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 INLINE 227 LOCAL(void) 228 emit_bits (phuff_entropy_ptr entropy, unsigned int code, int size) 229 /* Emit some bits, unless we are in gather mode */ 230 { 231 /* This routine is heavily used, so it's worth coding tightly. */ 232 register INT32 put_buffer = (INT32) code; 233 register int put_bits = entropy->put_bits; 234 235 /* if size is 0, caller used an invalid Huffman table entry */ 236 if (size == 0) 237 ERREXIT(entropy->cinfo, JERR_HUFF_MISSING_CODE); 238 239 if (entropy->gather_statistics) 240 return; /* do nothing if we're only getting stats */ 241 242 put_buffer &= (((INT32) 1)<<size) - 1; /* mask off any extra bits in code */ 243 244 put_bits += size; /* new number of bits in buffer */ 245 246 put_buffer <<= 24 - put_bits; /* align incoming bits */ 247 248 put_buffer |= entropy->put_buffer; /* and merge with old buffer contents */ 249 250 while (put_bits >= 8) { 251 int c = (int) ((put_buffer >> 16) & 0xFF); 252 253 emit_byte(entropy, c); 254 if (c == 0xFF) { /* need to stuff a zero byte? */ 255 emit_byte(entropy, 0); 256 } 257 put_buffer <<= 8; 258 put_bits -= 8; 259 } 260 261 entropy->put_buffer = put_buffer; /* update variables */ 262 entropy->put_bits = put_bits; 263 } 264 265 266 LOCAL(void) 267 flush_bits (phuff_entropy_ptr entropy) 268 { 269 emit_bits(entropy, 0x7F, 7); /* fill any partial byte with ones */ 270 entropy->put_buffer = 0; /* and reset bit-buffer to empty */ 271 entropy->put_bits = 0; 272 } 273 274 275 /* 276 * Emit (or just count) a Huffman symbol. 277 */ 278 279 INLINE 280 LOCAL(void) 281 emit_symbol (phuff_entropy_ptr entropy, int tbl_no, int symbol) 282 { 283 if (entropy->gather_statistics) 284 entropy->count_ptrs[tbl_no][symbol]++; 285 else { 286 c_derived_tbl * tbl = entropy->derived_tbls[tbl_no]; 287 emit_bits(entropy, tbl->ehufco[symbol], tbl->ehufsi[symbol]); 288 } 289 } 290 291 292 /* 293 * Emit bits from a correction bit buffer. 294 */ 295 296 LOCAL(void) 297 emit_buffered_bits (phuff_entropy_ptr entropy, char * bufstart, 298 unsigned int nbits) 299 { 300 if (entropy->gather_statistics) 301 return; /* no real work */ 302 303 while (nbits > 0) { 304 emit_bits(entropy, (unsigned int) (*bufstart), 1); 305 bufstart++; 306 nbits--; 307 } 308 } 309 310 311 /* 312 * Emit any pending EOBRUN symbol. 313 */ 314 315 LOCAL(void) 316 emit_eobrun (phuff_entropy_ptr entropy) 317 { 318 register int temp, nbits; 319 320 if (entropy->EOBRUN > 0) { /* if there is any pending EOBRUN */ 321 temp = entropy->EOBRUN; 322 nbits = 0; 323 while ((temp >>= 1)) 324 nbits++; 325 /* safety check: shouldn't happen given limited correction-bit buffer */ 326 if (nbits > 14) 327 ERREXIT(entropy->cinfo, JERR_HUFF_MISSING_CODE); 328 329 emit_symbol(entropy, entropy->ac_tbl_no, nbits << 4); 330 if (nbits) 331 emit_bits(entropy, entropy->EOBRUN, nbits); 332 333 entropy->EOBRUN = 0; 334 335 /* Emit any buffered correction bits */ 336 emit_buffered_bits(entropy, entropy->bit_buffer, entropy->BE); 337 entropy->BE = 0; 338 } 339 } 340 341 342 /* 343 * Emit a restart marker & resynchronize predictions. 344 */ 345 346 LOCAL(void) 347 emit_restart (phuff_entropy_ptr entropy, int restart_num) 348 { 349 int ci; 350 351 emit_eobrun(entropy); 352 353 if (! entropy->gather_statistics) { 354 flush_bits(entropy); 355 emit_byte(entropy, 0xFF); 356 emit_byte(entropy, JPEG_RST0 + restart_num); 357 } 358 359 if (entropy->cinfo->Ss == 0) { 360 /* Re-initialize DC predictions to 0 */ 361 for (ci = 0; ci < entropy->cinfo->comps_in_scan; ci++) 362 entropy->last_dc_val[ci] = 0; 363 } else { 364 /* Re-initialize all AC-related fields to 0 */ 365 entropy->EOBRUN = 0; 366 entropy->BE = 0; 367 } 368 } 369 370 371 /* 372 * MCU encoding for DC initial scan (either spectral selection, 373 * or first pass of successive approximation). 374 */ 375 376 METHODDEF(boolean) 377 encode_mcu_DC_first (j_compress_ptr cinfo, JBLOCKROW *MCU_data) 378 { 379 phuff_entropy_ptr entropy = (phuff_entropy_ptr) cinfo->entropy; 380 register int temp, temp2; 381 register int nbits; 382 int blkn, ci; 383 int Al = cinfo->Al; 384 JBLOCKROW block; 385 jpeg_component_info * compptr; 386 ISHIFT_TEMPS 387 388 entropy->next_output_byte = cinfo->dest->next_output_byte; 389 entropy->free_in_buffer = cinfo->dest->free_in_buffer; 390 391 /* Emit restart marker if needed */ 392 if (cinfo->restart_interval) 393 if (entropy->restarts_to_go == 0) 394 emit_restart(entropy, entropy->next_restart_num); 395 396 /* Encode the MCU data blocks */ 397 for (blkn = 0; blkn < cinfo->blocks_in_MCU; blkn++) { 398 block = MCU_data[blkn]; 399 ci = cinfo->MCU_membership[blkn]; 400 compptr = cinfo->cur_comp_info[ci]; 401 402 /* Compute the DC value after the required point transform by Al. 403 * This is simply an arithmetic right shift. 404 */ 405 temp2 = IRIGHT_SHIFT((int) ((*block)[0]), Al); 406 407 /* DC differences are figured on the point-transformed values. */ 408 temp = temp2 - entropy->last_dc_val[ci]; 409 entropy->last_dc_val[ci] = temp2; 410 411 /* Encode the DC coefficient difference per section G.1.2.1 */ 412 temp2 = temp; 413 if (temp < 0) { 414 temp = -temp; /* temp is abs value of input */ 415 /* For a negative input, want temp2 = bitwise complement of abs(input) */ 416 /* This code assumes we are on a two's complement machine */ 417 temp2--; 418 } 419 420 /* Find the number of bits needed for the magnitude of the coefficient */ 421 nbits = 0; 422 while (temp) { 423 nbits++; 424 temp >>= 1; 425 } 426 /* Check for out-of-range coefficient values. 427 * Since we're encoding a difference, the range limit is twice as much. 428 */ 429 if (nbits > MAX_COEF_BITS+1) 430 ERREXIT(cinfo, JERR_BAD_DCT_COEF); 431 432 /* Count/emit the Huffman-coded symbol for the number of bits */ 433 emit_symbol(entropy, compptr->dc_tbl_no, nbits); 434 435 /* Emit that number of bits of the value, if positive, */ 436 /* or the complement of its magnitude, if negative. */ 437 if (nbits) /* emit_bits rejects calls with size 0 */ 438 emit_bits(entropy, (unsigned int) temp2, nbits); 439 } 440 441 cinfo->dest->next_output_byte = entropy->next_output_byte; 442 cinfo->dest->free_in_buffer = entropy->free_in_buffer; 443 444 /* Update restart-interval state too */ 445 if (cinfo->restart_interval) { 446 if (entropy->restarts_to_go == 0) { 447 entropy->restarts_to_go = cinfo->restart_interval; 448 entropy->next_restart_num++; 449 entropy->next_restart_num &= 7; 450 } 451 entropy->restarts_to_go--; 452 } 453 454 return TRUE; 455 } 456 457 458 /* 459 * MCU encoding for AC initial scan (either spectral selection, 460 * or first pass of successive approximation). 461 */ 462 463 METHODDEF(boolean) 464 encode_mcu_AC_first (j_compress_ptr cinfo, JBLOCKROW *MCU_data) 465 { 466 phuff_entropy_ptr entropy = (phuff_entropy_ptr) cinfo->entropy; 467 register int temp, temp2; 468 register int nbits; 469 register int r, k; 470 int Se = cinfo->Se; 471 int Al = cinfo->Al; 472 JBLOCKROW block; 473 474 entropy->next_output_byte = cinfo->dest->next_output_byte; 475 entropy->free_in_buffer = cinfo->dest->free_in_buffer; 476 477 /* Emit restart marker if needed */ 478 if (cinfo->restart_interval) 479 if (entropy->restarts_to_go == 0) 480 emit_restart(entropy, entropy->next_restart_num); 481 482 /* Encode the MCU data block */ 483 block = MCU_data[0]; 484 485 /* Encode the AC coefficients per section G.1.2.2, fig. G.3 */ 486 487 r = 0; /* r = run length of zeros */ 488 489 for (k = cinfo->Ss; k <= Se; k++) { 490 if ((temp = (*block)[jpeg_natural_order[k]]) == 0) { 491 r++; 492 continue; 493 } 494 /* We must apply the point transform by Al. For AC coefficients this 495 * is an integer division with rounding towards 0. To do this portably 496 * in C, we shift after obtaining the absolute value; so the code is 497 * interwoven with finding the abs value (temp) and output bits (temp2). 498 */ 499 if (temp < 0) { 500 temp = -temp; /* temp is abs value of input */ 501 temp >>= Al; /* apply the point transform */ 502 /* For a negative coef, want temp2 = bitwise complement of abs(coef) */ 503 temp2 = ~temp; 504 } else { 505 temp >>= Al; /* apply the point transform */ 506 temp2 = temp; 507 } 508 /* Watch out for case that nonzero coef is zero after point transform */ 509 if (temp == 0) { 510 r++; 511 continue; 512 } 513 514 /* Emit any pending EOBRUN */ 515 if (entropy->EOBRUN > 0) 516 emit_eobrun(entropy); 517 /* if run length > 15, must emit special run-length-16 codes (0xF0) */ 518 while (r > 15) { 519 emit_symbol(entropy, entropy->ac_tbl_no, 0xF0); 520 r -= 16; 521 } 522 523 /* Find the number of bits needed for the magnitude of the coefficient */ 524 nbits = 1; /* there must be at least one 1 bit */ 525 while ((temp >>= 1)) 526 nbits++; 527 /* Check for out-of-range coefficient values */ 528 if (nbits > MAX_COEF_BITS) 529 ERREXIT(cinfo, JERR_BAD_DCT_COEF); 530 531 /* Count/emit Huffman symbol for run length / number of bits */ 532 emit_symbol(entropy, entropy->ac_tbl_no, (r << 4) + nbits); 533 534 /* Emit that number of bits of the value, if positive, */ 535 /* or the complement of its magnitude, if negative. */ 536 emit_bits(entropy, (unsigned int) temp2, nbits); 537 538 r = 0; /* reset zero run length */ 539 } 540 541 if (r > 0) { /* If there are trailing zeroes, */ 542 entropy->EOBRUN++; /* count an EOB */ 543 if (entropy->EOBRUN == 0x7FFF) 544 emit_eobrun(entropy); /* force it out to avoid overflow */ 545 } 546 547 cinfo->dest->next_output_byte = entropy->next_output_byte; 548 cinfo->dest->free_in_buffer = entropy->free_in_buffer; 549 550 /* Update restart-interval state too */ 551 if (cinfo->restart_interval) { 552 if (entropy->restarts_to_go == 0) { 553 entropy->restarts_to_go = cinfo->restart_interval; 554 entropy->next_restart_num++; 555 entropy->next_restart_num &= 7; 556 } 557 entropy->restarts_to_go--; 558 } 559 560 return TRUE; 561 } 562 563 564 /* 565 * MCU encoding for DC successive approximation refinement scan. 566 * Note: we assume such scans can be multi-component, although the spec 567 * is not very clear on the point. 568 */ 569 570 METHODDEF(boolean) 571 encode_mcu_DC_refine (j_compress_ptr cinfo, JBLOCKROW *MCU_data) 572 { 573 phuff_entropy_ptr entropy = (phuff_entropy_ptr) cinfo->entropy; 574 register int temp; 575 int blkn; 576 int Al = cinfo->Al; 577 JBLOCKROW block; 578 579 entropy->next_output_byte = cinfo->dest->next_output_byte; 580 entropy->free_in_buffer = cinfo->dest->free_in_buffer; 581 582 /* Emit restart marker if needed */ 583 if (cinfo->restart_interval) 584 if (entropy->restarts_to_go == 0) 585 emit_restart(entropy, entropy->next_restart_num); 586 587 /* Encode the MCU data blocks */ 588 for (blkn = 0; blkn < cinfo->blocks_in_MCU; blkn++) { 589 block = MCU_data[blkn]; 590 591 /* We simply emit the Al'th bit of the DC coefficient value. */ 592 temp = (*block)[0]; 593 emit_bits(entropy, (unsigned int) (temp >> Al), 1); 594 } 595 596 cinfo->dest->next_output_byte = entropy->next_output_byte; 597 cinfo->dest->free_in_buffer = entropy->free_in_buffer; 598 599 /* Update restart-interval state too */ 600 if (cinfo->restart_interval) { 601 if (entropy->restarts_to_go == 0) { 602 entropy->restarts_to_go = cinfo->restart_interval; 603 entropy->next_restart_num++; 604 entropy->next_restart_num &= 7; 605 } 606 entropy->restarts_to_go--; 607 } 608 609 return TRUE; 610 } 611 612 613 /* 614 * MCU encoding for AC successive approximation refinement scan. 615 */ 616 617 METHODDEF(boolean) 618 encode_mcu_AC_refine (j_compress_ptr cinfo, JBLOCKROW *MCU_data) 619 { 620 phuff_entropy_ptr entropy = (phuff_entropy_ptr) cinfo->entropy; 621 register int temp; 622 register int r, k; 623 int EOB; 624 char *BR_buffer; 625 unsigned int BR; 626 int Se = cinfo->Se; 627 int Al = cinfo->Al; 628 JBLOCKROW block; 629 int absvalues[DCTSIZE2]; 630 631 entropy->next_output_byte = cinfo->dest->next_output_byte; 632 entropy->free_in_buffer = cinfo->dest->free_in_buffer; 633 634 /* Emit restart marker if needed */ 635 if (cinfo->restart_interval) 636 if (entropy->restarts_to_go == 0) 637 emit_restart(entropy, entropy->next_restart_num); 638 639 /* Encode the MCU data block */ 640 block = MCU_data[0]; 641 642 /* It is convenient to make a pre-pass to determine the transformed 643 * coefficients' absolute values and the EOB position. 644 */ 645 EOB = 0; 646 for (k = cinfo->Ss; k <= Se; k++) { 647 temp = (*block)[jpeg_natural_order[k]]; 648 /* We must apply the point transform by Al. For AC coefficients this 649 * is an integer division with rounding towards 0. To do this portably 650 * in C, we shift after obtaining the absolute value. 651 */ 652 if (temp < 0) 653 temp = -temp; /* temp is abs value of input */ 654 temp >>= Al; /* apply the point transform */ 655 absvalues[k] = temp; /* save abs value for main pass */ 656 if (temp == 1) 657 EOB = k; /* EOB = index of last newly-nonzero coef */ 658 } 659 660 /* Encode the AC coefficients per section G.1.2.3, fig. G.7 */ 661 662 r = 0; /* r = run length of zeros */ 663 BR = 0; /* BR = count of buffered bits added now */ 664 BR_buffer = entropy->bit_buffer + entropy->BE; /* Append bits to buffer */ 665 666 for (k = cinfo->Ss; k <= Se; k++) { 667 if ((temp = absvalues[k]) == 0) { 668 r++; 669 continue; 670 } 671 672 /* Emit any required ZRLs, but not if they can be folded into EOB */ 673 while (r > 15 && k <= EOB) { 674 /* emit any pending EOBRUN and the BE correction bits */ 675 emit_eobrun(entropy); 676 /* Emit ZRL */ 677 emit_symbol(entropy, entropy->ac_tbl_no, 0xF0); 678 r -= 16; 679 /* Emit buffered correction bits that must be associated with ZRL */ 680 emit_buffered_bits(entropy, BR_buffer, BR); 681 BR_buffer = entropy->bit_buffer; /* BE bits are gone now */ 682 BR = 0; 683 } 684 685 /* If the coef was previously nonzero, it only needs a correction bit. 686 * NOTE: a straight translation of the spec's figure G.7 would suggest 687 * that we also need to test r > 15. But if r > 15, we can only get here 688 * if k > EOB, which implies that this coefficient is not 1. 689 */ 690 if (temp > 1) { 691 /* The correction bit is the next bit of the absolute value. */ 692 BR_buffer[BR++] = (char) (temp & 1); 693 continue; 694 } 695 696 /* Emit any pending EOBRUN and the BE correction bits */ 697 emit_eobrun(entropy); 698 699 /* Count/emit Huffman symbol for run length / number of bits */ 700 emit_symbol(entropy, entropy->ac_tbl_no, (r << 4) + 1); 701 702 /* Emit output bit for newly-nonzero coef */ 703 temp = ((*block)[jpeg_natural_order[k]] < 0) ? 0 : 1; 704 emit_bits(entropy, (unsigned int) temp, 1); 705 706 /* Emit buffered correction bits that must be associated with this code */ 707 emit_buffered_bits(entropy, BR_buffer, BR); 708 BR_buffer = entropy->bit_buffer; /* BE bits are gone now */ 709 BR = 0; 710 r = 0; /* reset zero run length */ 711 } 712 713 if (r > 0 || BR > 0) { /* If there are trailing zeroes, */ 714 entropy->EOBRUN++; /* count an EOB */ 715 entropy->BE += BR; /* concat my correction bits to older ones */ 716 /* We force out the EOB if we risk either: 717 * 1. overflow of the EOB counter; 718 * 2. overflow of the correction bit buffer during the next MCU. 719 */ 720 if (entropy->EOBRUN == 0x7FFF || entropy->BE > (MAX_CORR_BITS-DCTSIZE2+1)) 721 emit_eobrun(entropy); 722 } 723 724 cinfo->dest->next_output_byte = entropy->next_output_byte; 725 cinfo->dest->free_in_buffer = entropy->free_in_buffer; 726 727 /* Update restart-interval state too */ 728 if (cinfo->restart_interval) { 729 if (entropy->restarts_to_go == 0) { 730 entropy->restarts_to_go = cinfo->restart_interval; 731 entropy->next_restart_num++; 732 entropy->next_restart_num &= 7; 733 } 734 entropy->restarts_to_go--; 735 } 736 737 return TRUE; 738 } 739 740 741 /* 742 * Finish up at the end of a Huffman-compressed progressive scan. 743 */ 744 745 METHODDEF(void) 746 finish_pass_phuff (j_compress_ptr cinfo) 747 { 748 phuff_entropy_ptr entropy = (phuff_entropy_ptr) cinfo->entropy; 749 750 entropy->next_output_byte = cinfo->dest->next_output_byte; 751 entropy->free_in_buffer = cinfo->dest->free_in_buffer; 752 753 /* Flush out any buffered data */ 754 emit_eobrun(entropy); 755 flush_bits(entropy); 756 757 cinfo->dest->next_output_byte = entropy->next_output_byte; 758 cinfo->dest->free_in_buffer = entropy->free_in_buffer; 759 } 760 761 762 /* 763 * Finish up a statistics-gathering pass and create the new Huffman tables. 764 */ 765 766 METHODDEF(void) 767 finish_pass_gather_phuff (j_compress_ptr cinfo) 768 { 769 phuff_entropy_ptr entropy = (phuff_entropy_ptr) cinfo->entropy; 770 boolean is_DC_band; 771 int ci, tbl; 772 jpeg_component_info * compptr; 773 JHUFF_TBL **htblptr; 774 boolean did[NUM_HUFF_TBLS]; 775 776 /* Flush out buffered data (all we care about is counting the EOB symbol) */ 777 emit_eobrun(entropy); 778 779 is_DC_band = (cinfo->Ss == 0); 780 781 /* It's important not to apply jpeg_gen_optimal_table more than once 782 * per table, because it clobbers the input frequency counts! 783 */ 784 MEMZERO(did, SIZEOF(did)); 785 786 for (ci = 0; ci < cinfo->comps_in_scan; ci++) { 787 compptr = cinfo->cur_comp_info[ci]; 788 if (is_DC_band) { 789 if (cinfo->Ah != 0) /* DC refinement needs no table */ 790 continue; 791 tbl = compptr->dc_tbl_no; 792 } else { 793 tbl = compptr->ac_tbl_no; 794 } 795 if (! did[tbl]) { 796 if (is_DC_band) 797 htblptr = & cinfo->dc_huff_tbl_ptrs[tbl]; 798 else 799 htblptr = & cinfo->ac_huff_tbl_ptrs[tbl]; 800 if (*htblptr == NULL) 801 *htblptr = jpeg_alloc_huff_table((j_common_ptr) cinfo); 802 jpeg_gen_optimal_table(cinfo, *htblptr, entropy->count_ptrs[tbl]); 803 did[tbl] = TRUE; 804 } 805 } 806 } 807 808 809 /* 810 * Module initialization routine for progressive Huffman entropy encoding. 811 */ 812 813 GLOBAL(void) 814 jinit_phuff_encoder (j_compress_ptr cinfo) 815 { 816 phuff_entropy_ptr entropy; 817 int i; 818 819 entropy = (phuff_entropy_ptr) 820 (*cinfo->mem->alloc_small) ((j_common_ptr) cinfo, JPOOL_IMAGE, 821 SIZEOF(phuff_entropy_encoder)); 822 cinfo->entropy = (struct jpeg_entropy_encoder *) entropy; 823 entropy->pub.start_pass = start_pass_phuff; 824 825 /* Mark tables unallocated */ 826 for (i = 0; i < NUM_HUFF_TBLS; i++) { 827 entropy->derived_tbls[i] = NULL; 828 entropy->count_ptrs[i] = NULL; 829 } 830 entropy->bit_buffer = NULL; /* needed only in AC refinement scan */ 831 } 832 833 #endif /* C_PROGRESSIVE_SUPPORTED */ 834
