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| 1 /* | |
| 2 * jchuff.c | |
| 3 * | |
| 4 * Copyright (C) 1991-1997, 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. | |
| 9 * | |
| 10 * Much of the complexity here has to do with supporting output suspension. | |
| 11 * If the data destination module demands suspension, we want to be able to | |
| 12 * back up to the start of the current MCU. To do this, we copy state | |
| 13 * variables into local working storage, and update them back to the | |
| 14 * permanent JPEG objects only upon successful completion of an MCU. | |
| 15 */ | |
| 16 | |
| 17 #define JPEG_INTERNALS | |
| 18 #include "jinclude.h" | |
| 19 #include "jpeglib.h" | |
| 20 #include "jchuff.h" /* Declarations shared with jcphuff.c */ | |
| 21 | |
| 22 | |
| 23 /* Expanded entropy encoder object for Huffman encoding. | |
| 24 * | |
| 25 * The savable_state subrecord contains fields that change within an MCU, | |
| 26 * but must not be updated permanently until we complete the MCU. | |
| 27 */ | |
| 28 | |
| 29 typedef struct { | |
| 30 INT32 put_buffer; /* current bit-accumulation buffer */ | |
| 31 int put_bits; /* # of bits now in it */ | |
| 32 int last_dc_val[MAX_COMPS_IN_SCAN]; /* last DC coef for each component */ | |
| 33 } savable_state; | |
| 34 | |
| 35 /* This macro is to work around compilers with missing or broken | |
| 36 * structure assignment. You'll need to fix this code if you have | |
| 37 * such a compiler and you change MAX_COMPS_IN_SCAN. | |
| 38 */ | |
| 39 | |
| 40 #ifndef NO_STRUCT_ASSIGN | |
| 41 #define ASSIGN_STATE(dest,src) ((dest) = (src)) | |
| 42 #else | |
| 43 #if MAX_COMPS_IN_SCAN == 4 | |
| 44 #define ASSIGN_STATE(dest,src) \ | |
| 45 ((dest).put_buffer = (src).put_buffer, \ | |
| 46 (dest).put_bits = (src).put_bits, \ | |
| 47 (dest).last_dc_val[0] = (src).last_dc_val[0], \ | |
| 48 (dest).last_dc_val[1] = (src).last_dc_val[1], \ | |
| 49 (dest).last_dc_val[2] = (src).last_dc_val[2], \ | |
| 50 (dest).last_dc_val[3] = (src).last_dc_val[3]) | |
| 51 #endif | |
| 52 #endif | |
| 53 | |
| 54 | |
| 55 typedef struct { | |
| 56 struct jpeg_entropy_encoder pub; /* public fields */ | |
| 57 | |
| 58 savable_state saved; /* Bit buffer & DC state at start of MCU */ | |
| 59 | |
| 60 /* These fields are NOT loaded into local working state. */ | |
| 61 unsigned int restarts_to_go; /* MCUs left in this restart interval */ | |
| 62 int next_restart_num; /* next restart number to write (0-7) */ | |
| 63 | |
| 64 /* Pointers to derived tables (these workspaces have image lifespan) */ | |
| 65 c_derived_tbl * dc_derived_tbls[NUM_HUFF_TBLS]; | |
| 66 c_derived_tbl * ac_derived_tbls[NUM_HUFF_TBLS]; | |
| 67 | |
| 68 #ifdef ENTROPY_OPT_SUPPORTED /* Statistics tables for optimization */ | |
| 69 long * dc_count_ptrs[NUM_HUFF_TBLS]; | |
| 70 long * ac_count_ptrs[NUM_HUFF_TBLS]; | |
| 71 #endif | |
| 72 } huff_entropy_encoder; | |
| 73 | |
| 74 typedef huff_entropy_encoder * huff_entropy_ptr; | |
| 75 | |
| 76 /* Working state while writing an MCU. | |
| 77 * This struct contains all the fields that are needed by subroutines. | |
| 78 */ | |
| 79 | |
| 80 typedef struct { | |
| 81 JOCTET * next_output_byte; /* => next byte to write in buffer */ | |
| 82 size_t free_in_buffer; /* # of byte spaces remaining in buffer */ | |
| 83 savable_state cur; /* Current bit buffer & DC state */ | |
| 84 j_compress_ptr cinfo; /* dump_buffer needs access to this */ | |
| 85 } working_state; | |
| 86 | |
| 87 | |
| 88 /* Forward declarations */ | |
| 89 METHODDEF(boolean) encode_mcu_huff JPP((j_compress_ptr cinfo, | |
| 90 JBLOCKROW *MCU_data)); | |
| 91 METHODDEF(void) finish_pass_huff JPP((j_compress_ptr cinfo)); | |
| 92 #ifdef ENTROPY_OPT_SUPPORTED | |
| 93 METHODDEF(boolean) encode_mcu_gather JPP((j_compress_ptr cinfo, | |
| 94 JBLOCKROW *MCU_data)); | |
| 95 METHODDEF(void) finish_pass_gather JPP((j_compress_ptr cinfo)); | |
| 96 #endif | |
| 97 | |
| 98 | |
| 99 /* | |
| 100 * Initialize for a Huffman-compressed scan. | |
| 101 * If gather_statistics is TRUE, we do not output anything during the scan, | |
| 102 * just count the Huffman symbols used and generate Huffman code tables. | |
| 103 */ | |
| 104 | |
| 105 METHODDEF(void) | |
| 106 start_pass_huff (j_compress_ptr cinfo, boolean gather_statistics) | |
| 107 { | |
| 108 huff_entropy_ptr entropy = (huff_entropy_ptr) cinfo->entropy; | |
| 109 int ci, dctbl, actbl; | |
| 110 jpeg_component_info * compptr; | |
| 111 | |
| 112 if (gather_statistics) { | |
| 113 #ifdef ENTROPY_OPT_SUPPORTED | |
| 114 entropy->pub.encode_mcu = encode_mcu_gather; | |
| 115 entropy->pub.finish_pass = finish_pass_gather; | |
| 116 #else | |
| 117 ERREXIT(cinfo, JERR_NOT_COMPILED); | |
| 118 #endif | |
| 119 } else { | |
| 120 entropy->pub.encode_mcu = encode_mcu_huff; | |
| 121 entropy->pub.finish_pass = finish_pass_huff; | |
| 122 } | |
| 123 | |
| 124 for (ci = 0; ci < cinfo->comps_in_scan; ci++) { | |
| 125 compptr = cinfo->cur_comp_info[ci]; | |
| 126 dctbl = compptr->dc_tbl_no; | |
| 127 actbl = compptr->ac_tbl_no; | |
| 128 if (gather_statistics) { | |
| 129 #ifdef ENTROPY_OPT_SUPPORTED | |
| 130 /* Check for invalid table indexes */ | |
| 131 /* (make_c_derived_tbl does this in the other path) */ | |
| 132 if (dctbl < 0 || dctbl >= NUM_HUFF_TBLS) | |
| 133 ERREXIT1(cinfo, JERR_NO_HUFF_TABLE, dctbl); | |
| 134 if (actbl < 0 || actbl >= NUM_HUFF_TBLS) | |
| 135 ERREXIT1(cinfo, JERR_NO_HUFF_TABLE, actbl); | |
| 136 /* Allocate and zero the statistics tables */ | |
| 137 /* Note that jpeg_gen_optimal_table expects 257 entries in each table! */ | |
| 138 if (entropy->dc_count_ptrs[dctbl] == NULL) | |
| 139 entropy->dc_count_ptrs[dctbl] = (long *) | |
| 140 (*cinfo->mem->alloc_small) ((j_common_ptr) cinfo, JPOOL_IMAGE, | |
| 141 257 * SIZEOF(long)); | |
| 142 MEMZERO(entropy->dc_count_ptrs[dctbl], 257 * SIZEOF(long)); | |
| 143 if (entropy->ac_count_ptrs[actbl] == NULL) | |
| 144 entropy->ac_count_ptrs[actbl] = (long *) | |
| 145 (*cinfo->mem->alloc_small) ((j_common_ptr) cinfo, JPOOL_IMAGE, | |
| 146 257 * SIZEOF(long)); | |
| 147 MEMZERO(entropy->ac_count_ptrs[actbl], 257 * SIZEOF(long)); | |
| 148 #endif | |
| 149 } else { | |
| 150 /* Compute derived values for Huffman tables */ | |
| 151 /* We may do this more than once for a table, but it's not expensive */ | |
| 152 jpeg_make_c_derived_tbl(cinfo, TRUE, dctbl, | |
| 153 & entropy->dc_derived_tbls[dctbl]); | |
| 154 jpeg_make_c_derived_tbl(cinfo, FALSE, actbl, | |
| 155 & entropy->ac_derived_tbls[actbl]); | |
| 156 } | |
| 157 /* Initialize DC predictions to 0 */ | |
| 158 entropy->saved.last_dc_val[ci] = 0; | |
| 159 } | |
| 160 | |
| 161 /* Initialize bit buffer to empty */ | |
| 162 entropy->saved.put_buffer = 0; | |
| 163 entropy->saved.put_bits = 0; | |
| 164 | |
| 165 /* Initialize restart stuff */ | |
| 166 entropy->restarts_to_go = cinfo->restart_interval; | |
| 167 entropy->next_restart_num = 0; | |
| 168 } | |
| 169 | |
| 170 | |
| 171 /* | |
| 172 * Compute the derived values for a Huffman table. | |
| 173 * This routine also performs some validation checks on the table. | |
| 174 * | |
| 175 * Note this is also used by jcphuff.c. | |
| 176 */ | |
| 177 | |
| 178 GLOBAL(void) | |
| 179 jpeg_make_c_derived_tbl (j_compress_ptr cinfo, boolean isDC, int tblno, | |
| 180 c_derived_tbl ** pdtbl) | |
| 181 { | |
| 182 JHUFF_TBL *htbl; | |
| 183 c_derived_tbl *dtbl; | |
| 184 int p, i, l, lastp, si, maxsymbol; | |
| 185 char huffsize[257]; | |
| 186 unsigned int huffcode[257]; | |
| 187 unsigned int code; | |
| 188 | |
| 189 /* Note that huffsize[] and huffcode[] are filled in code-length order, | |
| 190 * paralleling the order of the symbols themselves in htbl->huffval[]. | |
| 191 */ | |
| 192 | |
| 193 /* Find the input Huffman table */ | |
| 194 if (tblno < 0 || tblno >= NUM_HUFF_TBLS) | |
| 195 ERREXIT1(cinfo, JERR_NO_HUFF_TABLE, tblno); | |
| 196 htbl = | |
| 197 isDC ? cinfo->dc_huff_tbl_ptrs[tblno] : cinfo->ac_huff_tbl_ptrs[tblno]; | |
| 198 if (htbl == NULL) | |
| 199 ERREXIT1(cinfo, JERR_NO_HUFF_TABLE, tblno); | |
| 200 | |
| 201 /* Allocate a workspace if we haven't already done so. */ | |
| 202 if (*pdtbl == NULL) | |
| 203 *pdtbl = (c_derived_tbl *) | |
| 204 (*cinfo->mem->alloc_small) ((j_common_ptr) cinfo, JPOOL_IMAGE, | |
| 205 SIZEOF(c_derived_tbl)); | |
| 206 dtbl = *pdtbl; | |
| 207 | |
| 208 /* Figure C.1: make table of Huffman code length for each symbol */ | |
| 209 | |
| 210 p = 0; | |
| 211 for (l = 1; l <= 16; l++) { | |
| 212 i = (int) htbl->bits[l]; | |
| 213 if (i < 0 || p + i > 256) /* protect against table overrun */ | |
| 214 ERREXIT(cinfo, JERR_BAD_HUFF_TABLE); | |
| 215 while (i--) | |
| 216 huffsize[p++] = (char) l; | |
| 217 } | |
| 218 huffsize[p] = 0; | |
| 219 lastp = p; | |
| 220 | |
| 221 /* Figure C.2: generate the codes themselves */ | |
| 222 /* We also validate that the counts represent a legal Huffman code tree. */ | |
| 223 | |
| 224 code = 0; | |
| 225 si = huffsize[0]; | |
| 226 p = 0; | |
| 227 while (huffsize[p]) { | |
| 228 while (((int) huffsize[p]) == si) { | |
| 229 huffcode[p++] = code; | |
| 230 code++; | |
| 231 } | |
| 232 /* code is now 1 more than the last code used for codelength si; but | |
| 233 * it must still fit in si bits, since no code is allowed to be all ones. | |
| 234 */ | |
| 235 if (((INT32) code) >= (((INT32) 1) << si)) | |
| 236 ERREXIT(cinfo, JERR_BAD_HUFF_TABLE); | |
| 237 code <<= 1; | |
| 238 si++; | |
| 239 } | |
| 240 | |
| 241 /* Figure C.3: generate encoding tables */ | |
| 242 /* These are code and size indexed by symbol value */ | |
| 243 | |
| 244 /* Set all codeless symbols to have code length 0; | |
| 245 * this lets us detect duplicate VAL entries here, and later | |
| 246 * allows emit_bits to detect any attempt to emit such symbols. | |
| 247 */ | |
| 248 MEMZERO(dtbl->ehufsi, SIZEOF(dtbl->ehufsi)); | |
| 249 | |
| 250 /* This is also a convenient place to check for out-of-range | |
| 251 * and duplicated VAL entries. We allow 0..255 for AC symbols | |
| 252 * but only 0..15 for DC. (We could constrain them further | |
| 253 * based on data depth and mode, but this seems enough.) | |
| 254 */ | |
| 255 maxsymbol = isDC ? 15 : 255; | |
| 256 | |
| 257 for (p = 0; p < lastp; p++) { | |
| 258 i = htbl->huffval[p]; | |
| 259 if (i < 0 || i > maxsymbol || dtbl->ehufsi[i]) | |
| 260 ERREXIT(cinfo, JERR_BAD_HUFF_TABLE); | |
| 261 dtbl->ehufco[i] = huffcode[p]; | |
| 262 dtbl->ehufsi[i] = huffsize[p]; | |
| 263 } | |
| 264 } | |
| 265 | |
| 266 | |
| 267 /* Outputting bytes to the file */ | |
| 268 | |
| 269 /* Emit a byte, taking 'action' if must suspend. */ | |
| 270 #define emit_byte(state,val,action) \ | |
| 271 { *(state)->next_output_byte++ = (JOCTET) (val); \ | |
| 272 if (--(state)->free_in_buffer == 0) \ | |
| 273 if (! dump_buffer(state)) \ | |
| 274 { action; } } | |
| 275 | |
| 276 | |
| 277 LOCAL(boolean) | |
| 278 dump_buffer (working_state * state) | |
| 279 /* Empty the output buffer; return TRUE if successful, FALSE if must suspend */ | |
| 280 { | |
| 281 struct jpeg_destination_mgr * dest = state->cinfo->dest; | |
| 282 | |
| 283 if (! (*dest->empty_output_buffer) (state->cinfo)) | |
| 284 return FALSE; | |
| 285 /* After a successful buffer dump, must reset buffer pointers */ | |
| 286 state->next_output_byte = dest->next_output_byte; | |
| 287 state->free_in_buffer = dest->free_in_buffer; | |
| 288 return TRUE; | |
| 289 } | |
| 290 | |
| 291 | |
| 292 /* Outputting bits to the file */ | |
| 293 | |
| 294 /* Only the right 24 bits of put_buffer are used; the valid bits are | |
| 295 * left-justified in this part. At most 16 bits can be passed to emit_bits | |
| 296 * in one call, and we never retain more than 7 bits in put_buffer | |
| 297 * between calls, so 24 bits are sufficient. | |
| 298 */ | |
| 299 | |
| 300 INLINE | |
| 301 LOCAL(boolean) | |
| 302 emit_bits (working_state * state, unsigned int code, int size) | |
| 303 /* Emit some bits; return TRUE if successful, FALSE if must suspend */ | |
| 304 { | |
| 305 /* This routine is heavily used, so it's worth coding tightly. */ | |
| 306 register INT32 put_buffer = (INT32) code; | |
| 307 register int put_bits = state->cur.put_bits; | |
| 308 | |
| 309 /* if size is 0, caller used an invalid Huffman table entry */ | |
| 310 if (size == 0) | |
| 311 ERREXIT(state->cinfo, JERR_HUFF_MISSING_CODE); | |
| 312 | |
| 313 put_buffer &= (((INT32) 1)<<size) - 1; /* mask off any extra bits in code */ | |
| 314 | |
| 315 put_bits += size; /* new number of bits in buffer */ | |
| 316 | |
| 317 put_buffer <<= 24 - put_bits; /* align incoming bits */ | |
| 318 | |
| 319 put_buffer |= state->cur.put_buffer; /* and merge with old buffer contents */ | |
| 320 | |
| 321 while (put_bits >= 8) { | |
| 322 int c = (int) ((put_buffer >> 16) & 0xFF); | |
| 323 | |
| 324 emit_byte(state, c, return FALSE); | |
| 325 if (c == 0xFF) { /* need to stuff a zero byte? */ | |
| 326 emit_byte(state, 0, return FALSE); | |
| 327 } | |
| 328 put_buffer <<= 8; | |
| 329 put_bits -= 8; | |
| 330 } | |
| 331 | |
| 332 state->cur.put_buffer = put_buffer; /* update state variables */ | |
| 333 state->cur.put_bits = put_bits; | |
| 334 | |
| 335 return TRUE; | |
| 336 } | |
| 337 | |
| 338 | |
| 339 LOCAL(boolean) | |
| 340 flush_bits (working_state * state) | |
| 341 { | |
| 342 if (! emit_bits(state, 0x7F, 7)) /* fill any partial byte with ones */ | |
| 343 return FALSE; | |
| 344 state->cur.put_buffer = 0; /* and reset bit-buffer to empty */ | |
| 345 state->cur.put_bits = 0; | |
| 346 return TRUE; | |
| 347 } | |
| 348 | |
| 349 | |
| 350 /* Encode a single block's worth of coefficients */ | |
| 351 | |
| 352 LOCAL(boolean) | |
| 353 encode_one_block (working_state * state, JCOEFPTR block, int last_dc_val, | |
| 354 c_derived_tbl *dctbl, c_derived_tbl *actbl) | |
| 355 { | |
| 356 register int temp, temp2; | |
| 357 register int nbits; | |
| 358 register int k, r, i; | |
| 359 | |
| 360 /* Encode the DC coefficient difference per section F.1.2.1 */ | |
| 361 | |
| 362 temp = temp2 = block[0] - last_dc_val; | |
| 363 | |
| 364 if (temp < 0) { | |
| 365 temp = -temp; /* temp is abs value of input */ | |
| 366 /* For a negative input, want temp2 = bitwise complement of abs(input) */ | |
| 367 /* This code assumes we are on a two's complement machine */ | |
| 368 temp2--; | |
| 369 } | |
| 370 | |
| 371 /* Find the number of bits needed for the magnitude of the coefficient */ | |
| 372 nbits = 0; | |
| 373 while (temp) { | |
| 374 nbits++; | |
| 375 temp >>= 1; | |
| 376 } | |
| 377 /* Check for out-of-range coefficient values. | |
| 378 * Since we're encoding a difference, the range limit is twice as much. | |
| 379 */ | |
| 380 if (nbits > MAX_COEF_BITS+1) | |
| 381 ERREXIT(state->cinfo, JERR_BAD_DCT_COEF); | |
| 382 | |
| 383 /* Emit the Huffman-coded symbol for the number of bits */ | |
| 384 if (! emit_bits(state, dctbl->ehufco[nbits], dctbl->ehufsi[nbits])) | |
| 385 return FALSE; | |
| 386 | |
| 387 /* Emit that number of bits of the value, if positive, */ | |
| 388 /* or the complement of its magnitude, if negative. */ | |
| 389 if (nbits) /* emit_bits rejects calls with size 0 */ | |
| 390 if (! emit_bits(state, (unsigned int) temp2, nbits)) | |
| 391 return FALSE; | |
| 392 | |
| 393 /* Encode the AC coefficients per section F.1.2.2 */ | |
| 394 | |
| 395 r = 0; /* r = run length of zeros */ | |
| 396 | |
| 397 for (k = 1; k < DCTSIZE2; k++) { | |
| 398 if ((temp = block[jpeg_natural_order[k]]) == 0) { | |
| 399 r++; | |
| 400 } else { | |
| 401 /* if run length > 15, must emit special run-length-16 codes (0xF0) */ | |
| 402 while (r > 15) { | |
| 403 if (! emit_bits(state, actbl->ehufco[0xF0], actbl->ehufsi[0xF0])) | |
| 404 return FALSE; | |
| 405 r -= 16; | |
| 406 } | |
| 407 | |
| 408 temp2 = temp; | |
| 409 if (temp < 0) { | |
| 410 temp = -temp; /* temp is abs value of input */ | |
| 411 /* This code assumes we are on a two's complement machine */ | |
| 412 temp2--; | |
| 413 } | |
| 414 | |
| 415 /* Find the number of bits needed for the magnitude of the coefficient */ | |
| 416 nbits = 1; /* there must be at least one 1 bit */ | |
| 417 while ((temp >>= 1)) | |
| 418 nbits++; | |
| 419 /* Check for out-of-range coefficient values */ | |
| 420 if (nbits > MAX_COEF_BITS) | |
| 421 ERREXIT(state->cinfo, JERR_BAD_DCT_COEF); | |
| 422 | |
| 423 /* Emit Huffman symbol for run length / number of bits */ | |
| 424 i = (r << 4) + nbits; | |
| 425 if (! emit_bits(state, actbl->ehufco[i], actbl->ehufsi[i])) | |
| 426 return FALSE; | |
| 427 | |
| 428 /* Emit that number of bits of the value, if positive, */ | |
| 429 /* or the complement of its magnitude, if negative. */ | |
| 430 if (! emit_bits(state, (unsigned int) temp2, nbits)) | |
| 431 return FALSE; | |
| 432 | |
| 433 r = 0; | |
| 434 } | |
| 435 } | |
| 436 | |
| 437 /* If the last coef(s) were zero, emit an end-of-block code */ | |
| 438 if (r > 0) | |
| 439 if (! emit_bits(state, actbl->ehufco[0], actbl->ehufsi[0])) | |
| 440 return FALSE; | |
| 441 | |
| 442 return TRUE; | |
| 443 } | |
| 444 | |
| 445 | |
| 446 /* | |
| 447 * Emit a restart marker & resynchronize predictions. | |
| 448 */ | |
| 449 | |
| 450 LOCAL(boolean) | |
| 451 emit_restart (working_state * state, int restart_num) | |
| 452 { | |
| 453 int ci; | |
| 454 | |
| 455 if (! flush_bits(state)) | |
| 456 return FALSE; | |
| 457 | |
| 458 emit_byte(state, 0xFF, return FALSE); | |
| 459 emit_byte(state, JPEG_RST0 + restart_num, return FALSE); | |
| 460 | |
| 461 /* Re-initialize DC predictions to 0 */ | |
| 462 for (ci = 0; ci < state->cinfo->comps_in_scan; ci++) | |
| 463 state->cur.last_dc_val[ci] = 0; | |
| 464 | |
| 465 /* The restart counter is not updated until we successfully write the MCU. */ | |
| 466 | |
| 467 return TRUE; | |
| 468 } | |
| 469 | |
| 470 | |
| 471 /* | |
| 472 * Encode and output one MCU's worth of Huffman-compressed coefficients. | |
| 473 */ | |
| 474 | |
| 475 METHODDEF(boolean) | |
| 476 encode_mcu_huff (j_compress_ptr cinfo, JBLOCKROW *MCU_data) | |
| 477 { | |
| 478 huff_entropy_ptr entropy = (huff_entropy_ptr) cinfo->entropy; | |
| 479 working_state state; | |
| 480 int blkn, ci; | |
| 481 jpeg_component_info * compptr; | |
| 482 | |
| 483 /* Load up working state */ | |
| 484 state.next_output_byte = cinfo->dest->next_output_byte; | |
| 485 state.free_in_buffer = cinfo->dest->free_in_buffer; | |
| 486 ASSIGN_STATE(state.cur, entropy->saved); | |
| 487 state.cinfo = cinfo; | |
| 488 | |
| 489 /* Emit restart marker if needed */ | |
| 490 if (cinfo->restart_interval) { | |
| 491 if (entropy->restarts_to_go == 0) | |
| 492 if (! emit_restart(&state, entropy->next_restart_num)) | |
| 493 return FALSE; | |
| 494 } | |
| 495 | |
| 496 /* Encode the MCU data blocks */ | |
| 497 for (blkn = 0; blkn < cinfo->blocks_in_MCU; blkn++) { | |
| 498 ci = cinfo->MCU_membership[blkn]; | |
| 499 compptr = cinfo->cur_comp_info[ci]; | |
| 500 if (! encode_one_block(&state, | |
| 501 MCU_data[blkn][0], state.cur.last_dc_val[ci], | |
| 502 entropy->dc_derived_tbls[compptr->dc_tbl_no], | |
| 503 entropy->ac_derived_tbls[compptr->ac_tbl_no])) | |
| 504 return FALSE; | |
| 505 /* Update last_dc_val */ | |
| 506 state.cur.last_dc_val[ci] = MCU_data[blkn][0][0]; | |
| 507 } | |
| 508 | |
| 509 /* Completed MCU, so update state */ | |
| 510 cinfo->dest->next_output_byte = state.next_output_byte; | |
| 511 cinfo->dest->free_in_buffer = state.free_in_buffer; | |
| 512 ASSIGN_STATE(entropy->saved, state.cur); | |
| 513 | |
| 514 /* Update restart-interval state too */ | |
| 515 if (cinfo->restart_interval) { | |
| 516 if (entropy->restarts_to_go == 0) { | |
| 517 entropy->restarts_to_go = cinfo->restart_interval; | |
| 518 entropy->next_restart_num++; | |
| 519 entropy->next_restart_num &= 7; | |
| 520 } | |
| 521 entropy->restarts_to_go--; | |
| 522 } | |
| 523 | |
| 524 return TRUE; | |
| 525 } | |
| 526 | |
| 527 | |
| 528 /* | |
| 529 * Finish up at the end of a Huffman-compressed scan. | |
| 530 */ | |
| 531 | |
| 532 METHODDEF(void) | |
| 533 finish_pass_huff (j_compress_ptr cinfo) | |
| 534 { | |
| 535 huff_entropy_ptr entropy = (huff_entropy_ptr) cinfo->entropy; | |
| 536 working_state state; | |
| 537 | |
| 538 /* Load up working state ... flush_bits needs it */ | |
| 539 state.next_output_byte = cinfo->dest->next_output_byte; | |
| 540 state.free_in_buffer = cinfo->dest->free_in_buffer; | |
| 541 ASSIGN_STATE(state.cur, entropy->saved); | |
| 542 state.cinfo = cinfo; | |
| 543 | |
| 544 /* Flush out the last data */ | |
| 545 if (! flush_bits(&state)) | |
| 546 ERREXIT(cinfo, JERR_CANT_SUSPEND); | |
| 547 | |
| 548 /* Update state */ | |
| 549 cinfo->dest->next_output_byte = state.next_output_byte; | |
| 550 cinfo->dest->free_in_buffer = state.free_in_buffer; | |
| 551 ASSIGN_STATE(entropy->saved, state.cur); | |
| 552 } | |
| 553 | |
| 554 | |
| 555 /* | |
| 556 * Huffman coding optimization. | |
| 557 * | |
| 558 * We first scan the supplied data and count the number of uses of each symbol | |
| 559 * that is to be Huffman-coded. (This process MUST agree with the code above.) | |
| 560 * Then we build a Huffman coding tree for the observed counts. | |
| 561 * Symbols which are not needed at all for the particular image are not | |
| 562 * assigned any code, which saves space in the DHT marker as well as in | |
| 563 * the compressed data. | |
| 564 */ | |
| 565 | |
| 566 #ifdef ENTROPY_OPT_SUPPORTED | |
| 567 | |
| 568 | |
| 569 /* Process a single block's worth of coefficients */ | |
| 570 | |
| 571 LOCAL(void) | |
| 572 htest_one_block (j_compress_ptr cinfo, JCOEFPTR block, int last_dc_val, | |
| 573 long dc_counts[], long ac_counts[]) | |
| 574 { | |
| 575 register int temp; | |
| 576 register int nbits; | |
| 577 register int k, r; | |
| 578 | |
| 579 /* Encode the DC coefficient difference per section F.1.2.1 */ | |
| 580 | |
| 581 temp = block[0] - last_dc_val; | |
| 582 if (temp < 0) | |
| 583 temp = -temp; | |
| 584 | |
| 585 /* Find the number of bits needed for the magnitude of the coefficient */ | |
| 586 nbits = 0; | |
| 587 while (temp) { | |
| 588 nbits++; | |
| 589 temp >>= 1; | |
| 590 } | |
| 591 /* Check for out-of-range coefficient values. | |
| 592 * Since we're encoding a difference, the range limit is twice as much. | |
| 593 */ | |
| 594 if (nbits > MAX_COEF_BITS+1) | |
| 595 ERREXIT(cinfo, JERR_BAD_DCT_COEF); | |
| 596 | |
| 597 /* Count the Huffman symbol for the number of bits */ | |
| 598 dc_counts[nbits]++; | |
| 599 | |
| 600 /* Encode the AC coefficients per section F.1.2.2 */ | |
| 601 | |
| 602 r = 0; /* r = run length of zeros */ | |
| 603 | |
| 604 for (k = 1; k < DCTSIZE2; k++) { | |
| 605 if ((temp = block[jpeg_natural_order[k]]) == 0) { | |
| 606 r++; | |
| 607 } else { | |
| 608 /* if run length > 15, must emit special run-length-16 codes (0xF0) */ | |
| 609 while (r > 15) { | |
| 610 ac_counts[0xF0]++; | |
| 611 r -= 16; | |
| 612 } | |
| 613 | |
| 614 /* Find the number of bits needed for the magnitude of the coefficient */ | |
| 615 if (temp < 0) | |
| 616 temp = -temp; | |
| 617 | |
| 618 /* Find the number of bits needed for the magnitude of the coefficient */ | |
| 619 nbits = 1; /* there must be at least one 1 bit */ | |
| 620 while ((temp >>= 1)) | |
| 621 nbits++; | |
| 622 /* Check for out-of-range coefficient values */ | |
| 623 if (nbits > MAX_COEF_BITS) | |
| 624 ERREXIT(cinfo, JERR_BAD_DCT_COEF); | |
| 625 | |
| 626 /* Count Huffman symbol for run length / number of bits */ | |
| 627 ac_counts[(r << 4) + nbits]++; | |
| 628 | |
| 629 r = 0; | |
| 630 } | |
| 631 } | |
| 632 | |
| 633 /* If the last coef(s) were zero, emit an end-of-block code */ | |
| 634 if (r > 0) | |
| 635 ac_counts[0]++; | |
| 636 } | |
| 637 | |
| 638 | |
| 639 /* | |
| 640 * Trial-encode one MCU's worth of Huffman-compressed coefficients. | |
| 641 * No data is actually output, so no suspension return is possible. | |
| 642 */ | |
| 643 | |
| 644 METHODDEF(boolean) | |
| 645 encode_mcu_gather (j_compress_ptr cinfo, JBLOCKROW *MCU_data) | |
| 646 { | |
| 647 huff_entropy_ptr entropy = (huff_entropy_ptr) cinfo->entropy; | |
| 648 int blkn, ci; | |
| 649 jpeg_component_info * compptr; | |
| 650 | |
| 651 /* Take care of restart intervals if needed */ | |
| 652 if (cinfo->restart_interval) { | |
| 653 if (entropy->restarts_to_go == 0) { | |
| 654 /* Re-initialize DC predictions to 0 */ | |
| 655 for (ci = 0; ci < cinfo->comps_in_scan; ci++) | |
| 656 entropy->saved.last_dc_val[ci] = 0; | |
| 657 /* Update restart state */ | |
| 658 entropy->restarts_to_go = cinfo->restart_interval; | |
| 659 } | |
| 660 entropy->restarts_to_go--; | |
| 661 } | |
| 662 | |
| 663 for (blkn = 0; blkn < cinfo->blocks_in_MCU; blkn++) { | |
| 664 ci = cinfo->MCU_membership[blkn]; | |
| 665 compptr = cinfo->cur_comp_info[ci]; | |
| 666 htest_one_block(cinfo, MCU_data[blkn][0], entropy->saved.last_dc_val[ci], | |
| 667 entropy->dc_count_ptrs[compptr->dc_tbl_no], | |
| 668 entropy->ac_count_ptrs[compptr->ac_tbl_no]); | |
| 669 entropy->saved.last_dc_val[ci] = MCU_data[blkn][0][0]; | |
| 670 } | |
| 671 | |
| 672 return TRUE; | |
| 673 } | |
| 674 | |
| 675 | |
| 676 /* | |
| 677 * Generate the best Huffman code table for the given counts, fill htbl. | |
| 678 * Note this is also used by jcphuff.c. | |
| 679 * | |
| 680 * The JPEG standard requires that no symbol be assigned a codeword of all | |
| 681 * one bits (so that padding bits added at the end of a compressed segment | |
| 682 * can't look like a valid code). Because of the canonical ordering of | |
| 683 * codewords, this just means that there must be an unused slot in the | |
| 684 * longest codeword length category. Section K.2 of the JPEG spec suggests | |
| 685 * reserving such a slot by pretending that symbol 256 is a valid symbol | |
| 686 * with count 1. In theory that's not optimal; giving it count zero but | |
| 687 * including it in the symbol set anyway should give a better Huffman code. | |
| 688 * But the theoretically better code actually seems to come out worse in | |
| 689 * practice, because it produces more all-ones bytes (which incur stuffed | |
| 690 * zero bytes in the final file). In any case the difference is tiny. | |
| 691 * | |
| 692 * The JPEG standard requires Huffman codes to be no more than 16 bits long. | |
| 693 * If some symbols have a very small but nonzero probability, the Huffman tree | |
| 694 * must be adjusted to meet the code length restriction. We currently use | |
| 695 * the adjustment method suggested in JPEG section K.2. This method is *not* | |
| 696 * optimal; it may not choose the best possible limited-length code. But | |
| 697 * typically only very-low-frequency symbols will be given less-than-optimal | |
| 698 * lengths, so the code is almost optimal. Experimental comparisons against | |
| 699 * an optimal limited-length-code algorithm indicate that the difference is | |
| 700 * microscopic --- usually less than a hundredth of a percent of total size. | |
| 701 * So the extra complexity of an optimal algorithm doesn't seem worthwhile. | |
| 702 */ | |
| 703 | |
| 704 GLOBAL(void) | |
| 705 jpeg_gen_optimal_table (j_compress_ptr cinfo, JHUFF_TBL * htbl, long freq[]) | |
| 706 { | |
| 707 #define MAX_CLEN 32 /* assumed maximum initial code length */ | |
| 708 UINT8 bits[MAX_CLEN+1]; /* bits[k] = # of symbols with code length k */ | |
| 709 int codesize[257]; /* codesize[k] = code length of symbol k */ | |
| 710 int others[257]; /* next symbol in current branch of tree */ | |
| 711 int c1, c2; | |
| 712 int p, i, j; | |
| 713 long v; | |
| 714 | |
| 715 /* This algorithm is explained in section K.2 of the JPEG standard */ | |
| 716 | |
| 717 MEMZERO(bits, SIZEOF(bits)); | |
| 718 MEMZERO(codesize, SIZEOF(codesize)); | |
| 719 for (i = 0; i < 257; i++) | |
| 720 others[i] = -1; /* init links to empty */ | |
| 721 | |
| 722 freq[256] = 1; /* make sure 256 has a nonzero count */ | |
| 723 /* Including the pseudo-symbol 256 in the Huffman procedure guarantees | |
| 724 * that no real symbol is given code-value of all ones, because 256 | |
| 725 * will be placed last in the largest codeword category. | |
| 726 */ | |
| 727 | |
| 728 /* Huffman's basic algorithm to assign optimal code lengths to symbols */ | |
| 729 | |
| 730 for (;;) { | |
| 731 /* Find the smallest nonzero frequency, set c1 = its symbol */ | |
| 732 /* In case of ties, take the larger symbol number */ | |
| 733 c1 = -1; | |
| 734 v = 1000000000L; | |
| 735 for (i = 0; i <= 256; i++) { | |
| 736 if (freq[i] && freq[i] <= v) { | |
| 737 v = freq[i]; | |
| 738 c1 = i; | |
| 739 } | |
| 740 } | |
| 741 | |
| 742 /* Find the next smallest nonzero frequency, set c2 = its symbol */ | |
| 743 /* In case of ties, take the larger symbol number */ | |
| 744 c2 = -1; | |
| 745 v = 1000000000L; | |
| 746 for (i = 0; i <= 256; i++) { | |
| 747 if (freq[i] && freq[i] <= v && i != c1) { | |
| 748 v = freq[i]; | |
| 749 c2 = i; | |
| 750 } | |
| 751 } | |
| 752 | |
| 753 /* Done if we've merged everything into one frequency */ | |
| 754 if (c2 < 0) | |
| 755 break; | |
| 756 | |
| 757 /* Else merge the two counts/trees */ | |
| 758 freq[c1] += freq[c2]; | |
| 759 freq[c2] = 0; | |
| 760 | |
| 761 /* Increment the codesize of everything in c1's tree branch */ | |
| 762 codesize[c1]++; | |
| 763 while (others[c1] >= 0) { | |
| 764 c1 = others[c1]; | |
| 765 codesize[c1]++; | |
| 766 } | |
| 767 | |
| 768 others[c1] = c2; /* chain c2 onto c1's tree branch */ | |
| 769 | |
| 770 /* Increment the codesize of everything in c2's tree branch */ | |
| 771 codesize[c2]++; | |
| 772 while (others[c2] >= 0) { | |
| 773 c2 = others[c2]; | |
| 774 codesize[c2]++; | |
| 775 } | |
| 776 } | |
| 777 | |
| 778 /* Now count the number of symbols of each code length */ | |
| 779 for (i = 0; i <= 256; i++) { | |
| 780 if (codesize[i]) { | |
| 781 /* The JPEG standard seems to think that this can't happen, */ | |
| 782 /* but I'm paranoid... */ | |
| 783 if (codesize[i] > MAX_CLEN) | |
| 784 ERREXIT(cinfo, JERR_HUFF_CLEN_OVERFLOW); | |
| 785 | |
| 786 bits[codesize[i]]++; | |
| 787 } | |
| 788 } | |
| 789 | |
| 790 /* JPEG doesn't allow symbols with code lengths over 16 bits, so if the pure | |
| 791 * Huffman procedure assigned any such lengths, we must adjust the coding. | |
| 792 * Here is what the JPEG spec says about how this next bit works: | |
| 793 * Since symbols are paired for the longest Huffman code, the symbols are | |
| 794 * removed from this length category two at a time. The prefix for the pair | |
| 795 * (which is one bit shorter) is allocated to one of the pair; then, | |
| 796 * skipping the BITS entry for that prefix length, a code word from the next | |
| 797 * shortest nonzero BITS entry is converted into a prefix for two code words | |
| 798 * one bit longer. | |
| 799 */ | |
| 800 | |
| 801 for (i = MAX_CLEN; i > 16; i--) { | |
| 802 while (bits[i] > 0) { | |
| 803 j = i - 2; /* find length of new prefix to be used */ | |
| 804 while (bits[j] == 0) | |
| 805 j--; | |
| 806 | |
| 807 bits[i] -= 2; /* remove two symbols */ | |
| 808 bits[i-1]++; /* one goes in this length */ | |
| 809 bits[j+1] += 2; /* two new symbols in this length */ | |
| 810 bits[j]--; /* symbol of this length is now a prefix */ | |
| 811 } | |
| 812 } | |
| 813 | |
| 814 /* Remove the count for the pseudo-symbol 256 from the largest codelength */ | |
| 815 while (bits[i] == 0) /* find largest codelength still in use */ | |
| 816 i--; | |
| 817 bits[i]--; | |
| 818 | |
| 819 /* Return final symbol counts (only for lengths 0..16) */ | |
| 820 MEMCOPY(htbl->bits, bits, SIZEOF(htbl->bits)); | |
| 821 | |
| 822 /* Return a list of the symbols sorted by code length */ | |
| 823 /* It's not real clear to me why we don't need to consider the codelength | |
| 824 * changes made above, but the JPEG spec seems to think this works. | |
| 825 */ | |
| 826 p = 0; | |
| 827 for (i = 1; i <= MAX_CLEN; i++) { | |
| 828 for (j = 0; j <= 255; j++) { | |
| 829 if (codesize[j] == i) { | |
| 830 htbl->huffval[p] = (UINT8) j; | |
| 831 p++; | |
| 832 } | |
| 833 } | |
| 834 } | |
| 835 | |
| 836 /* Set sent_table FALSE so updated table will be written to JPEG file. */ | |
| 837 htbl->sent_table = FALSE; | |
| 838 } | |
| 839 | |
| 840 | |
| 841 /* | |
| 842 * Finish up a statistics-gathering pass and create the new Huffman tables. | |
| 843 */ | |
| 844 | |
| 845 METHODDEF(void) | |
| 846 finish_pass_gather (j_compress_ptr cinfo) | |
| 847 { | |
| 848 huff_entropy_ptr entropy = (huff_entropy_ptr) cinfo->entropy; | |
| 849 int ci, dctbl, actbl; | |
| 850 jpeg_component_info * compptr; | |
| 851 JHUFF_TBL **htblptr; | |
| 852 boolean did_dc[NUM_HUFF_TBLS]; | |
| 853 boolean did_ac[NUM_HUFF_TBLS]; | |
| 854 | |
| 855 /* It's important not to apply jpeg_gen_optimal_table more than once | |
| 856 * per table, because it clobbers the input frequency counts! | |
| 857 */ | |
| 858 MEMZERO(did_dc, SIZEOF(did_dc)); | |
| 859 MEMZERO(did_ac, SIZEOF(did_ac)); | |
| 860 | |
| 861 for (ci = 0; ci < cinfo->comps_in_scan; ci++) { | |
| 862 compptr = cinfo->cur_comp_info[ci]; | |
| 863 dctbl = compptr->dc_tbl_no; | |
| 864 actbl = compptr->ac_tbl_no; | |
| 865 if (! did_dc[dctbl]) { | |
| 866 htblptr = & cinfo->dc_huff_tbl_ptrs[dctbl]; | |
| 867 if (*htblptr == NULL) | |
| 868 *htblptr = jpeg_alloc_huff_table((j_common_ptr) cinfo); | |
| 869 jpeg_gen_optimal_table(cinfo, *htblptr, entropy->dc_count_ptrs[dctbl]); | |
| 870 did_dc[dctbl] = TRUE; | |
| 871 } | |
| 872 if (! did_ac[actbl]) { | |
| 873 htblptr = & cinfo->ac_huff_tbl_ptrs[actbl]; | |
| 874 if (*htblptr == NULL) | |
| 875 *htblptr = jpeg_alloc_huff_table((j_common_ptr) cinfo); | |
| 876 jpeg_gen_optimal_table(cinfo, *htblptr, entropy->ac_count_ptrs[actbl]); | |
| 877 did_ac[actbl] = TRUE; | |
| 878 } | |
| 879 } | |
| 880 } | |
| 881 | |
| 882 | |
| 883 #endif /* ENTROPY_OPT_SUPPORTED */ | |
| 884 | |
| 885 | |
| 886 /* | |
| 887 * Module initialization routine for Huffman entropy encoding. | |
| 888 */ | |
| 889 | |
| 890 GLOBAL(void) | |
| 891 jinit_huff_encoder (j_compress_ptr cinfo) | |
| 892 { | |
| 893 huff_entropy_ptr entropy; | |
| 894 int i; | |
| 895 | |
| 896 entropy = (huff_entropy_ptr) | |
| 897 (*cinfo->mem->alloc_small) ((j_common_ptr) cinfo, JPOOL_IMAGE, | |
| 898 SIZEOF(huff_entropy_encoder)); | |
| 899 cinfo->entropy = (struct jpeg_entropy_encoder *) entropy; | |
| 900 entropy->pub.start_pass = start_pass_huff; | |
| 901 | |
| 902 /* Mark tables unallocated */ | |
| 903 for (i = 0; i < NUM_HUFF_TBLS; i++) { | |
| 904 entropy->dc_derived_tbls[i] = entropy->ac_derived_tbls[i] = NULL; | |
| 905 #ifdef ENTROPY_OPT_SUPPORTED | |
| 906 entropy->dc_count_ptrs[i] = entropy->ac_count_ptrs[i] = NULL; | |
| 907 #endif | |
| 908 } | |
| 909 } | |
| OLD | NEW |
|---|
Chromium Code Reviews
Issue 1705523002:
Remove libjpeg and libjpeg_turbo. (Closed)
Base URL: https://github.com/domokit/mojo.git@master