1/* 2 * jcparam.c 3 * 4 * Copyright (C) 1991-1998, Thomas G. Lane. 5 * Modified 2003-2008 by Guido Vollbeding. 6 * This file is part of the Independent JPEG Group's software. 7 * For conditions of distribution and use, see the accompanying README file. 8 * 9 * This file contains optional default-setting code for the JPEG compressor. 10 * Applications do not have to use this file, but those that don't use it 11 * must know a lot more about the innards of the JPEG code. 12 */ 13 14#define JPEG_INTERNALS 15#include "jinclude.h" 16#include "jpeglib.h" 17 18 19/* 20 * Quantization table setup routines 21 */ 22 23GLOBAL(void) 24jpeg_add_quant_table (j_compress_ptr cinfo, int which_tbl, 25 const unsigned int *basic_table, 26 int scale_factor, boolean force_baseline) 27/* Define a quantization table equal to the basic_table times 28 * a scale factor (given as a percentage). 29 * If force_baseline is TRUE, the computed quantization table entries 30 * are limited to 1..255 for JPEG baseline compatibility. 31 */ 32{ 33 JQUANT_TBL ** qtblptr; 34 int i; 35 long temp; 36 37 /* Safety check to ensure start_compress not called yet. */ 38 if (cinfo->global_state != CSTATE_START) 39 ERREXIT1(cinfo, JERR_BAD_STATE, cinfo->global_state); 40 41 if (which_tbl < 0 || which_tbl >= NUM_QUANT_TBLS) 42 ERREXIT1(cinfo, JERR_DQT_INDEX, which_tbl); 43 44 qtblptr = & cinfo->quant_tbl_ptrs[which_tbl]; 45 46 if (*qtblptr == NULL) 47 *qtblptr = jpeg_alloc_quant_table((j_common_ptr) cinfo); 48 49 for (i = 0; i < DCTSIZE2; i++) { 50 temp = ((long) basic_table[i] * scale_factor + 50L) / 100L; 51 /* limit the values to the valid range */ 52 if (temp <= 0L) temp = 1L; 53 if (temp > 32767L) temp = 32767L; /* max quantizer needed for 12 bits */ 54 if (force_baseline && temp > 255L) 55 temp = 255L; /* limit to baseline range if requested */ 56 (*qtblptr)->quantval[i] = (UINT16) temp; 57 } 58 59 /* Initialize sent_table FALSE so table will be written to JPEG file. */ 60 (*qtblptr)->sent_table = FALSE; 61} 62 63 64/* These are the sample quantization tables given in JPEG spec section K.1. 65 * The spec says that the values given produce "good" quality, and 66 * when divided by 2, "very good" quality. 67 */ 68static const unsigned int std_luminance_quant_tbl[DCTSIZE2] = { 69 16, 11, 10, 16, 24, 40, 51, 61, 70 12, 12, 14, 19, 26, 58, 60, 55, 71 14, 13, 16, 24, 40, 57, 69, 56, 72 14, 17, 22, 29, 51, 87, 80, 62, 73 18, 22, 37, 56, 68, 109, 103, 77, 74 24, 35, 55, 64, 81, 104, 113, 92, 75 49, 64, 78, 87, 103, 121, 120, 101, 76 72, 92, 95, 98, 112, 100, 103, 99 77}; 78static const unsigned int std_chrominance_quant_tbl[DCTSIZE2] = { 79 17, 18, 24, 47, 99, 99, 99, 99, 80 18, 21, 26, 66, 99, 99, 99, 99, 81 24, 26, 56, 99, 99, 99, 99, 99, 82 47, 66, 99, 99, 99, 99, 99, 99, 83 99, 99, 99, 99, 99, 99, 99, 99, 84 99, 99, 99, 99, 99, 99, 99, 99, 85 99, 99, 99, 99, 99, 99, 99, 99, 86 99, 99, 99, 99, 99, 99, 99, 99 87}; 88 89 90GLOBAL(void) 91jpeg_default_qtables (j_compress_ptr cinfo, boolean force_baseline) 92/* Set or change the 'quality' (quantization) setting, using default tables 93 * and straight percentage-scaling quality scales. 94 * This entry point allows different scalings for luminance and chrominance. 95 */ 96{ 97 /* Set up two quantization tables using the specified scaling */ 98 jpeg_add_quant_table(cinfo, 0, std_luminance_quant_tbl, 99 cinfo->q_scale_factor[0], force_baseline); 100 jpeg_add_quant_table(cinfo, 1, std_chrominance_quant_tbl, 101 cinfo->q_scale_factor[1], force_baseline); 102} 103 104 105GLOBAL(void) 106jpeg_set_linear_quality (j_compress_ptr cinfo, int scale_factor, 107 boolean force_baseline) 108/* Set or change the 'quality' (quantization) setting, using default tables 109 * and a straight percentage-scaling quality scale. In most cases it's better 110 * to use jpeg_set_quality (below); this entry point is provided for 111 * applications that insist on a linear percentage scaling. 112 */ 113{ 114 /* Set up two quantization tables using the specified scaling */ 115 jpeg_add_quant_table(cinfo, 0, std_luminance_quant_tbl, 116 scale_factor, force_baseline); 117 jpeg_add_quant_table(cinfo, 1, std_chrominance_quant_tbl, 118 scale_factor, force_baseline); 119} 120 121 122GLOBAL(int) 123jpeg_quality_scaling (int quality) 124/* Convert a user-specified quality rating to a percentage scaling factor 125 * for an underlying quantization table, using our recommended scaling curve. 126 * The input 'quality' factor should be 0 (terrible) to 100 (very good). 127 */ 128{ 129 /* Safety limit on quality factor. Convert 0 to 1 to avoid zero divide. */ 130 if (quality <= 0) quality = 1; 131 if (quality > 100) quality = 100; 132 133 /* The basic table is used as-is (scaling 100) for a quality of 50. 134 * Qualities 50..100 are converted to scaling percentage 200 - 2*Q; 135 * note that at Q=100 the scaling is 0, which will cause jpeg_add_quant_table 136 * to make all the table entries 1 (hence, minimum quantization loss). 137 * Qualities 1..50 are converted to scaling percentage 5000/Q. 138 */ 139 if (quality < 50) 140 quality = 5000 / quality; 141 else 142 quality = 200 - quality*2; 143 144 return quality; 145} 146 147 148GLOBAL(void) 149jpeg_set_quality (j_compress_ptr cinfo, int quality, boolean force_baseline) 150/* Set or change the 'quality' (quantization) setting, using default tables. 151 * This is the standard quality-adjusting entry point for typical user 152 * interfaces; only those who want detailed control over quantization tables 153 * would use the preceding three routines directly. 154 */ 155{ 156 /* Convert user 0-100 rating to percentage scaling */ 157 quality = jpeg_quality_scaling(quality); 158 159 /* Set up standard quality tables */ 160 jpeg_set_linear_quality(cinfo, quality, force_baseline); 161} 162 163 164/* 165 * Huffman table setup routines 166 */ 167 168LOCAL(void) 169add_huff_table (j_compress_ptr cinfo, 170 JHUFF_TBL **htblptr, const UINT8 *bits, const UINT8 *val) 171/* Define a Huffman table */ 172{ 173 int nsymbols, len; 174 175 if (*htblptr == NULL) 176 *htblptr = jpeg_alloc_huff_table((j_common_ptr) cinfo); 177 178 /* Copy the number-of-symbols-of-each-code-length counts */ 179 MEMCOPY((*htblptr)->bits, bits, SIZEOF((*htblptr)->bits)); 180 181 /* Validate the counts. We do this here mainly so we can copy the right 182 * number of symbols from the val[] array, without risking marching off 183 * the end of memory. jchuff.c will do a more thorough test later. 184 */ 185 nsymbols = 0; 186 for (len = 1; len <= 16; len++) 187 nsymbols += bits[len]; 188 if (nsymbols < 1 || nsymbols > 256) 189 ERREXIT(cinfo, JERR_BAD_HUFF_TABLE); 190 191 MEMCOPY((*htblptr)->huffval, val, nsymbols * SIZEOF(UINT8)); 192 193 /* Initialize sent_table FALSE so table will be written to JPEG file. */ 194 (*htblptr)->sent_table = FALSE; 195} 196 197 198LOCAL(void) 199std_huff_tables (j_compress_ptr cinfo) 200/* Set up the standard Huffman tables (cf. JPEG standard section K.3) */ 201/* IMPORTANT: these are only valid for 8-bit data precision! */ 202{ 203 static const UINT8 bits_dc_luminance[17] = 204 { /* 0-base */ 0, 0, 1, 5, 1, 1, 1, 1, 1, 1, 0, 0, 0, 0, 0, 0, 0 }; 205 static const UINT8 val_dc_luminance[] = 206 { 0, 1, 2, 3, 4, 5, 6, 7, 8, 9, 10, 11 }; 207 208 static const UINT8 bits_dc_chrominance[17] = 209 { /* 0-base */ 0, 0, 3, 1, 1, 1, 1, 1, 1, 1, 1, 1, 0, 0, 0, 0, 0 }; 210 static const UINT8 val_dc_chrominance[] = 211 { 0, 1, 2, 3, 4, 5, 6, 7, 8, 9, 10, 11 }; 212 213 static const UINT8 bits_ac_luminance[17] = 214 { /* 0-base */ 0, 0, 2, 1, 3, 3, 2, 4, 3, 5, 5, 4, 4, 0, 0, 1, 0x7d }; 215 static const UINT8 val_ac_luminance[] = 216 { 0x01, 0x02, 0x03, 0x00, 0x04, 0x11, 0x05, 0x12, 217 0x21, 0x31, 0x41, 0x06, 0x13, 0x51, 0x61, 0x07, 218 0x22, 0x71, 0x14, 0x32, 0x81, 0x91, 0xa1, 0x08, 219 0x23, 0x42, 0xb1, 0xc1, 0x15, 0x52, 0xd1, 0xf0, 220 0x24, 0x33, 0x62, 0x72, 0x82, 0x09, 0x0a, 0x16, 221 0x17, 0x18, 0x19, 0x1a, 0x25, 0x26, 0x27, 0x28, 222 0x29, 0x2a, 0x34, 0x35, 0x36, 0x37, 0x38, 0x39, 223 0x3a, 0x43, 0x44, 0x45, 0x46, 0x47, 0x48, 0x49, 224 0x4a, 0x53, 0x54, 0x55, 0x56, 0x57, 0x58, 0x59, 225 0x5a, 0x63, 0x64, 0x65, 0x66, 0x67, 0x68, 0x69, 226 0x6a, 0x73, 0x74, 0x75, 0x76, 0x77, 0x78, 0x79, 227 0x7a, 0x83, 0x84, 0x85, 0x86, 0x87, 0x88, 0x89, 228 0x8a, 0x92, 0x93, 0x94, 0x95, 0x96, 0x97, 0x98, 229 0x99, 0x9a, 0xa2, 0xa3, 0xa4, 0xa5, 0xa6, 0xa7, 230 0xa8, 0xa9, 0xaa, 0xb2, 0xb3, 0xb4, 0xb5, 0xb6, 231 0xb7, 0xb8, 0xb9, 0xba, 0xc2, 0xc3, 0xc4, 0xc5, 232 0xc6, 0xc7, 0xc8, 0xc9, 0xca, 0xd2, 0xd3, 0xd4, 233 0xd5, 0xd6, 0xd7, 0xd8, 0xd9, 0xda, 0xe1, 0xe2, 234 0xe3, 0xe4, 0xe5, 0xe6, 0xe7, 0xe8, 0xe9, 0xea, 235 0xf1, 0xf2, 0xf3, 0xf4, 0xf5, 0xf6, 0xf7, 0xf8, 236 0xf9, 0xfa }; 237 238 static const UINT8 bits_ac_chrominance[17] = 239 { /* 0-base */ 0, 0, 2, 1, 2, 4, 4, 3, 4, 7, 5, 4, 4, 0, 1, 2, 0x77 }; 240 static const UINT8 val_ac_chrominance[] = 241 { 0x00, 0x01, 0x02, 0x03, 0x11, 0x04, 0x05, 0x21, 242 0x31, 0x06, 0x12, 0x41, 0x51, 0x07, 0x61, 0x71, 243 0x13, 0x22, 0x32, 0x81, 0x08, 0x14, 0x42, 0x91, 244 0xa1, 0xb1, 0xc1, 0x09, 0x23, 0x33, 0x52, 0xf0, 245 0x15, 0x62, 0x72, 0xd1, 0x0a, 0x16, 0x24, 0x34, 246 0xe1, 0x25, 0xf1, 0x17, 0x18, 0x19, 0x1a, 0x26, 247 0x27, 0x28, 0x29, 0x2a, 0x35, 0x36, 0x37, 0x38, 248 0x39, 0x3a, 0x43, 0x44, 0x45, 0x46, 0x47, 0x48, 249 0x49, 0x4a, 0x53, 0x54, 0x55, 0x56, 0x57, 0x58, 250 0x59, 0x5a, 0x63, 0x64, 0x65, 0x66, 0x67, 0x68, 251 0x69, 0x6a, 0x73, 0x74, 0x75, 0x76, 0x77, 0x78, 252 0x79, 0x7a, 0x82, 0x83, 0x84, 0x85, 0x86, 0x87, 253 0x88, 0x89, 0x8a, 0x92, 0x93, 0x94, 0x95, 0x96, 254 0x97, 0x98, 0x99, 0x9a, 0xa2, 0xa3, 0xa4, 0xa5, 255 0xa6, 0xa7, 0xa8, 0xa9, 0xaa, 0xb2, 0xb3, 0xb4, 256 0xb5, 0xb6, 0xb7, 0xb8, 0xb9, 0xba, 0xc2, 0xc3, 257 0xc4, 0xc5, 0xc6, 0xc7, 0xc8, 0xc9, 0xca, 0xd2, 258 0xd3, 0xd4, 0xd5, 0xd6, 0xd7, 0xd8, 0xd9, 0xda, 259 0xe2, 0xe3, 0xe4, 0xe5, 0xe6, 0xe7, 0xe8, 0xe9, 260 0xea, 0xf2, 0xf3, 0xf4, 0xf5, 0xf6, 0xf7, 0xf8, 261 0xf9, 0xfa }; 262 263 add_huff_table(cinfo, &cinfo->dc_huff_tbl_ptrs[0], 264 bits_dc_luminance, val_dc_luminance); 265 add_huff_table(cinfo, &cinfo->ac_huff_tbl_ptrs[0], 266 bits_ac_luminance, val_ac_luminance); 267 add_huff_table(cinfo, &cinfo->dc_huff_tbl_ptrs[1], 268 bits_dc_chrominance, val_dc_chrominance); 269 add_huff_table(cinfo, &cinfo->ac_huff_tbl_ptrs[1], 270 bits_ac_chrominance, val_ac_chrominance); 271} 272 273 274/* 275 * Default parameter setup for compression. 276 * 277 * Applications that don't choose to use this routine must do their 278 * own setup of all these parameters. Alternately, you can call this 279 * to establish defaults and then alter parameters selectively. This 280 * is the recommended approach since, if we add any new parameters, 281 * your code will still work (they'll be set to reasonable defaults). 282 */ 283 284GLOBAL(void) 285jpeg_set_defaults (j_compress_ptr cinfo) 286{ 287 int i; 288 289 /* Safety check to ensure start_compress not called yet. */ 290 if (cinfo->global_state != CSTATE_START) 291 ERREXIT1(cinfo, JERR_BAD_STATE, cinfo->global_state); 292 293 /* Allocate comp_info array large enough for maximum component count. 294 * Array is made permanent in case application wants to compress 295 * multiple images at same param settings. 296 */ 297 if (cinfo->comp_info == NULL) 298 cinfo->comp_info = (jpeg_component_info *) 299 (*cinfo->mem->alloc_small) ((j_common_ptr) cinfo, JPOOL_PERMANENT, 300 MAX_COMPONENTS * SIZEOF(jpeg_component_info)); 301 302 /* Initialize everything not dependent on the color space */ 303 304 cinfo->scale_num = 1; /* 1:1 scaling */ 305 cinfo->scale_denom = 1; 306 cinfo->data_precision = BITS_IN_JSAMPLE; 307 /* Set up two quantization tables using default quality of 75 */ 308 jpeg_set_quality(cinfo, 75, TRUE); 309 /* Set up two Huffman tables */ 310 std_huff_tables(cinfo); 311 312 /* Initialize default arithmetic coding conditioning */ 313 for (i = 0; i < NUM_ARITH_TBLS; i++) { 314 cinfo->arith_dc_L[i] = 0; 315 cinfo->arith_dc_U[i] = 1; 316 cinfo->arith_ac_K[i] = 5; 317 } 318 319 /* Default is no multiple-scan output */ 320 cinfo->scan_info = NULL; 321 cinfo->num_scans = 0; 322 323 /* Expect normal source image, not raw downsampled data */ 324 cinfo->raw_data_in = FALSE; 325 326 /* Use Huffman coding, not arithmetic coding, by default */ 327 cinfo->arith_code = FALSE; 328 329 /* By default, don't do extra passes to optimize entropy coding */ 330 cinfo->optimize_coding = FALSE; 331 /* The standard Huffman tables are only valid for 8-bit data precision. 332 * If the precision is higher, force optimization on so that usable 333 * tables will be computed. This test can be removed if default tables 334 * are supplied that are valid for the desired precision. 335 */ 336 if (cinfo->data_precision > 8) 337 cinfo->optimize_coding = TRUE; 338 339 /* By default, use the simpler non-cosited sampling alignment */ 340 cinfo->CCIR601_sampling = FALSE; 341 342 /* By default, apply fancy downsampling */ 343 cinfo->do_fancy_downsampling = TRUE; 344 345 /* No input smoothing */ 346 cinfo->smoothing_factor = 0; 347 348 /* DCT algorithm preference */ 349 cinfo->dct_method = JDCT_DEFAULT; 350 351 /* No restart markers */ 352 cinfo->restart_interval = 0; 353 cinfo->restart_in_rows = 0; 354 355 /* Fill in default JFIF marker parameters. Note that whether the marker 356 * will actually be written is determined by jpeg_set_colorspace. 357 * 358 * By default, the library emits JFIF version code 1.01. 359 * An application that wants to emit JFIF 1.02 extension markers should set 360 * JFIF_minor_version to 2. We could probably get away with just defaulting 361 * to 1.02, but there may still be some decoders in use that will complain 362 * about that; saying 1.01 should minimize compatibility problems. 363 */ 364 cinfo->JFIF_major_version = 1; /* Default JFIF version = 1.01 */ 365 cinfo->JFIF_minor_version = 1; 366 cinfo->density_unit = 0; /* Pixel size is unknown by default */ 367 cinfo->X_density = 1; /* Pixel aspect ratio is square by default */ 368 cinfo->Y_density = 1; 369 370 /* Choose JPEG colorspace based on input space, set defaults accordingly */ 371 372 jpeg_default_colorspace(cinfo); 373} 374 375 376/* 377 * Select an appropriate JPEG colorspace for in_color_space. 378 */ 379 380GLOBAL(void) 381jpeg_default_colorspace (j_compress_ptr cinfo) 382{ 383 switch (cinfo->in_color_space) { 384 case JCS_GRAYSCALE: 385 jpeg_set_colorspace(cinfo, JCS_GRAYSCALE); 386 break; 387 case JCS_RGB: 388 jpeg_set_colorspace(cinfo, JCS_YCbCr); 389 break; 390 case JCS_YCbCr: 391 jpeg_set_colorspace(cinfo, JCS_YCbCr); 392 break; 393 case JCS_CMYK: 394 jpeg_set_colorspace(cinfo, JCS_CMYK); /* By default, no translation */ 395 break; 396 case JCS_YCCK: 397 jpeg_set_colorspace(cinfo, JCS_YCCK); 398 break; 399 case JCS_UNKNOWN: 400 jpeg_set_colorspace(cinfo, JCS_UNKNOWN); 401 break; 402 default: 403 ERREXIT(cinfo, JERR_BAD_IN_COLORSPACE); 404 } 405} 406 407 408/* 409 * Set the JPEG colorspace, and choose colorspace-dependent default values. 410 */ 411 412GLOBAL(void) 413jpeg_set_colorspace (j_compress_ptr cinfo, J_COLOR_SPACE colorspace) 414{ 415 jpeg_component_info * compptr; 416 int ci; 417 418#define SET_COMP(index,id,hsamp,vsamp,quant,dctbl,actbl) \ 419 (compptr = &cinfo->comp_info[index], \ 420 compptr->component_id = (id), \ 421 compptr->h_samp_factor = (hsamp), \ 422 compptr->v_samp_factor = (vsamp), \ 423 compptr->quant_tbl_no = (quant), \ 424 compptr->dc_tbl_no = (dctbl), \ 425 compptr->ac_tbl_no = (actbl) ) 426 427 /* Safety check to ensure start_compress not called yet. */ 428 if (cinfo->global_state != CSTATE_START) 429 ERREXIT1(cinfo, JERR_BAD_STATE, cinfo->global_state); 430 431 /* For all colorspaces, we use Q and Huff tables 0 for luminance components, 432 * tables 1 for chrominance components. 433 */ 434 435 cinfo->jpeg_color_space = colorspace; 436 437 cinfo->write_JFIF_header = FALSE; /* No marker for non-JFIF colorspaces */ 438 cinfo->write_Adobe_marker = FALSE; /* write no Adobe marker by default */ 439 440 switch (colorspace) { 441 case JCS_GRAYSCALE: 442 cinfo->write_JFIF_header = TRUE; /* Write a JFIF marker */ 443 cinfo->num_components = 1; 444 /* JFIF specifies component ID 1 */ 445 SET_COMP(0, 1, 1,1, 0, 0,0); 446 break; 447 case JCS_RGB: 448 cinfo->write_Adobe_marker = TRUE; /* write Adobe marker to flag RGB */ 449 cinfo->num_components = 3; 450 SET_COMP(0, 0x52 /* 'R' */, 1,1, 0, 0,0); 451 SET_COMP(1, 0x47 /* 'G' */, 1,1, 0, 0,0); 452 SET_COMP(2, 0x42 /* 'B' */, 1,1, 0, 0,0); 453 break; 454 case JCS_YCbCr: 455 cinfo->write_JFIF_header = TRUE; /* Write a JFIF marker */ 456 cinfo->num_components = 3; 457 /* JFIF specifies component IDs 1,2,3 */ 458 /* We default to 2x2 subsamples of chrominance */ 459 SET_COMP(0, 1, 2,2, 0, 0,0); 460 SET_COMP(1, 2, 1,1, 1, 1,1); 461 SET_COMP(2, 3, 1,1, 1, 1,1); 462 break; 463 case JCS_CMYK: 464 cinfo->write_Adobe_marker = TRUE; /* write Adobe marker to flag CMYK */ 465 cinfo->num_components = 4; 466 SET_COMP(0, 0x43 /* 'C' */, 1,1, 0, 0,0); 467 SET_COMP(1, 0x4D /* 'M' */, 1,1, 0, 0,0); 468 SET_COMP(2, 0x59 /* 'Y' */, 1,1, 0, 0,0); 469 SET_COMP(3, 0x4B /* 'K' */, 1,1, 0, 0,0); 470 break; 471 case JCS_YCCK: 472 cinfo->write_Adobe_marker = TRUE; /* write Adobe marker to flag YCCK */ 473 cinfo->num_components = 4; 474 SET_COMP(0, 1, 2,2, 0, 0,0); 475 SET_COMP(1, 2, 1,1, 1, 1,1); 476 SET_COMP(2, 3, 1,1, 1, 1,1); 477 SET_COMP(3, 4, 2,2, 0, 0,0); 478 break; 479 case JCS_UNKNOWN: 480 cinfo->num_components = cinfo->input_components; 481 if (cinfo->num_components < 1 || cinfo->num_components > MAX_COMPONENTS) 482 ERREXIT2(cinfo, JERR_COMPONENT_COUNT, cinfo->num_components, 483 MAX_COMPONENTS); 484 for (ci = 0; ci < cinfo->num_components; ci++) { 485 SET_COMP(ci, ci, 1,1, 0, 0,0); 486 } 487 break; 488 default: 489 ERREXIT(cinfo, JERR_BAD_J_COLORSPACE); 490 } 491} 492 493 494#ifdef C_PROGRESSIVE_SUPPORTED 495 496LOCAL(jpeg_scan_info *) 497fill_a_scan (jpeg_scan_info * scanptr, int ci, 498 int Ss, int Se, int Ah, int Al) 499/* Support routine: generate one scan for specified component */ 500{ 501 scanptr->comps_in_scan = 1; 502 scanptr->component_index[0] = ci; 503 scanptr->Ss = Ss; 504 scanptr->Se = Se; 505 scanptr->Ah = Ah; 506 scanptr->Al = Al; 507 scanptr++; 508 return scanptr; 509} 510 511LOCAL(jpeg_scan_info *) 512fill_scans (jpeg_scan_info * scanptr, int ncomps, 513 int Ss, int Se, int Ah, int Al) 514/* Support routine: generate one scan for each component */ 515{ 516 int ci; 517 518 for (ci = 0; ci < ncomps; ci++) { 519 scanptr->comps_in_scan = 1; 520 scanptr->component_index[0] = ci; 521 scanptr->Ss = Ss; 522 scanptr->Se = Se; 523 scanptr->Ah = Ah; 524 scanptr->Al = Al; 525 scanptr++; 526 } 527 return scanptr; 528} 529 530LOCAL(jpeg_scan_info *) 531fill_dc_scans (jpeg_scan_info * scanptr, int ncomps, int Ah, int Al) 532/* Support routine: generate interleaved DC scan if possible, else N scans */ 533{ 534 int ci; 535 536 if (ncomps <= MAX_COMPS_IN_SCAN) { 537 /* Single interleaved DC scan */ 538 scanptr->comps_in_scan = ncomps; 539 for (ci = 0; ci < ncomps; ci++) 540 scanptr->component_index[ci] = ci; 541 scanptr->Ss = scanptr->Se = 0; 542 scanptr->Ah = Ah; 543 scanptr->Al = Al; 544 scanptr++; 545 } else { 546 /* Noninterleaved DC scan for each component */ 547 scanptr = fill_scans(scanptr, ncomps, 0, 0, Ah, Al); 548 } 549 return scanptr; 550} 551 552 553/* 554 * Create a recommended progressive-JPEG script. 555 * cinfo->num_components and cinfo->jpeg_color_space must be correct. 556 */ 557 558GLOBAL(void) 559jpeg_simple_progression (j_compress_ptr cinfo) 560{ 561 int ncomps = cinfo->num_components; 562 int nscans; 563 jpeg_scan_info * scanptr; 564 565 /* Safety check to ensure start_compress not called yet. */ 566 if (cinfo->global_state != CSTATE_START) 567 ERREXIT1(cinfo, JERR_BAD_STATE, cinfo->global_state); 568 569 /* Figure space needed for script. Calculation must match code below! */ 570 if (ncomps == 3 && cinfo->jpeg_color_space == JCS_YCbCr) { 571 /* Custom script for YCbCr color images. */ 572 nscans = 10; 573 } else { 574 /* All-purpose script for other color spaces. */ 575 if (ncomps > MAX_COMPS_IN_SCAN) 576 nscans = 6 * ncomps; /* 2 DC + 4 AC scans per component */ 577 else 578 nscans = 2 + 4 * ncomps; /* 2 DC scans; 4 AC scans per component */ 579 } 580 581 /* Allocate space for script. 582 * We need to put it in the permanent pool in case the application performs 583 * multiple compressions without changing the settings. To avoid a memory 584 * leak if jpeg_simple_progression is called repeatedly for the same JPEG 585 * object, we try to re-use previously allocated space, and we allocate 586 * enough space to handle YCbCr even if initially asked for grayscale. 587 */ 588 if (cinfo->script_space == NULL || cinfo->script_space_size < nscans) { 589 cinfo->script_space_size = MAX(nscans, 10); 590 cinfo->script_space = (jpeg_scan_info *) 591 (*cinfo->mem->alloc_small) ((j_common_ptr) cinfo, JPOOL_PERMANENT, 592 cinfo->script_space_size * SIZEOF(jpeg_scan_info)); 593 } 594 scanptr = cinfo->script_space; 595 cinfo->scan_info = scanptr; 596 cinfo->num_scans = nscans; 597 598 if (ncomps == 3 && cinfo->jpeg_color_space == JCS_YCbCr) { 599 /* Custom script for YCbCr color images. */ 600 /* Initial DC scan */ 601 scanptr = fill_dc_scans(scanptr, ncomps, 0, 1); 602 /* Initial AC scan: get some luma data out in a hurry */ 603 scanptr = fill_a_scan(scanptr, 0, 1, 5, 0, 2); 604 /* Chroma data is too small to be worth expending many scans on */ 605 scanptr = fill_a_scan(scanptr, 2, 1, 63, 0, 1); 606 scanptr = fill_a_scan(scanptr, 1, 1, 63, 0, 1); 607 /* Complete spectral selection for luma AC */ 608 scanptr = fill_a_scan(scanptr, 0, 6, 63, 0, 2); 609 /* Refine next bit of luma AC */ 610 scanptr = fill_a_scan(scanptr, 0, 1, 63, 2, 1); 611 /* Finish DC successive approximation */ 612 scanptr = fill_dc_scans(scanptr, ncomps, 1, 0); 613 /* Finish AC successive approximation */ 614 scanptr = fill_a_scan(scanptr, 2, 1, 63, 1, 0); 615 scanptr = fill_a_scan(scanptr, 1, 1, 63, 1, 0); 616 /* Luma bottom bit comes last since it's usually largest scan */ 617 scanptr = fill_a_scan(scanptr, 0, 1, 63, 1, 0); 618 } else { 619 /* All-purpose script for other color spaces. */ 620 /* Successive approximation first pass */ 621 scanptr = fill_dc_scans(scanptr, ncomps, 0, 1); 622 scanptr = fill_scans(scanptr, ncomps, 1, 5, 0, 2); 623 scanptr = fill_scans(scanptr, ncomps, 6, 63, 0, 2); 624 /* Successive approximation second pass */ 625 scanptr = fill_scans(scanptr, ncomps, 1, 63, 2, 1); 626 /* Successive approximation final pass */ 627 scanptr = fill_dc_scans(scanptr, ncomps, 1, 0); 628 scanptr = fill_scans(scanptr, ncomps, 1, 63, 1, 0); 629 } 630} 631 632#endif /* C_PROGRESSIVE_SUPPORTED */ 633