jcparam.c (19497B)
1 /* 2 * jcparam.c 3 * 4 * This file was part of the Independent JPEG Group's software: 5 * Copyright (C) 1991-1998, Thomas G. Lane. 6 * Modified 2003-2008 by Guido Vollbeding. 7 * Lossless JPEG Modifications: 8 * Copyright (C) 1999, Ken Murchison. 9 * libjpeg-turbo Modifications: 10 * Copyright (C) 2009-2011, 2018, 2023, D. R. Commander. 11 * For conditions of distribution and use, see the accompanying README.ijg 12 * file. 13 * 14 * This file contains optional default-setting code for the JPEG compressor. 15 * Applications do not have to use this file, but those that don't use it 16 * must know a lot more about the innards of the JPEG code. 17 */ 18 19 #define JPEG_INTERNALS 20 #include "jinclude.h" 21 #include "jpeglib.h" 22 #include "jstdhuff.c" 23 24 25 /* 26 * Quantization table setup routines 27 */ 28 29 GLOBAL(void) 30 jpeg_add_quant_table(j_compress_ptr cinfo, int which_tbl, 31 const unsigned int *basic_table, int scale_factor, 32 boolean force_baseline) 33 /* Define a quantization table equal to the basic_table times 34 * a scale factor (given as a percentage). 35 * If force_baseline is TRUE, the computed quantization table entries 36 * are limited to 1..255 for JPEG baseline compatibility. 37 */ 38 { 39 JQUANT_TBL **qtblptr; 40 int i; 41 long temp; 42 43 /* Safety check to ensure start_compress not called yet. */ 44 if (cinfo->global_state != CSTATE_START) 45 ERREXIT1(cinfo, JERR_BAD_STATE, cinfo->global_state); 46 47 if (which_tbl < 0 || which_tbl >= NUM_QUANT_TBLS) 48 ERREXIT1(cinfo, JERR_DQT_INDEX, which_tbl); 49 50 qtblptr = &cinfo->quant_tbl_ptrs[which_tbl]; 51 52 if (*qtblptr == NULL) 53 *qtblptr = jpeg_alloc_quant_table((j_common_ptr)cinfo); 54 55 for (i = 0; i < DCTSIZE2; i++) { 56 temp = ((long)basic_table[i] * scale_factor + 50L) / 100L; 57 /* limit the values to the valid range */ 58 if (temp <= 0L) temp = 1L; 59 if (temp > 32767L) temp = 32767L; /* max quantizer needed for 12 bits */ 60 if (force_baseline && temp > 255L) 61 temp = 255L; /* limit to baseline range if requested */ 62 (*qtblptr)->quantval[i] = (UINT16)temp; 63 } 64 65 /* Initialize sent_table FALSE so table will be written to JPEG file. */ 66 (*qtblptr)->sent_table = FALSE; 67 } 68 69 70 /* These are the sample quantization tables given in Annex K (Clause K.1) of 71 * Recommendation ITU-T T.81 (1992) | ISO/IEC 10918-1:1994. 72 * The spec says that the values given produce "good" quality, and 73 * when divided by 2, "very good" quality. 74 */ 75 static const unsigned int std_luminance_quant_tbl[DCTSIZE2] = { 76 16, 11, 10, 16, 24, 40, 51, 61, 77 12, 12, 14, 19, 26, 58, 60, 55, 78 14, 13, 16, 24, 40, 57, 69, 56, 79 14, 17, 22, 29, 51, 87, 80, 62, 80 18, 22, 37, 56, 68, 109, 103, 77, 81 24, 35, 55, 64, 81, 104, 113, 92, 82 49, 64, 78, 87, 103, 121, 120, 101, 83 72, 92, 95, 98, 112, 100, 103, 99 84 }; 85 static const unsigned int std_chrominance_quant_tbl[DCTSIZE2] = { 86 17, 18, 24, 47, 99, 99, 99, 99, 87 18, 21, 26, 66, 99, 99, 99, 99, 88 24, 26, 56, 99, 99, 99, 99, 99, 89 47, 66, 99, 99, 99, 99, 99, 99, 90 99, 99, 99, 99, 99, 99, 99, 99, 91 99, 99, 99, 99, 99, 99, 99, 99, 92 99, 99, 99, 99, 99, 99, 99, 99, 93 99, 99, 99, 99, 99, 99, 99, 99 94 }; 95 96 97 #if JPEG_LIB_VERSION >= 70 98 GLOBAL(void) 99 jpeg_default_qtables(j_compress_ptr cinfo, boolean force_baseline) 100 /* Set or change the 'quality' (quantization) setting, using default tables 101 * and straight percentage-scaling quality scales. 102 * This entry point allows different scalings for luminance and chrominance. 103 */ 104 { 105 /* Set up two quantization tables using the specified scaling */ 106 jpeg_add_quant_table(cinfo, 0, std_luminance_quant_tbl, 107 cinfo->q_scale_factor[0], force_baseline); 108 jpeg_add_quant_table(cinfo, 1, std_chrominance_quant_tbl, 109 cinfo->q_scale_factor[1], force_baseline); 110 } 111 #endif 112 113 114 GLOBAL(void) 115 jpeg_set_linear_quality(j_compress_ptr cinfo, int scale_factor, 116 boolean force_baseline) 117 /* Set or change the 'quality' (quantization) setting, using default tables 118 * and a straight percentage-scaling quality scale. In most cases it's better 119 * to use jpeg_set_quality (below); this entry point is provided for 120 * applications that insist on a linear percentage scaling. 121 */ 122 { 123 /* Set up two quantization tables using the specified scaling */ 124 jpeg_add_quant_table(cinfo, 0, std_luminance_quant_tbl, 125 scale_factor, force_baseline); 126 jpeg_add_quant_table(cinfo, 1, std_chrominance_quant_tbl, 127 scale_factor, force_baseline); 128 } 129 130 131 GLOBAL(int) 132 jpeg_quality_scaling(int quality) 133 /* Convert a user-specified quality rating to a percentage scaling factor 134 * for an underlying quantization table, using our recommended scaling curve. 135 * The input 'quality' factor should be 0 (terrible) to 100 (very good). 136 */ 137 { 138 /* Safety limit on quality factor. Convert 0 to 1 to avoid zero divide. */ 139 if (quality <= 0) quality = 1; 140 if (quality > 100) quality = 100; 141 142 /* The basic table is used as-is (scaling 100) for a quality of 50. 143 * Qualities 50..100 are converted to scaling percentage 200 - 2*Q; 144 * note that at Q=100 the scaling is 0, which will cause jpeg_add_quant_table 145 * to make all the table entries 1 (hence, minimum quantization loss). 146 * Qualities 1..50 are converted to scaling percentage 5000/Q. 147 */ 148 if (quality < 50) 149 quality = 5000 / quality; 150 else 151 quality = 200 - quality * 2; 152 153 return quality; 154 } 155 156 157 GLOBAL(void) 158 jpeg_set_quality(j_compress_ptr cinfo, int quality, boolean force_baseline) 159 /* Set or change the 'quality' (quantization) setting, using default tables. 160 * This is the standard quality-adjusting entry point for typical user 161 * interfaces; only those who want detailed control over quantization tables 162 * would use the preceding three routines directly. 163 */ 164 { 165 /* Convert user 0-100 rating to percentage scaling */ 166 quality = jpeg_quality_scaling(quality); 167 168 /* Set up standard quality tables */ 169 jpeg_set_linear_quality(cinfo, quality, force_baseline); 170 } 171 172 173 /* 174 * Default parameter setup for compression. 175 * 176 * Applications that don't choose to use this routine must do their 177 * own setup of all these parameters. Alternately, you can call this 178 * to establish defaults and then alter parameters selectively. This 179 * is the recommended approach since, if we add any new parameters, 180 * your code will still work (they'll be set to reasonable defaults). 181 */ 182 183 GLOBAL(void) 184 jpeg_set_defaults(j_compress_ptr cinfo) 185 { 186 int i; 187 188 /* Safety check to ensure start_compress not called yet. */ 189 if (cinfo->global_state != CSTATE_START) 190 ERREXIT1(cinfo, JERR_BAD_STATE, cinfo->global_state); 191 192 /* Allocate comp_info array large enough for maximum component count. 193 * Array is made permanent in case application wants to compress 194 * multiple images at same param settings. 195 */ 196 if (cinfo->comp_info == NULL) 197 cinfo->comp_info = (jpeg_component_info *) 198 (*cinfo->mem->alloc_small) ((j_common_ptr)cinfo, JPOOL_PERMANENT, 199 MAX_COMPONENTS * sizeof(jpeg_component_info)); 200 201 /* Initialize everything not dependent on the color space */ 202 203 #if JPEG_LIB_VERSION >= 70 204 cinfo->scale_num = 1; /* 1:1 scaling */ 205 cinfo->scale_denom = 1; 206 #endif 207 /* Set up two quantization tables using default quality of 75 */ 208 jpeg_set_quality(cinfo, 75, TRUE); 209 /* Set up two Huffman tables */ 210 std_huff_tables((j_common_ptr)cinfo); 211 212 /* Initialize default arithmetic coding conditioning */ 213 for (i = 0; i < NUM_ARITH_TBLS; i++) { 214 cinfo->arith_dc_L[i] = 0; 215 cinfo->arith_dc_U[i] = 1; 216 cinfo->arith_ac_K[i] = 5; 217 } 218 219 /* Default is no multiple-scan output */ 220 cinfo->scan_info = NULL; 221 cinfo->num_scans = 0; 222 223 /* Expect normal source image, not raw downsampled data */ 224 cinfo->raw_data_in = FALSE; 225 226 /* Use Huffman coding, not arithmetic coding, by default */ 227 cinfo->arith_code = FALSE; 228 229 /* By default, don't do extra passes to optimize entropy coding */ 230 cinfo->optimize_coding = FALSE; 231 /* The standard Huffman tables are only valid for 8-bit data precision. 232 * If the precision is higher, force optimization on so that usable 233 * tables will be computed. This test can be removed if default tables 234 * are supplied that are valid for the desired precision. 235 */ 236 if (cinfo->data_precision == 12) 237 cinfo->optimize_coding = TRUE; 238 239 /* By default, use the simpler non-cosited sampling alignment */ 240 cinfo->CCIR601_sampling = FALSE; 241 242 #if JPEG_LIB_VERSION >= 70 243 /* By default, apply fancy downsampling */ 244 cinfo->do_fancy_downsampling = TRUE; 245 #endif 246 247 /* No input smoothing */ 248 cinfo->smoothing_factor = 0; 249 250 /* DCT algorithm preference */ 251 cinfo->dct_method = JDCT_DEFAULT; 252 253 /* No restart markers */ 254 cinfo->restart_interval = 0; 255 cinfo->restart_in_rows = 0; 256 257 /* Fill in default JFIF marker parameters. Note that whether the marker 258 * will actually be written is determined by jpeg_set_colorspace. 259 * 260 * By default, the library emits JFIF version code 1.01. 261 * An application that wants to emit JFIF 1.02 extension markers should set 262 * JFIF_minor_version to 2. We could probably get away with just defaulting 263 * to 1.02, but there may still be some decoders in use that will complain 264 * about that; saying 1.01 should minimize compatibility problems. 265 */ 266 cinfo->JFIF_major_version = 1; /* Default JFIF version = 1.01 */ 267 cinfo->JFIF_minor_version = 1; 268 cinfo->density_unit = 0; /* Pixel size is unknown by default */ 269 cinfo->X_density = 1; /* Pixel aspect ratio is square by default */ 270 cinfo->Y_density = 1; 271 272 /* Choose JPEG colorspace based on input space, set defaults accordingly */ 273 274 jpeg_default_colorspace(cinfo); 275 } 276 277 278 /* 279 * Select an appropriate JPEG colorspace for in_color_space. 280 */ 281 282 GLOBAL(void) 283 jpeg_default_colorspace(j_compress_ptr cinfo) 284 { 285 switch (cinfo->in_color_space) { 286 case JCS_GRAYSCALE: 287 jpeg_set_colorspace(cinfo, JCS_GRAYSCALE); 288 break; 289 case JCS_RGB: 290 case JCS_EXT_RGB: 291 case JCS_EXT_RGBX: 292 case JCS_EXT_BGR: 293 case JCS_EXT_BGRX: 294 case JCS_EXT_XBGR: 295 case JCS_EXT_XRGB: 296 case JCS_EXT_RGBA: 297 case JCS_EXT_BGRA: 298 case JCS_EXT_ABGR: 299 case JCS_EXT_ARGB: 300 if (cinfo->master->lossless) 301 jpeg_set_colorspace(cinfo, JCS_RGB); 302 else 303 jpeg_set_colorspace(cinfo, JCS_YCbCr); 304 break; 305 case JCS_YCbCr: 306 jpeg_set_colorspace(cinfo, JCS_YCbCr); 307 break; 308 case JCS_CMYK: 309 jpeg_set_colorspace(cinfo, JCS_CMYK); /* By default, no translation */ 310 break; 311 case JCS_YCCK: 312 jpeg_set_colorspace(cinfo, JCS_YCCK); 313 break; 314 case JCS_UNKNOWN: 315 jpeg_set_colorspace(cinfo, JCS_UNKNOWN); 316 break; 317 default: 318 ERREXIT(cinfo, JERR_BAD_IN_COLORSPACE); 319 } 320 } 321 322 323 /* 324 * Set the JPEG colorspace, and choose colorspace-dependent default values. 325 */ 326 327 GLOBAL(void) 328 jpeg_set_colorspace(j_compress_ptr cinfo, J_COLOR_SPACE colorspace) 329 { 330 jpeg_component_info *compptr; 331 int ci; 332 333 #define SET_COMP(index, id, hsamp, vsamp, quant, dctbl, actbl) \ 334 (compptr = &cinfo->comp_info[index], \ 335 compptr->component_id = (id), \ 336 compptr->h_samp_factor = (hsamp), \ 337 compptr->v_samp_factor = (vsamp), \ 338 compptr->quant_tbl_no = (quant), \ 339 compptr->dc_tbl_no = (dctbl), \ 340 compptr->ac_tbl_no = (actbl) ) 341 342 /* Safety check to ensure start_compress not called yet. */ 343 if (cinfo->global_state != CSTATE_START) 344 ERREXIT1(cinfo, JERR_BAD_STATE, cinfo->global_state); 345 346 /* For all colorspaces, we use Q and Huff tables 0 for luminance components, 347 * tables 1 for chrominance components. 348 */ 349 350 cinfo->jpeg_color_space = colorspace; 351 352 cinfo->write_JFIF_header = FALSE; /* No marker for non-JFIF colorspaces */ 353 cinfo->write_Adobe_marker = FALSE; /* write no Adobe marker by default */ 354 355 switch (colorspace) { 356 case JCS_GRAYSCALE: 357 cinfo->write_JFIF_header = TRUE; /* Write a JFIF marker */ 358 cinfo->num_components = 1; 359 /* JFIF specifies component ID 1 */ 360 SET_COMP(0, 1, 1, 1, 0, 0, 0); 361 break; 362 case JCS_RGB: 363 cinfo->write_Adobe_marker = TRUE; /* write Adobe marker to flag RGB */ 364 cinfo->num_components = 3; 365 SET_COMP(0, 0x52 /* 'R' */, 1, 1, 0, 0, 0); 366 SET_COMP(1, 0x47 /* 'G' */, 1, 1, 0, 0, 0); 367 SET_COMP(2, 0x42 /* 'B' */, 1, 1, 0, 0, 0); 368 break; 369 case JCS_YCbCr: 370 cinfo->write_JFIF_header = TRUE; /* Write a JFIF marker */ 371 cinfo->num_components = 3; 372 /* JFIF specifies component IDs 1,2,3 */ 373 /* We default to 2x2 subsamples of chrominance */ 374 SET_COMP(0, 1, 2, 2, 0, 0, 0); 375 SET_COMP(1, 2, 1, 1, 1, 1, 1); 376 SET_COMP(2, 3, 1, 1, 1, 1, 1); 377 break; 378 case JCS_CMYK: 379 cinfo->write_Adobe_marker = TRUE; /* write Adobe marker to flag CMYK */ 380 cinfo->num_components = 4; 381 SET_COMP(0, 0x43 /* 'C' */, 1, 1, 0, 0, 0); 382 SET_COMP(1, 0x4D /* 'M' */, 1, 1, 0, 0, 0); 383 SET_COMP(2, 0x59 /* 'Y' */, 1, 1, 0, 0, 0); 384 SET_COMP(3, 0x4B /* 'K' */, 1, 1, 0, 0, 0); 385 break; 386 case JCS_YCCK: 387 cinfo->write_Adobe_marker = TRUE; /* write Adobe marker to flag YCCK */ 388 cinfo->num_components = 4; 389 SET_COMP(0, 1, 2, 2, 0, 0, 0); 390 SET_COMP(1, 2, 1, 1, 1, 1, 1); 391 SET_COMP(2, 3, 1, 1, 1, 1, 1); 392 SET_COMP(3, 4, 2, 2, 0, 0, 0); 393 break; 394 case JCS_UNKNOWN: 395 cinfo->num_components = cinfo->input_components; 396 if (cinfo->num_components < 1 || cinfo->num_components > MAX_COMPONENTS) 397 ERREXIT2(cinfo, JERR_COMPONENT_COUNT, cinfo->num_components, 398 MAX_COMPONENTS); 399 for (ci = 0; ci < cinfo->num_components; ci++) { 400 SET_COMP(ci, ci, 1, 1, 0, 0, 0); 401 } 402 break; 403 default: 404 ERREXIT(cinfo, JERR_BAD_J_COLORSPACE); 405 } 406 } 407 408 409 #ifdef C_PROGRESSIVE_SUPPORTED 410 411 LOCAL(jpeg_scan_info *) 412 fill_a_scan(jpeg_scan_info *scanptr, int ci, int Ss, int Se, int Ah, int Al) 413 /* Support routine: generate one scan for specified component */ 414 { 415 scanptr->comps_in_scan = 1; 416 scanptr->component_index[0] = ci; 417 scanptr->Ss = Ss; 418 scanptr->Se = Se; 419 scanptr->Ah = Ah; 420 scanptr->Al = Al; 421 scanptr++; 422 return scanptr; 423 } 424 425 LOCAL(jpeg_scan_info *) 426 fill_scans(jpeg_scan_info *scanptr, int ncomps, int Ss, int Se, int Ah, int Al) 427 /* Support routine: generate one scan for each component */ 428 { 429 int ci; 430 431 for (ci = 0; ci < ncomps; ci++) { 432 scanptr->comps_in_scan = 1; 433 scanptr->component_index[0] = ci; 434 scanptr->Ss = Ss; 435 scanptr->Se = Se; 436 scanptr->Ah = Ah; 437 scanptr->Al = Al; 438 scanptr++; 439 } 440 return scanptr; 441 } 442 443 LOCAL(jpeg_scan_info *) 444 fill_dc_scans(jpeg_scan_info *scanptr, int ncomps, int Ah, int Al) 445 /* Support routine: generate interleaved DC scan if possible, else N scans */ 446 { 447 int ci; 448 449 if (ncomps <= MAX_COMPS_IN_SCAN) { 450 /* Single interleaved DC scan */ 451 scanptr->comps_in_scan = ncomps; 452 for (ci = 0; ci < ncomps; ci++) 453 scanptr->component_index[ci] = ci; 454 scanptr->Ss = scanptr->Se = 0; 455 scanptr->Ah = Ah; 456 scanptr->Al = Al; 457 scanptr++; 458 } else { 459 /* Noninterleaved DC scan for each component */ 460 scanptr = fill_scans(scanptr, ncomps, 0, 0, Ah, Al); 461 } 462 return scanptr; 463 } 464 465 466 /* 467 * Create a recommended progressive-JPEG script. 468 * cinfo->num_components and cinfo->jpeg_color_space must be correct. 469 */ 470 471 GLOBAL(void) 472 jpeg_simple_progression(j_compress_ptr cinfo) 473 { 474 int ncomps = cinfo->num_components; 475 int nscans; 476 jpeg_scan_info *scanptr; 477 478 /* Safety check to ensure start_compress not called yet. */ 479 if (cinfo->global_state != CSTATE_START) 480 ERREXIT1(cinfo, JERR_BAD_STATE, cinfo->global_state); 481 482 if (cinfo->master->lossless) { 483 cinfo->master->lossless = FALSE; 484 jpeg_default_colorspace(cinfo); 485 } 486 487 /* Figure space needed for script. Calculation must match code below! */ 488 if (ncomps == 3 && cinfo->jpeg_color_space == JCS_YCbCr) { 489 /* Custom script for YCbCr color images. */ 490 nscans = 10; 491 } else { 492 /* All-purpose script for other color spaces. */ 493 if (ncomps > MAX_COMPS_IN_SCAN) 494 nscans = 6 * ncomps; /* 2 DC + 4 AC scans per component */ 495 else 496 nscans = 2 + 4 * ncomps; /* 2 DC scans; 4 AC scans per component */ 497 } 498 499 /* Allocate space for script. 500 * We need to put it in the permanent pool in case the application performs 501 * multiple compressions without changing the settings. To avoid a memory 502 * leak if jpeg_simple_progression is called repeatedly for the same JPEG 503 * object, we try to re-use previously allocated space, and we allocate 504 * enough space to handle YCbCr even if initially asked for grayscale. 505 */ 506 if (cinfo->script_space == NULL || cinfo->script_space_size < nscans) { 507 cinfo->script_space_size = MAX(nscans, 10); 508 cinfo->script_space = (jpeg_scan_info *) 509 (*cinfo->mem->alloc_small) ((j_common_ptr)cinfo, JPOOL_PERMANENT, 510 cinfo->script_space_size * sizeof(jpeg_scan_info)); 511 } 512 scanptr = cinfo->script_space; 513 cinfo->scan_info = scanptr; 514 cinfo->num_scans = nscans; 515 516 if (ncomps == 3 && cinfo->jpeg_color_space == JCS_YCbCr) { 517 /* Custom script for YCbCr color images. */ 518 /* Initial DC scan */ 519 scanptr = fill_dc_scans(scanptr, ncomps, 0, 1); 520 /* Initial AC scan: get some luma data out in a hurry */ 521 scanptr = fill_a_scan(scanptr, 0, 1, 5, 0, 2); 522 /* Chroma data is too small to be worth expending many scans on */ 523 scanptr = fill_a_scan(scanptr, 2, 1, 63, 0, 1); 524 scanptr = fill_a_scan(scanptr, 1, 1, 63, 0, 1); 525 /* Complete spectral selection for luma AC */ 526 scanptr = fill_a_scan(scanptr, 0, 6, 63, 0, 2); 527 /* Refine next bit of luma AC */ 528 scanptr = fill_a_scan(scanptr, 0, 1, 63, 2, 1); 529 /* Finish DC successive approximation */ 530 scanptr = fill_dc_scans(scanptr, ncomps, 1, 0); 531 /* Finish AC successive approximation */ 532 scanptr = fill_a_scan(scanptr, 2, 1, 63, 1, 0); 533 scanptr = fill_a_scan(scanptr, 1, 1, 63, 1, 0); 534 /* Luma bottom bit comes last since it's usually largest scan */ 535 scanptr = fill_a_scan(scanptr, 0, 1, 63, 1, 0); 536 } else { 537 /* All-purpose script for other color spaces. */ 538 /* Successive approximation first pass */ 539 scanptr = fill_dc_scans(scanptr, ncomps, 0, 1); 540 scanptr = fill_scans(scanptr, ncomps, 1, 5, 0, 2); 541 scanptr = fill_scans(scanptr, ncomps, 6, 63, 0, 2); 542 /* Successive approximation second pass */ 543 scanptr = fill_scans(scanptr, ncomps, 1, 63, 2, 1); 544 /* Successive approximation final pass */ 545 scanptr = fill_dc_scans(scanptr, ncomps, 1, 0); 546 scanptr = fill_scans(scanptr, ncomps, 1, 63, 1, 0); 547 } 548 } 549 550 #endif /* C_PROGRESSIVE_SUPPORTED */ 551 552 553 #ifdef C_LOSSLESS_SUPPORTED 554 555 /* 556 * Enable lossless mode. 557 */ 558 559 GLOBAL(void) 560 jpeg_enable_lossless(j_compress_ptr cinfo, int predictor_selection_value, 561 int point_transform) 562 { 563 /* Safety check to ensure start_compress not called yet. */ 564 if (cinfo->global_state != CSTATE_START) 565 ERREXIT1(cinfo, JERR_BAD_STATE, cinfo->global_state); 566 567 cinfo->master->lossless = TRUE; 568 cinfo->Ss = predictor_selection_value; 569 cinfo->Se = 0; 570 cinfo->Ah = 0; 571 cinfo->Al = point_transform; 572 573 /* The JPEG spec simply gives the range 0..15 for Al (Pt), but that seems 574 * wrong: the upper bound ought to depend on data precision. Perhaps they 575 * really meant 0..N-1 for N-bit precision, which is what we allow here. 576 * Values greater than or equal to the data precision will result in a blank 577 * image. 578 */ 579 if (cinfo->Ss < 1 || cinfo->Ss > 7 || 580 cinfo->Al < 0 || cinfo->Al >= cinfo->data_precision) 581 ERREXIT4(cinfo, JERR_BAD_PROGRESSION, 582 cinfo->Ss, cinfo->Se, cinfo->Ah, cinfo->Al); 583 } 584 585 #endif /* C_LOSSLESS_SUPPORTED */