lifespan). 56 * Since any one scan codes only DC or only AC, we only need one set 57 * of tables, not one for DC and one for AC. 58 */ 59 c_derived_tbl *derived_tbls[NUM_HUFF_TBLS]; 60 61 /* Statistics tables for optimization; again, one set is enough */ 62 long *count_ptrs[NUM_HUFF_TBLS]; 63 } phuff_entropy_encoder; 64 65 typedef phuff_entropy_encoder *phuff_entropy_ptr; 66 67 /* MAX_CORR_BITS is the number of bits the AC refinement correction-bit 68 * buffer can hold. Larger sizes may slightly improve compression, but 69 * 1000 is already well into the realm of overkill. 70 * The minimum safe size is 64 bits. 71 */ 72 73 #define MAX_CORR_BITS 1000 /* Max # of correction bits I can buffer */ 74 75 /* IRIGHT_SHIFT is like RIGHT_SHIFT, but works on int rather than JLONG. 76 * We assume that int right shift is unsigned if JLONG right shift is, 77 * which should be safe. 78 */ 79 80 #ifdef RIGHT_SHIFT_IS_UNSIGNED 81 #define ISHIFT_TEMPS int ishift_temp; 82 #define IRIGHT_SHIFT(x,shft) \ 83 ((ishift_temp = (x)) < 0 ? \ 84 (ishift_temp >> (shft)) | ((~0) << (16-(shft))) : \ 85 (ishift_temp >> (shft))) 86 #else 87 #define ISHIFT_TEMPS 88 #define IRIGHT_SHIFT(x,shft) ((x) >> (shft)) 89 #endif 90 91 /* Forward declarations */ 92 METHODDEF(boolean) encode_mcu_DC_first (j_compress_ptr cinfo, 93 JBLOCKROW *MCU_data); 94 METHODDEF(boolean) encode_mcu_AC_first (j_compress_ptr cinfo, 95 JBLOCKROW *MCU_data); 96 METHODDEF(boolean) encode_mcu_DC_refine (j_compress_ptr cinfo, 97 JBLOCKROW *MCU_data); 98 METHODDEF(boolean) encode_mcu_AC_refine (j_compress_ptr cinfo, 99 JBLOCKROW *MCU_data); 100 METHODDEF(void) finish_pass_phuff (j_compress_ptr cinfo); 101 METHODDEF(void) finish_pass_gather_phuff (j_compress_ptr cinfo); 102 103 104 /* 105 * Initialize for a Huffman-compressed scan using progressive JPEG. 106 */ 107 108 METHODDEF(void) 109 start_pass_phuff (j_compress_ptr cinfo, boolean gather_statistics) 110 { 111 phuff_entropy_ptr entropy = (phuff_entropy_ptr) cinfo->entropy; 112 boolean is_DC_band; 113 int ci, tbl; 114 jpeg_component_info *compptr; 115 116 entropy->cinfo = cinfo; 117 entropy->gather_statistics = gather_statistics; 118 119 is_DC_band = (cinfo->Ss == 0); 120 121 /* We assume jcmaster.c already validated the scan parameters. */ 122 123 /* Select execution routines */ 124 if (cinfo->Ah == 0) { 125 if (is_DC_band) 126 entropy->pub.encode_mcu = encode_mcu_DC_first; 127 else 128 entropy->pub.encode_mcu = encode_mcu_AC_first; 129 } else { 130 if (is_DC_band) 131 entropy->pub.encode_mcu = encode_mcu_DC_refine; 132 else { 133 entropy->pub.encode_mcu = encode_mcu_AC_refine; 134 /* AC refinement needs a correction bit buffer */ 135 if (entropy->bit_buffer == NULL) 136 entropy->bit_buffer = (char *) 137 (*cinfo->mem->alloc_small) ((j_common_ptr) cinfo, JPOOL_IMAGE, 138 MAX_CORR_BITS * sizeof(char)); 139 } 140 } 141 if (gather_statistics) 142 entropy->pub.finish_pass = finish_pass_gather_phuff; 143 else 144 entropy->pub.finish_pass = finish_pass_phuff; 145 146 /* Only DC coefficients may be interleaved, so cinfo->comps_in_scan = 1 147 * for AC coefficients. 148 */ 149 for (ci = 0; ci < cinfo->comps_in_scan; ci++) { 150 compptr = cinfo->cur_comp_info[ci]; 151 /* Initialize DC predictions to 0 */ 152 entropy->last_dc_val[ci] = 0; 153 /* Get table index */ 154 if (is_DC_band) { 155 if (cinfo->Ah != 0) /* DC refinement needs no table */ 156 continue; 157 tbl = compptr->dc_tbl_no; 158 } else { 159 entropy->ac_tbl_no = tbl = compptr->ac_tbl_no; 160 } 161 if (gather_statistics) { 162 /* Check for invalid table index */ 163 /* (make_c_derived_tbl does this in the other path) */ 164 if (tbl < 0 || tbl >= NUM_HUFF_TBLS) 165 ERREXIT1(cinfo, JERR_NO_HUFF_TABLE, tbl); 166 /* Allocate and zero the statistics tables */ 167 /* Note that jpeg_gen_optimal_table expects 257 entries in each table! */ 168 if (entropy->count_ptrs[tbl] == NULL) 169 entropy->count_ptrs[tbl] = (long *) 170 (*cinfo->mem->alloc_small) ((j_common_ptr) cinfo, JPOOL_IMAGE, 171 257 * sizeof(long)); 172 MEMZERO(entropy->count_ptrs[tbl], 257 * sizeof(long)); 173 } else { 174 /* Compute derived values for Huffman table */ 175 /* We may do this more than once for a table, but it's not expensive */ 176 jpeg_make_c_derived_tbl(cinfo, is_DC_band, tbl, 177 & entropy->derived_tbls[tbl]); 178 } 179 } 180 181 /* Initialize AC stuff */ 182 entropy->EOBRUN = 0; 183 entropy->BE = 0; 184 185 /* Initialize bit buffer to empty */ 186 entropy->put_buffer = 0; 187 entropy->put_bits = 0; 188 189 /* Initialize restart stuff */ 190 entropy->restarts_to_go = cinfo->restart_interval; 191 entropy->next_restart_num = 0; 192 } 193 194 195 /* Outputting bytes to the file. 196 * NB: these must be called only when actually outputting, 197 * that is, entropy->gather_statistics == FALSE. 198 */ 199 200 /* Emit a byte */ 201 #define emit_byte(entropy,val) \ 202 { *(entropy)->next_output_byte++ = (JOCTET) (val); \ 203 if (--(entropy)->free_in_buffer == 0) \ 204 dump_buffer(entropy); } 205 206 207 LOCAL(void) 208 dump_buffer (phuff_entropy_ptr entropy) 209 /* Empty the output buffer; we do not support suspension in this module. */ 210 { 211 struct jpeg_destination_mgr *dest = entropy->cinfo->dest; 212 213 if (! (*dest->empty_output_buffer) (entropy->cinfo)) 214 ERREXIT(entropy->cinfo, JERR_CANT_SUSPEND); 215 /* After a successful buffer dump, must reset buffer pointers */ 216 entropy->next_output_byte = dest->next_output_byte; 217 entropy->free_in_buffer = dest->free_in_buffer; 218 } 219 220 221 /* Outputting bits to the file */ 222 223 /* Only the right 24 bits of put_buffer are used; the valid bits are 224 * left-justified in this part. At most 16 bits can be passed to emit_bits 225 * in one call, and we never retain more than 7 bits in put_buffer 226 * between calls, so 24 bits are sufficient. 227 */ 228 229 LOCAL(void) 230 emit_bits (phuff_entropy_ptr entropy, unsigned int code, int size) 231 /* Emit some bits, unless we are in gather mode */ 232 { 233 /* This routine is heavily used, so it's worth coding tightly. */ 234 register size_t put_buffer = (size_t) code; 235 register int put_bits = entropy->put_bits; 236 237 /* if size is 0, caller used an invalid Huffman table entry */ 238 if (size == 0) 239 ERREXIT(entropy->cinfo, JERR_HUFF_MISSING_CODE); 240 241 if (entropy->gather_statistics) 242 return; /* do nothing if we're only getting stats */ 243 244 put_buffer &= (((size_t) 1)<<size) - 1; /* mask off any extra bits in code */ 245 246 put_bits += size; /* new number of bits in buffer */ 247 248 put_buffer <<= 24 - put_bits; /* align incoming bits */ 249 250 put_buffer |= entropy->put_buffer; /* and merge with old buffer contents */ 251 252 while (put_bits >= 8) { 253 int c = (int) ((put_buffer >> 16) & 0xFF); 254 255 emit_byte(entropy, c); 256 if (c == 0xFF) { /* need to stuff a zero byte? */ 257 emit_byte(entropy, 0); 258 } 259 put_buffer <<= 8; 260 put_bits -= 8; 261 } 262 263 entropy->put_buffer = put_buffer; /* update variables */ 264 entropy->put_bits = put_bits; 265 } 266 267 268 LOCAL(void) 269 flush_bits (phuff_entropy_ptr entropy) 270 { 271 emit_bits(entropy, 0x7F, 7); /* fill any partial byte with ones */ 272 entropy->put_buffer = 0; /* and reset bit-buffer to empty */ 273 entropy->put_bits = 0; 274 } 275 276 277 /* 278 * Emit (or just count) a Huffman symbol. 279 */ 280 281 LOCAL(void) 282 emit_symbol (phuff_entropy_ptr entropy, int tbl_no, int symbol) 283 { 284 if (entropy->gather_statistics) 285 entropy->count_ptrs[tbl_no][symbol]++; 286 else { 287 c_derived_tbl *tbl = entropy->derived_tbls[tbl_no]; 288 emit_bits(entropy, tbl->ehufco[symbol], tbl->ehufsi[symbol]); 289 } 290 } 291 292 293 /* 294 * Emit bits from a correction bit buffer. 295 */ 296 297 LOCAL(void) 298 emit_buffered_bits (phuff_entropy_ptr entropy, char *bufstart, 299 unsigned int nbits) 300 { 301 if (entropy->gather_statistics) 302 return; /* no real work */ 303 304 while (nbits > 0) { 305 emit_bits(entropy, (unsigned int) (*bufstart), 1); 306 bufstart++; 307 nbits--; 308 } 309 } 310 311 312 /* 313 * Emit any pending EOBRUN symbol. 314 */ 315 316 LOCAL(void) 317 emit_eobrun (phuff_entropy_ptr entropy) 318 { 319 register int temp, nbits; 320 321 if (entropy->EOBRUN > 0) { /* if there is any pending EOBRUN */ 322 temp = entropy->EOBRUN; 323 nbits = 0; 324 while ((temp >>= 1)) 325 nbits++; 326 /* safety check: shouldn't happen given limited correction-bit buffer */ 327 if (nbits > 14) 328 ERREXIT(entropy->cinfo, JERR_HUFF_MISSING_CODE); 329 330 emit_symbol(entropy, entropy->ac_tbl_no, nbits << 4); 331 if (nbits) 332 emit_bits(entropy, entropy->EOBRUN, nbits); 333 334 entropy->EOBRUN = 0; 335 336 /* Emit any buffered correction bits */ 337 emit_buffered_bits(entropy, entropy->bit_buffer, entropy->BE); 338 entropy->BE = 0; 339 } 340 } 341 342 343 /* 344 * Emit a restart marker & resynchronize predictions. 345 */ 346 347 LOCAL(void) 348 emit_restart (phuff_entropy_ptr entropy, int restart_num) 349 { 350 int ci; 351 352 emit_eobrun(entropy); 353 354 if (! entropy->gather_statistics) { 355 flush_bits(entropy); 356 emit_byte(entropy, 0xFF); 357 emit_byte(entropy, JPEG_RST0 + restart_num); 358 } 359 360 if (entropy->cinfo->Ss == 0) { 361 /* Re-initialize DC predictions to 0 */ 362 for (ci = 0; ci < entropy->cinfo->comps_in_scan; ci++) 363 entropy->last_dc_val[ci] = 0; 364 } else { 365 /* Re-initialize all AC-related fields to 0 */ 366 entropy->EOBRUN = 0; 367 entropy->BE = 0; 368 } 369 } 370 371 372 /* 373 * MCU encoding for DC initial scan (either spectral selection, 374 * or first pass of successive approximation). 375 */ 376 377 METHODDEF(boolean) 378 encode_mcu_DC_first (j_compress_ptr cinfo, JBLOCKROW *MCU_data) 379 { 380 phuff_entropy_ptr entropy = (phuff_entropy_ptr) cinfo->entropy; 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->blocks_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) 465 encode_mcu_AC_first (j_compress_ptr cinfo, JBLOCKROW *MCU_data) 466 { 467 phuff_entropy_ptr entropy = (phuff_entropy_ptr) cinfo->entropy; 468 register int temp, temp2; 469 register int nbits; 470 register int r, k; 471 int Se = cinfo->Se; 472 int Al = cinfo->Al; 473 JBLOCKROW block; 474 475 entropy->next_output_byte = cinfo->dest->next_output_byte; 476 entropy->free_in_buffer = cinfo->dest->free_in_buffer; 477 478 /* Emit restart marker if needed */ 479 if (cinfo->restart_interval) 480 if (entropy->restarts_to_go == 0) 481 emit_restart(entropy, entropy->next_restart_num); 482 483 /* Encode the MCU data block */ 484 block = MCU_data[0]; 485 486 /* Encode the AC coefficients per section G.1.2.2, fig. G.3 */ 487 488 r = 0; /* r = run length of zeros */ 489 490 for (k = cinfo->Ss; k <= Se; k++) { 491 if ((temp = (*block)[jpeg_natural_order[k]]) == 0) { 492 r++; 493 continue; 494 } 495 /* We must apply the point transform by Al. For AC coefficients this 496 * is an integer division with rounding towards 0. To do this portably 497 * in C, we shift after obtaining the absolute value; so the code is 498 * interwoven with finding the abs value (temp) and output bits (temp2). 499 */ 500 if (temp < 0) { 501 temp = -temp; /* temp is abs value of input */ 502 temp >>= Al; /* apply the point transform */ 503 /* For a negative coef, want temp2 = bitwise complement of abs(coef) */ 504 temp2 = ~temp; 505 } else { 506 temp >>= Al; /* apply the point transform */ 507 temp2 = temp; 508 } 509 /* Watch out for case that nonzero coef is zero after point transform */ 510 if (temp == 0) { 511 r++; 512 continue; 513 } 514 515 /* Emit any pending EOBRUN */ 516 if (entropy->EOBRUN > 0) 517 emit_eobrun(entropy); 518 /* if run length > 15, must emit special run-length-16 codes (0xF0) */ 519 while (r > 15) { 520 emit_symbol(entropy, entropy->ac_tbl_no, 0xF0); 521 r -= 16; 522 } 523 524 /* Find the number of bits needed for the magnitude of the coefficient */ 525 nbits = 1; /* there must be at least one 1 bit */ 526 while ((temp >>= 1)) 527 nbits++; 528 /* Check for out-of-range coefficient values */ 529 if (nbits > MAX_COEF_BITS) 530 ERREXIT(cinfo, JERR_BAD_DCT_COEF); 531 532 /* Count/emit Huffman symbol for run length / number of bits */ 533 emit_symbol(entropy, entropy->ac_tbl_no, (r << 4) + nbits); 534 535 /* Emit that number of bits of the value, if positive, */ 536 /* or the complement of its magnitude, if negative. */ 537 emit_bits(entropy, (unsigned int) temp2, nbits); 538 539 r = 0; /* reset zero run length */ 540 } 541 542 if (r > 0) { /* If there are trailing zeroes, */ 543 entropy->EOBRUN++; /* count an EOB */ 544 if (entropy->EOBRUN == 0x7FFF) 545 emit_eobrun(entropy); /* force it out to avoid overflow */ 546 } 547 548 cinfo->dest->next_output_byte = entropy->next_output_byte; 549 cinfo->dest->free_in_buffer = entropy->free_in_buffer; 550 551 /* Update restart-interval state too */ 552 if (cinfo->restart_interval) { 553 if (entropy->restarts_to_go == 0) { 554 entropy->restarts_to_go = cinfo->restart_interval; 555 entropy->next_restart_num++; 556 entropy->next_restart_num &= 7; 557 } 558 entropy->restarts_to_go--; 559 } 560 561 return TRUE; 562 } 563 564 565 /* 566 * MCU encoding for DC successive approximation refinement scan. 567 * Note: we assume such scans can be multi-component, although the spec 568 * is not very clear on the point. 569 */ 570 571 METHODDEF(boolean) 572 encode_mcu_DC_refine (j_compress_ptr cinfo, JBLOCKROW *MCU_data) 573 { 574 phuff_entropy_ptr entropy = (phuff_entropy_ptr) cinfo->entropy; 575 register int temp; 576 int blkn; 577 int Al = cinfo->Al; 578 JBLOCKROW block; 579 580 entropy->next_output_byte = cinfo->dest->next_output_byte; 581 entropy->free_in_buffer = cinfo->dest->free_in_buffer; 582 583 /* Emit restart marker if needed */ 584 if (cinfo->restart_interval) 585 if (entropy->restarts_to_go == 0) 586 emit_restart(entropy, entropy->next_restart_num); 587 588 /* Encode the MCU data blocks */ 589 for (blkn = 0; blkn < cinfo->blocks_in_MCU; blkn++) { 590 block = MCU_data[blkn]; 591 592 /* We simply emit the Al'th bit of the DC coefficient value. */ 593 temp = (*block)[0]; 594 emit_bits(entropy, (unsigned int) (temp >> Al), 1); 595 } 596 597 cinfo->dest->next_output_byte = entropy->next_output_byte; 598 cinfo->dest->free_in_buffer = entropy->free_in_buffer; 599 600 /* Update restart-interval state too */ 601 if (cinfo->restart_interval) { 602 if (entropy->restarts_to_go == 0) { 603 entropy->restarts_to_go = cinfo->restart_interval; 604 entropy->next_restart_num++; 605 entropy->next_restart_num &= 7; 606 } 607 entropy->restarts_to_go--; 608 } 609 610 return TRUE; 611 } 612 613 614 /* 615 * MCU encoding for AC successive approximation refinement scan. 616 */ 617 618 METHODDEF(boolean) 619 encode_mcu_AC_refine (j_compress_ptr cinfo, JBLOCKROW *MCU_data) 620 { 621 phuff_entropy_ptr entropy = (phuff_entropy_ptr) cinfo->entropy; 622 register int temp; 623 register int r, k; 624 int EOB; 625 char *BR_buffer; 626 unsigned int BR; 627 int Se = cinfo->Se; 628 int Al = cinfo->Al; 629 JBLOCKROW block; 630 int absvalues[DCTSIZE2]; 631 632 entropy->next_output_byte = cinfo->dest->next_output_byte; 633 entropy->free_in_buffer = cinfo->dest->free_in_buffer; 634 635 /* Emit restart marker if needed */ 636 if (cinfo->restart_interval) 637 if (entropy->restarts_to_go == 0) 638 emit_restart(entropy, entropy->next_restart_num); 639 640 /* Encode the MCU data block */ 641 block = MCU_data[0]; 642 643 /* It is convenient to make a pre-pass to determine the transformed 644 * coefficients' absolute values and the EOB position. 645 */ 646 EOB = 0; 647 for (k = cinfo->Ss; k <= Se; k++) { 648 temp = (*block)[jpeg_natural_order[k]]; 649 /* We must apply the point transform by Al. For AC coefficients this 650 * is an integer division with rounding towards 0. To do this portably 651 * in C, we shift after obtaining the absolute value. 652 */ 653 if (temp < 0) 654 temp = -temp; /* temp is abs value of input */ 655 temp >>= Al; /* apply the point transform */ 656 absvalues[k] = temp; /* save abs value for main pass */ 657 if (temp == 1) 658 EOB = k; /* EOB = index of last newly-nonzero coef */ 659 } 660 661 /* Encode the AC coefficients per section G.1.2.3, fig. G.7 */ 662 663 r = 0; /* r = run length of zeros */ 664 BR = 0; /* BR = count of buffered bits added now */ 665 BR_buffer = entropy->bit_buffer + entropy->BE; /* Append bits to buffer */ 666 667 for (k = cinfo->Ss; k <= Se; k++) { 668 if ((temp = absvalues[k]) == 0) { 669 r++; 670 continue; 671 } 672 673 /* Emit any required ZRLs, but not if they can be folded into EOB */ 674 while (r > 15 && k <= EOB) { 675 /* emit any pending EOBRUN and the BE correction bits */ 676 emit_eobrun(entropy); 677 /* Emit ZRL */ 678 emit_symbol(entropy, entropy->ac_tbl_no, 0xF0); 679 r -= 16; 680 /* Emit buffered correction bits that must be associated with ZRL */ 681 emit_buffered_bits(entropy, BR_buffer, BR); 682 BR_buffer = entropy->bit_buffer; /* BE bits are gone now */ 683 BR = 0; 684 } 685 686 /* If the coef was previously nonzero, it only needs a correction bit. 687 * NOTE: a straight translation of the spec's figure G.7 would suggest 688 * that we also need to test r > 15. But if r > 15, we can only get here 689 * if k > EOB, which implies that this coefficient is not 1. 690 */ 691 if (temp > 1) { 692 /* The correction bit is the next bit of the absolute value. */ 693 BR_buffer[BR++] = (char) (temp & 1); 694 continue; 695 } 696 697 /* Emit any pending EOBRUN and the BE correction bits */ 698 emit_eobrun(entropy); 699 700 /* Count/emit Huffman symbol for run length / number of bits */ 701 emit_symbol(entropy, entropy->ac_tbl_no, (r << 4) + 1); 702 703 /* Emit output bit for newly-nonzero coef */ 704 temp = ((*block)[jpeg_natural_order[k]] < 0) ? 0 : 1; 705 emit_bits(entropy, (unsigned int) temp, 1); 706 707 /* Emit buffered correction bits that must be associated with this code */ 708 emit_buffered_bits(entropy, BR_buffer, BR); 709 BR_buffer = entropy->bit_buffer; /* BE bits are gone now */ 710 BR = 0; 711 r = 0; /* reset zero run length */ 712 } 713 714 if (r > 0 || BR > 0) { /* If there are trailing zeroes, */ 715 entropy->EOBRUN++; /* count an EOB */ 716 entropy->BE += BR; /* concat my correction bits to older ones */ 717 /* We force out the EOB if we risk either: 718 * 1. overflow of the EOB counter; 719 * 2. overflow of the correction bit buffer during the next MCU. 720 */ 721 if (entropy->EOBRUN == 0x7FFF || entropy->BE > (MAX_CORR_BITS-DCTSIZE2+1)) 722 emit_eobrun(entropy); 723 } 724 725 cinfo->dest->next_output_byte = entropy->next_output_byte; 726 cinfo->dest->free_in_buffer = entropy->free_in_buffer; 727 728 /* Update restart-interval state too */ 729 if (cinfo->restart_interval) { 730 if (entropy->restarts_to_go == 0) { 731 entropy->restarts_to_go = cinfo->restart_interval; 732 entropy->next_restart_num++; 733 entropy->next_restart_num &= 7; 734 } 735 entropy->restarts_to_go--; 736 } 737 738 return TRUE; 739 } 740 741 742 /* 743 * Finish up at the end of a Huffman-compressed progressive scan. 744 */ 745 746 METHODDEF(void) 747 finish_pass_phuff (j_compress_ptr cinfo) 748 { 749 phuff_entropy_ptr entropy = (phuff_entropy_ptr) cinfo->entropy; 750 751 entropy->next_output_byte = cinfo->dest->next_output_byte; 752 entropy->free_in_buffer = cinfo->dest->free_in_buffer; 753 754 /* Flush out any buffered data */ 755 emit_eobrun(entropy); 756 flush_bits(entropy); 757 758 cinfo->dest->next_output_byte = entropy->next_output_byte; 759 cinfo->dest->free_in_buffer = entropy->free_in_buffer; 760 } 761 762 763 /* 764 * Finish up a statistics-gathering pass and create the new Huffman tables. 765 */ 766 767 METHODDEF(void) 768 finish_pass_gather_phuff (j_compress_ptr cinfo) 769 { 770 phuff_entropy_ptr entropy = (phuff_entropy_ptr) cinfo->entropy; 771 boolean is_DC_band; 772 int ci, tbl; 773 jpeg_component_info *compptr; 774 JHUFF_TBL **htblptr; 775 boolean did[NUM_HUFF_TBLS]; 776 777 /* Flush out buffered data (all we care about is counting the EOB symbol) */ 778 emit_eobrun(entropy); 779 780 is_DC_band = (cinfo->Ss == 0); 781 782 /* It's important not to apply jpeg_gen_optimal_table more than once 783 * per table, because it clobbers the input frequency counts! 784 */ 785 MEMZERO(did, sizeof(did)); 786 787 for (ci = 0; ci < cinfo->comps_in_scan; ci++) { 788 compptr = cinfo->cur_comp_info[ci]; 789 if (is_DC_band) { 790 if (cinfo->Ah != 0) /* DC refinement needs no table */ 791 continue; 792 tbl = compptr->dc_tbl_no; 793 } else { 794 tbl = compptr->ac_tbl_no; 795 } 796 if (! did[tbl]) { 797 if (is_DC_band) 798 htblptr = & cinfo->dc_huff_tbl_ptrs[tbl]; 799 else 800 htblptr = & cinfo->ac_huff_tbl_ptrs[tbl]; 801 if (*htblptr == NULL) 802 *htblptr = jpeg_alloc_huff_table((j_common_ptr) cinfo); 803 jpeg_gen_optimal_table(cinfo, *htblptr, entropy->count_ptrs[tbl]); 804 did[tbl] = TRUE; 805 } 806 } 807 } 808 809 810 /* 811 * Module initialization routine for progressive Huffman entropy encoding. 812 */ 813 814 GLOBAL(void) 815 jinit_phuff_encoder (j_compress_ptr cinfo) 816 { 817 phuff_entropy_ptr entropy; 818 int i; 819 820 entropy = (phuff_entropy_ptr) 821 (*cinfo->mem->alloc_small) ((j_common_ptr) cinfo, JPOOL_IMAGE, 822 sizeof(phuff_entropy_encoder)); 823 cinfo->entropy = (struct jpeg_entropy_encoder *) entropy; 824 entropy->pub.start_pass = start_pass_phuff; 825 826 /* Mark tables unallocated */ 827 for (i = 0; i < NUM_HUFF_TBLS; i++) { 828 entropy->derived_tbls[i] = NULL; 829 entropy->count_ptrs[i] = NULL; 830 } 831 entropy->bit_buffer = NULL; /* needed only in AC refinement scan */ 832 } 833 834 #endif /* C_PROGRESSIVE_SUPPORTED */ 835
