1 /* 2 * jcphuff.c 3 * 4 * Copyright (C) 1995-1997, Thomas G. Lane. 5 * This file is part of the Independent JPEG Group's software. 6 * For conditions of distribution and use, see the accompanying README file. 7 * 8 * This file contains Huffman entropy encoding routines for progressive JPEG. 9 * 10 * We do not support output suspension in this module, since the library 11 * currently does not allow multiple-scan files to be written with output 12 * suspension. 13 */ 14 15 #define JPEG_INTERNALS 16 #include "jinclude.h" 17 #include "jpeglib.h" 18 #include "jchuff.h" /* Declarations shared with jchuff.c */ 19 20 #ifdef C_PROGRESSIVE_SUPPORTED 21 22 /* Expanded entropy encoder object for progressive Huffman encoding. */ 23 24 typedef struct { 25 struct jpeg_entropy_encoder pub; /* public fields */ 26 27 /* Mode flag: TRUE for optimization, FALSE for actual data output */ 28 boolean gather_statistics; 29 30 /* Bit-level coding status. 31 * next_output_byte/free_in_buffer are local copies of cinfo->dest fields. 32 */ 33 JOCTET * next_output_byte; /* => next byte to write in buffer */ 34 size_t free_in_buffer; /* # of byte spaces remaining in buffer */ 35 INT32 put_buffer; /* current bit-accumulation buffer */ 36 int put_bits; /* # of bits now in it */ 37 j_compress_ptr cinfo; /* link to cinfo (needed for dump_buffer) */ 38 39 /* Coding status for DC components */ 40 int last_dc_val[MAX_COMPS_IN_SCAN]; /* last DC coef for each component */ 41 42 /* Coding status for AC components */ 43 int ac_tbl_no; /* the table number of the single component */ 44 unsigned int EOBRUN; /* run length of EOBs */ 45 unsigned int BE; /* # of buffered correction bits before MCU */ 46 char * bit_buffer; /* buffer for correction bits (1 per char) */ 47 /* packing correction bits tightly would save some space but cost time... */ 48 49 unsigned int restarts_to_go; /* MCUs left in this restart interval */ 50 int next_restart_num; /* next restart number to write (0-7) */ 51 52 /* Pointers to derived tables (these workspaces have image lifespan). 53 * Since any one scan codes only DC or only AC, we only need one set 54 * of tables, not one for DC and one for AC. 55 */ 56 c_derived_tbl * derived_tbls[NUM_HUFF_TBLS]; 57 58 /* Statistics tables for optimization; again, one set is enough */ 59 long * count_ptrs[NUM_HUFF_TBLS]; 60 } phuff_entropy_encoder; 61 62 typedef phuff_entropy_encoder * phuff_entropy_ptr; 63 64 /* MAX_CORR_BITS is the number of bits the AC refinement correction-bit 65 * buffer can hold. Larger sizes may slightly improve compression, but 66 * 1000 is already well into the realm of overkill. 67 * The minimum safe size is 64 bits. 68 */ 69 70 #define MAX_CORR_BITS 1000 /* Max # of correction bits I can buffer */ 71 72 /* IRIGHT_SHIFT is like RIGHT_SHIFT, but works on int rather than INT32. 73 * We assume that int right shift is unsigned if INT32 right shift is, 74 * which should be safe. 75 */ 76 77 #ifdef RIGHT_SHIFT_IS_UNSIGNED 78 #define ISHIFT_TEMPS int ishift_temp; 79 #define IRIGHT_SHIFT(x,shft) \ 80 ((ishift_temp = (x)) < 0 ? \ 81 (ishift_temp >> (shft)) | ((~0) << (16-(shft))) : \ 82 (ishift_temp >> (shft))) 83 #else 84 #define ISHIFT_TEMPS 85 #define IRIGHT_SHIFT(x,shft) ((x) >> (shft)) 86 #endif 87 88 /* Forward declarations */ 89 METHODDEF(boolean) encode_mcu_DC_first JPP((j_compress_ptr cinfo, 90 JBLOCKROW *MCU_data)); 91 METHODDEF(boolean) encode_mcu_AC_first JPP((j_compress_ptr cinfo, 92 JBLOCKROW *MCU_data)); 93 METHODDEF(boolean) encode_mcu_DC_refine JPP((j_compress_ptr cinfo, 94 JBLOCKROW *MCU_data)); 95 METHODDEF(boolean) encode_mcu_AC_refine JPP((j_compress_ptr cinfo, 96 JBLOCKROW *MCU_data)); 97 METHODDEF(void) finish_pass_phuff JPP((j_compress_ptr cinfo)); 98 METHODDEF(void) finish_pass_gather_phuff JPP((j_compress_ptr cinfo)); 99 100 101 /* 102 * Initialize for a Huffman-compressed scan using progressive JPEG. 103 */ 104 105 METHODDEF(void) 106 start_pass_phuff (j_compress_ptr cinfo, boolean gather_statistics) 107 { 108 phuff_entropy_ptr entropy = (phuff_entropy_ptr) cinfo->entropy; 109 boolean is_DC_band; 110 int ci, tbl; 111 jpeg_component_info * compptr; 112 113 entropy->cinfo = cinfo; 114 entropy->gather_statistics = gather_statistics; 115 116 is_DC_band = (cinfo->Ss == 0); 117 118 /* We assume jcmaster.c already validated the scan parameters. */ 119 120 /* Select execution routines */ 121 if (cinfo->Ah == 0) { 122 if (is_DC_band) 123 entropy->pub.encode_mcu = encode_mcu_DC_first; 124 else 125 entropy->pub.encode_mcu = encode_mcu_AC_first; 126 } else { 127 if (is_DC_band) 128 entropy->pub.encode_mcu = encode_mcu_DC_refine; 129 else { 130 entropy->pub.encode_mcu = encode_mcu_AC_refine; 131 /* AC refinement needs a correction bit buffer */ 132 if (entropy->bit_buffer == NULL) 133 entropy->bit_buffer = (char *) 134 (*cinfo->mem->alloc_small) ((j_common_ptr) cinfo, JPOOL_IMAGE, 135 MAX_CORR_BITS * SIZEOF(char)); 136 } 137 } 138 if (gather_statistics) 139 entropy->pub.finish_pass = finish_pass_gather_phuff; 140 else 141 entropy->pub.finish_pass = finish_pass_phuff; 142 143 /* Only DC coefficients may be interleaved, so cinfo->comps_in_scan = 1 144 * for AC coefficients. 145 */ 146 for (ci = 0; ci < cinfo->comps_in_scan; ci++) { 147 compptr = cinfo->cur_comp_info[ci]; 148 /* Initialize DC predictions to 0 */ 149 entropy->last_dc_val[ci] = 0; 150 /* Get table index */ 151 if (is_DC_band) { 152 if (cinfo->Ah != 0) /* DC refinement needs no table */ 153 continue; 154 tbl = compptr->dc_tbl_no; 155 } else { 156 entropy->ac_tbl_no = tbl = compptr->ac_tbl_no; 157 } 158 if (gather_statistics) { 159 /* Check for invalid table index */ 160 /* (make_c_derived_tbl does this in the other path) */ 161 if (tbl < 0 || tbl >= NUM_HUFF_TBLS) 162 ERREXIT1(cinfo, JERR_NO_HUFF_TABLE, tbl); 163 /* Allocate and zero the statistics tables */ 164 /* Note that jpeg_gen_optimal_table expects 257 entries in each table! */ 165 if (entropy->count_ptrs[tbl] == NULL) 166 entropy->count_ptrs[tbl] = (long *) 167 (*cinfo->mem->alloc_small) ((j_common_ptr) cinfo, JPOOL_IMAGE, 168 257 * SIZEOF(long)); 169 MEMZERO(entropy->count_ptrs[tbl], 257 * SIZEOF(long)); 170 } else { 171 /* Compute derived values for Huffman table */ 172 /* We may do this more than once for a table, but it's not expensive */ 173 jpeg_make_c_derived_tbl(cinfo, is_DC_band, tbl, 174 & entropy->derived_tbls[tbl]); 175 } 176 } 177 178 /* Initialize AC stuff */ 179 entropy->EOBRUN = 0; 180 entropy->BE = 0; 181 182 /* Initialize bit buffer to empty */ 183 entropy->put_buffer = 0; 184 entropy->put_bits = 0; 185 186 /* Initialize restart stuff */ 187 entropy->restarts_to_go = cinfo->restart_interval; 188 entropy->next_restart_num = 0; 189 } 190 191 192 /* Outputting bytes to the file. 193 * NB: these must be called only when actually outputting, 194 * that is, entropy->gather_statistics == FALSE. 195 */ 196 197 /* Emit a byte */ 198 #define emit_byte(entropy,val) \ 199 { *(entropy)->next_output_byte++ = (JOCTET) (val); \ 200 if (--(entropy)->free_in_buffer == 0) \ 201 dump_buffer(entropy); } 202 203 204 LOCAL(void) 205 dump_buffer (phuff_entropy_ptr entropy) 206 /* Empty the output buffer; we do not support suspension in this module. */ 207 { 208 struct jpeg_destination_mgr * dest = entropy->cinfo->dest; 209 210 if (! (*dest->empty_output_buffer) (entropy->cinfo)) 211 ERREXIT(entropy->cinfo, JERR_CANT_SUSPEND); 212 /* After a successful buffer dump, must reset buffer pointers */ 213 entropy->next_output_byte = dest->next_output_byte; 214 entropy->free_in_buffer = dest->free_in_buffer; 215 } 216 217 218 /* Outputting bits to the file */ 219 220 /* Only the right 24 bits of put_buffer are used; the valid bits are 221 * left-justified in this part. At most 16 bits can be passed to emit_bits 222 * in one call, and we never retain more than 7 bits in put_buffer 223 * between calls, so 24 bits are sufficient. 224 */ 225 226 LOCAL(void) 227 emit_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 } 263 264 265 LOCAL(void) 266 flush_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 */ 277 278 LOCAL(void) 279 emit_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 */ 293 294 LOCAL(void) 295 emit_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 */ 312 313 LOCAL(void) 314 emit_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++; 323 /* safety check: shouldn't happen given limited correction-bit buffer */ 324 if (nbits > 14) 325 ERREXIT(entropy->cinfo, JERR_HUFF_MISSING_CODE); 326 327 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 */ 343 344 LOCAL(void) 345 emit_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 */ 373 374 METHODDEF(boolean) 375 encode_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 } 424 /* 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); 429 430 /* 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 */ 460 461 METHODDEF(boolean) 462 encode_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++; 525 /* Check for out-of-range coefficient values */ 526 if (nbits > MAX_COEF_BITS) 527 ERREXIT(cinfo, JERR_BAD_DCT_COEF); 528 529 /* 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 */ 567 568 METHODDEF(boolean) 569 encode_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 */ 614 615 METHODDEF(boolean) 616 encode_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 */ 742 743 METHODDEF(void) 744 finish_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 */ 763 764 METHODDEF(void) 765 finish_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 */ 810 811 GLOBAL(void) 812 jinit_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 */ 832
