src/jpeg/jcmarker.c

   1 /*
   2  * jcmarker.c
   3  *
   4  * Copyright (C) 1991-1998, 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 routines to write JPEG datastream markers.
   9  */
  10
  11 #define JPEG_INTERNALS
  12 #include "jinclude.h"
  13 #include "jpeglib.h"
  14
  15
  16 typedef enum {                  /* JPEG marker codes */
  17   M_SOF0  = 0xc0,
  18   M_SOF1  = 0xc1,
  19   M_SOF2  = 0xc2,
  20   M_SOF3  = 0xc3,
  21
  22   M_SOF5  = 0xc5,
  23   M_SOF6  = 0xc6,
  24   M_SOF7  = 0xc7,
  25
  26   M_JPG   = 0xc8,
  27   M_SOF9  = 0xc9,
  28   M_SOF10 = 0xca,
  29   M_SOF11 = 0xcb,
  30
  31   M_SOF13 = 0xcd,
  32   M_SOF14 = 0xce,
  33   M_SOF15 = 0xcf,
  34
  35   M_DHT   = 0xc4,
  36
  37   M_DAC   = 0xcc,
  38
  39   M_RST0  = 0xd0,
  40   M_RST1  = 0xd1,
  41   M_RST2  = 0xd2,
  42   M_RST3  = 0xd3,
  43   M_RST4  = 0xd4,
  44   M_RST5  = 0xd5,
  45   M_RST6  = 0xd6,
  46   M_RST7  = 0xd7,
  47
  48   M_SOI   = 0xd8,
  49   M_EOI   = 0xd9,
  50   M_SOS   = 0xda,
  51   M_DQT   = 0xdb,
  52   M_DNL   = 0xdc,
  53   M_DRI   = 0xdd,
  54   M_DHP   = 0xde,
  55   M_EXP   = 0xdf,
  56
  57   M_APP0  = 0xe0,
  58   M_APP1  = 0xe1,
  59   M_APP2  = 0xe2,
  60   M_APP3  = 0xe3,
  61   M_APP4  = 0xe4,
  62   M_APP5  = 0xe5,
  63   M_APP6  = 0xe6,
  64   M_APP7  = 0xe7,
  65   M_APP8  = 0xe8,
  66   M_APP9  = 0xe9,
  67   M_APP10 = 0xea,
  68   M_APP11 = 0xeb,
  69   M_APP12 = 0xec,
  70   M_APP13 = 0xed,
  71   M_APP14 = 0xee,
  72   M_APP15 = 0xef,
  73
  74   M_JPG0  = 0xf0,
  75   M_JPG13 = 0xfd,
  76   M_COM   = 0xfe,
  77
  78   M_TEM   = 0x01,
  79
  80   M_ERROR = 0x100
  81 } JPEG_MARKER;
  82
  83
  84 /* Private state */
  85
  86 typedef struct {
  87   struct jpeg_marker_writer pub; /* public fields */
  88
  89   unsigned int last_restart_interval; /* last DRI value emitted; 0 after SOI */
  90 } my_marker_writer;
  91
  92 typedef my_marker_writer * my_marker_ptr;
  93
  94
  95 /*
  96  * Basic output routines.
  97  *
  98  * Note that we do not support suspension while writing a marker.
  99  * Therefore, an application using suspension must ensure that there is
 100  * enough buffer space for the initial markers (typ. 600-700 bytes) before
 101  * calling jpeg_start_compress, and enough space to write the trailing EOI
 102  * (a few bytes) before calling jpeg_finish_compress.  Multipass compression
 103  * modes are not supported at all with suspension, so those two are the only
 104  * points where markers will be written.
 105  */
 106
 107 LOCAL(void)
 108 emit_byte (j_compress_ptr cinfo, int val)
 109 /* Emit a byte */
 110 {
 111   struct jpeg_destination_mgr * dest = cinfo->dest;
 112
 113   *(dest->next_output_byte)++ = (JOCTET) val;
 114   if (--dest->free_in_buffer == 0) {
 115     if (! (*dest->empty_output_buffer) (cinfo))
 116       ERREXIT(cinfo, JERR_CANT_SUSPEND);
 117   }
 118 }
 119
 120
 121 LOCAL(void)
 122 emit_marker (j_compress_ptr cinfo, JPEG_MARKER mark)
 123 /* Emit a marker code */
 124 {
 125   emit_byte(cinfo, 0xFF);
 126   emit_byte(cinfo, (int) mark);
 127 }
 128
 129
 130 LOCAL(void)
 131 emit_2bytes (j_compress_ptr cinfo, int value)
 132 /* Emit a 2-byte integer; these are always MSB first in JPEG files */
 133 {
 134   emit_byte(cinfo, (value >> 8) & 0xFF);
 135   emit_byte(cinfo, value & 0xFF);
 136 }
 137
 138
 139 /*
 140  * Routines to write specific marker types.
 141  */
 142
 143 LOCAL(int)
 144 emit_dqt (j_compress_ptr cinfo, int index)
 145 /* Emit a DQT marker */
 146 /* Returns the precision used (0 = 8bits, 1 = 16bits) for baseline checking */
 147 {
 148   JQUANT_TBL * qtbl = cinfo->quant_tbl_ptrs[index];
 149   int prec;
 150   int i;
 151
 152   if (qtbl == NULL)
 153     ERREXIT1(cinfo, JERR_NO_QUANT_TABLE, index);
 154
 155   prec = 0;
 156   for (i = 0; i < DCTSIZE2; i++) {
 157     if (qtbl->quantval[i] > 255)
 158       prec = 1;
 159   }
 160
 161   if (! qtbl->sent_table) {
 162     emit_marker(cinfo, M_DQT);
 163
 164     emit_2bytes(cinfo, prec ? DCTSIZE2*2 + 1 + 2 : DCTSIZE2 + 1 + 2);
 165
 166     emit_byte(cinfo, index + (prec<<4));
 167
 168     for (i = 0; i < DCTSIZE2; i++) {
 169       /* The table entries must be emitted in zigzag order. */
 170       unsigned int qval = qtbl->quantval[jpeg_natural_order[i]];
 171       if (prec)
 172         emit_byte(cinfo, (int) (qval >> 8));
 173       emit_byte(cinfo, (int) (qval & 0xFF));
 174     }
 175
 176     qtbl->sent_table = TRUE;
 177   }
 178
 179   return prec;
 180 }
 181
 182
 183 LOCAL(void)
 184 emit_dht (j_compress_ptr cinfo, int index, boolean is_ac)
 185 /* Emit a DHT marker */
 186 {
 187   JHUFF_TBL * htbl;
 188   int length, i;
 189
 190   if (is_ac) {
 191     htbl = cinfo->ac_huff_tbl_ptrs[index];
 192     index += 0x10;              /* output index has AC bit set */
 193   } else {
 194     htbl = cinfo->dc_huff_tbl_ptrs[index];
 195   }
 196
 197   if (htbl == NULL)
 198     ERREXIT1(cinfo, JERR_NO_HUFF_TABLE, index);
 199
 200   if (! htbl->sent_table) {
 201     emit_marker(cinfo, M_DHT);
 202
 203     length = 0;
 204     for (i = 1; i <= 16; i++)
 205       length += htbl->bits[i];
 206
 207     emit_2bytes(cinfo, length + 2 + 1 + 16);
 208     emit_byte(cinfo, index);
 209
 210     for (i = 1; i <= 16; i++)
 211       emit_byte(cinfo, htbl->bits[i]);
 212
 213     for (i = 0; i < length; i++)
 214       emit_byte(cinfo, htbl->huffval[i]);
 215
 216     htbl->sent_table = TRUE;
 217   }
 218 }
 219
 220
 221 LOCAL(void)
 222 emit_dac (j_compress_ptr cinfo)
 223 /* Emit a DAC marker */
 224 /* Since the useful info is so small, we want to emit all the tables in */
 225 /* one DAC marker.  Therefore this routine does its own scan of the table. */
 226 {
 227 #ifdef C_ARITH_CODING_SUPPORTED
 228   char dc_in_use[NUM_ARITH_TBLS];
 229   char ac_in_use[NUM_ARITH_TBLS];
 230   int length, i;
 231   jpeg_component_info *compptr;
 232
 233   for (i = 0; i < NUM_ARITH_TBLS; i++)
 234     dc_in_use[i] = ac_in_use[i] = 0;
 235
 236   for (i = 0; i < cinfo->comps_in_scan; i++) {
 237     compptr = cinfo->cur_comp_info[i];
 238     dc_in_use[compptr->dc_tbl_no] = 1;
 239     ac_in_use[compptr->ac_tbl_no] = 1;
 240   }
 241
 242   length = 0;
 243   for (i = 0; i < NUM_ARITH_TBLS; i++)
 244     length += dc_in_use[i] + ac_in_use[i];
 245
 246   emit_marker(cinfo, M_DAC);
 247
 248   emit_2bytes(cinfo, length*2 + 2);
 249
 250   for (i = 0; i < NUM_ARITH_TBLS; i++) {
 251     if (dc_in_use[i]) {
 252       emit_byte(cinfo, i);
 253       emit_byte(cinfo, cinfo->arith_dc_L[i] + (cinfo->arith_dc_U[i]<<4));
 254     }
 255     if (ac_in_use[i]) {
 256       emit_byte(cinfo, i + 0x10);
 257       emit_byte(cinfo, cinfo->arith_ac_K[i]);
 258     }
 259   }
 260 #endif /* C_ARITH_CODING_SUPPORTED */
 261 }
 262
 263
 264 LOCAL(void)
 265 emit_dri (j_compress_ptr cinfo)
 266 /* Emit a DRI marker */
 267 {
 268   emit_marker(cinfo, M_DRI);
 269
 270   emit_2bytes(cinfo, 4);        /* fixed length */
 271
 272   emit_2bytes(cinfo, (int) cinfo->restart_interval);
 273 }
 274
 275
 276 LOCAL(void)
 277 emit_sof (j_compress_ptr cinfo, JPEG_MARKER code)
 278 /* Emit a SOF marker */
 279 {
 280   int ci;
 281   jpeg_component_info *compptr;
 282
 283   emit_marker(cinfo, code);
 284
 285   emit_2bytes(cinfo, 3 * cinfo->num_components + 2 + 5 + 1); /* length */
 286
 287   /* Make sure image isn't bigger than SOF field can handle */
 288   if ((long) cinfo->image_height > 65535L ||
 289       (long) cinfo->image_width > 65535L)
 290     ERREXIT1(cinfo, JERR_IMAGE_TOO_BIG, (unsigned int) 65535);
 291
 292   emit_byte(cinfo, cinfo->data_precision);
 293   emit_2bytes(cinfo, (int) cinfo->image_height);
 294   emit_2bytes(cinfo, (int) cinfo->image_width);
 295
 296   emit_byte(cinfo, cinfo->num_components);
 297
 298   for (ci = 0, compptr = cinfo->comp_info; ci < cinfo->num_components;
 299        ci++, compptr++) {
 300     emit_byte(cinfo, compptr->component_id);
 301     emit_byte(cinfo, (compptr->h_samp_factor << 4) + compptr->v_samp_factor);
 302     emit_byte(cinfo, compptr->quant_tbl_no);
 303   }
 304 }
 305
 306
 307 LOCAL(void)
 308 emit_sos (j_compress_ptr cinfo)
 309 /* Emit a SOS marker */
 310 {
 311   int i, td, ta;
 312   jpeg_component_info *compptr;
 313
 314   emit_marker(cinfo, M_SOS);
 315
 316   emit_2bytes(cinfo, 2 * cinfo->comps_in_scan + 2 + 1 + 3); /* length */
 317
 318   emit_byte(cinfo, cinfo->comps_in_scan);
 319
 320   for (i = 0; i < cinfo->comps_in_scan; i++) {
 321     compptr = cinfo->cur_comp_info[i];
 322     emit_byte(cinfo, compptr->component_id);
 323     td = compptr->dc_tbl_no;
 324     ta = compptr->ac_tbl_no;
 325     if (cinfo->progressive_mode) {
 326       /* Progressive mode: only DC or only AC tables are used in one scan;
 327        * furthermore, Huffman coding of DC refinement uses no table at all.
 328        * We emit 0 for unused field(s); this is recommended by the P&M text
 329        * but does not seem to be specified in the standard.
 330        */
 331       if (cinfo->Ss == 0) {
 332         ta = 0;                 /* DC scan */
 333         if (cinfo->Ah != 0 && !cinfo->arith_code)
 334           td = 0;               /* no DC table either */
 335       } else {
 336         td = 0;                 /* AC scan */
 337       }
 338     }
 339     emit_byte(cinfo, (td << 4) + ta);
 340   }
 341
 342   emit_byte(cinfo, cinfo->Ss);
 343   emit_byte(cinfo, cinfo->Se);
 344   emit_byte(cinfo, (cinfo->Ah << 4) + cinfo->Al);
 345 }
 346
 347
 348 LOCAL(void)
 349 emit_jfif_app0 (j_compress_ptr cinfo)
 350 /* Emit a JFIF-compliant APP0 marker */
 351 {
 352   /*
 353    * Length of APP0 block       (2 bytes)
 354    * Block ID                   (4 bytes - ASCII "JFIF")
 355    * Zero byte                  (1 byte to terminate the ID string)
 356    * Version Major, Minor       (2 bytes - major first)
 357    * Units                      (1 byte - 0x00 = none, 0x01 = inch, 0x02 = cm)
 358    * Xdpu                       (2 bytes - dots per unit horizontal)
 359    * Ydpu                       (2 bytes - dots per unit vertical)
 360    * Thumbnail X size           (1 byte)
 361    * Thumbnail Y size           (1 byte)
 362    */
 363
 364   emit_marker(cinfo, M_APP0);
 365
 366   emit_2bytes(cinfo, 2 + 4 + 1 + 2 + 1 + 2 + 2 + 1 + 1); /* length */
 367
 368   emit_byte(cinfo, 0x4A);       /* Identifier: ASCII "JFIF" */
 369   emit_byte(cinfo, 0x46);
 370   emit_byte(cinfo, 0x49);
 371   emit_byte(cinfo, 0x46);
 372   emit_byte(cinfo, 0);
 373   emit_byte(cinfo, cinfo->JFIF_major_version); /* Version fields */
 374   emit_byte(cinfo, cinfo->JFIF_minor_version);
 375   emit_byte(cinfo, cinfo->density_unit); /* Pixel size information */
 376   emit_2bytes(cinfo, (int) cinfo->X_density);
 377   emit_2bytes(cinfo, (int) cinfo->Y_density);
 378   emit_byte(cinfo, 0);          /* No thumbnail image */
 379   emit_byte(cinfo, 0);
 380 }
 381
 382
 383 LOCAL(void)
 384 emit_adobe_app14 (j_compress_ptr cinfo)
 385 /* Emit an Adobe APP14 marker */
 386 {
 387   /*
 388    * Length of APP14 block      (2 bytes)
 389    * Block ID                   (5 bytes - ASCII "Adobe")
 390    * Version Number             (2 bytes - currently 100)
 391    * Flags0                     (2 bytes - currently 0)
 392    * Flags1                     (2 bytes - currently 0)
 393    * Color transform            (1 byte)
 394    *
 395    * Although Adobe TN 5116 mentions Version = 101, all the Adobe files
 396    * now in circulation seem to use Version = 100, so that's what we write.
 397    *
 398    * We write the color transform byte as 1 if the JPEG color space is
 399    * YCbCr, 2 if it's YCCK, 0 otherwise.  Adobe's definition has to do with
 400    * whether the encoder performed a transformation, which is pretty useless.
 401    */
 402
 403   emit_marker(cinfo, M_APP14);
 404
 405   emit_2bytes(cinfo, 2 + 5 + 2 + 2 + 2 + 1); /* length */
 406
 407   emit_byte(cinfo, 0x41);       /* Identifier: ASCII "Adobe" */
 408   emit_byte(cinfo, 0x64);
 409   emit_byte(cinfo, 0x6F);
 410   emit_byte(cinfo, 0x62);
 411   emit_byte(cinfo, 0x65);
 412   emit_2bytes(cinfo, 100);      /* Version */
 413   emit_2bytes(cinfo, 0);        /* Flags0 */
 414   emit_2bytes(cinfo, 0);        /* Flags1 */
 415   switch (cinfo->jpeg_color_space) {
 416   case JCS_YCbCr:
 417     emit_byte(cinfo, 1);        /* Color transform = 1 */
 418     break;
 419   case JCS_YCCK:
 420     emit_byte(cinfo, 2);        /* Color transform = 2 */
 421     break;
 422   default:
 423     emit_byte(cinfo, 0);        /* Color transform = 0 */
 424     break;
 425   }
 426 }
 427
 428
 429 /*
 430  * These routines allow writing an arbitrary marker with parameters.
 431  * The only intended use is to emit COM or APPn markers after calling
 432  * write_file_header and before calling write_frame_header.
 433  * Other uses are not guaranteed to produce desirable results.
 434  * Counting the parameter bytes properly is the caller's responsibility.
 435  */
 436
 437 METHODDEF(void)
 438 write_marker_header (j_compress_ptr cinfo, int marker, unsigned int datalen)
 439 /* Emit an arbitrary marker header */
 440 {
 441   if (datalen > (unsigned int) 65533)           /* safety check */
 442     ERREXIT(cinfo, JERR_BAD_LENGTH);
 443
 444   emit_marker(cinfo, (JPEG_MARKER) marker);
 445
 446   emit_2bytes(cinfo, (int) (datalen + 2));      /* total length */
 447 }
 448
 449 METHODDEF(void)
 450 write_marker_byte (j_compress_ptr cinfo, int val)
 451 /* Emit one byte of marker parameters following write_marker_header */
 452 {
 453   emit_byte(cinfo, val);
 454 }
 455
 456
 457 /*
 458  * Write datastream header.
 459  * This consists of an SOI and optional APPn markers.
 460  * We recommend use of the JFIF marker, but not the Adobe marker,
 461  * when using YCbCr or grayscale data.  The JFIF marker should NOT
 462  * be used for any other JPEG colorspace.  The Adobe marker is helpful
 463  * to distinguish RGB, CMYK, and YCCK colorspaces.
 464  * Note that an application can write additional header markers after
 465  * jpeg_start_compress returns.
 466  */
 467
 468 METHODDEF(void)
 469 write_file_header (j_compress_ptr cinfo)
 470 {
 471   my_marker_ptr marker = (my_marker_ptr) cinfo->marker;
 472
 473   emit_marker(cinfo, M_SOI);    /* first the SOI */
 474
 475   /* SOI is defined to reset restart interval to 0 */
 476   marker->last_restart_interval = 0;
 477
 478   if (cinfo->write_JFIF_header) /* next an optional JFIF APP0 */
 479     emit_jfif_app0(cinfo);
 480   if (cinfo->write_Adobe_marker) /* next an optional Adobe APP14 */
 481     emit_adobe_app14(cinfo);
 482 }
 483
 484
 485 /*
 486  * Write frame header.
 487  * This consists of DQT and SOFn markers.
 488  * Note that we do not emit the SOF until we have emitted the DQT(s).
 489  * This avoids compatibility problems with incorrect implementations that
 490  * try to error-check the quant table numbers as soon as they see the SOF.
 491  */
 492
 493 METHODDEF(void)
 494 write_frame_header (j_compress_ptr cinfo)
 495 {
 496   int ci, prec;
 497   boolean is_baseline;
 498   jpeg_component_info *compptr;
 499
 500   /* Emit DQT for each quantization table.
 501    * Note that emit_dqt() suppresses any duplicate tables.
 502    */
 503   prec = 0;
 504   for (ci = 0, compptr = cinfo->comp_info; ci < cinfo->num_components;
 505        ci++, compptr++) {
 506     prec += emit_dqt(cinfo, compptr->quant_tbl_no);
 507   }
 508   /* now prec is nonzero iff there are any 16-bit quant tables. */
 509
 510   /* Check for a non-baseline specification.
 511    * Note we assume that Huffman table numbers won't be changed later.
 512    */
 513   if (cinfo->arith_code || cinfo->progressive_mode ||
 514       cinfo->data_precision != 8) {
 515     is_baseline = FALSE;
 516   } else {
 517     is_baseline = TRUE;
 518     for (ci = 0, compptr = cinfo->comp_info; ci < cinfo->num_components;
 519          ci++, compptr++) {
 520       if (compptr->dc_tbl_no > 1 || compptr->ac_tbl_no > 1)
 521         is_baseline = FALSE;
 522     }
 523     if (prec && is_baseline) {
 524       is_baseline = FALSE;
 525       /* If it's baseline except for quantizer size, warn the user */
 526       TRACEMS(cinfo, 0, JTRC_16BIT_TABLES);
 527     }
 528   }
 529
 530   /* Emit the proper SOF marker */
 531   if (cinfo->arith_code) {
 532     emit_sof(cinfo, M_SOF9);    /* SOF code for arithmetic coding */
 533   } else {
 534     if (cinfo->progressive_mode)
 535       emit_sof(cinfo, M_SOF2);  /* SOF code for progressive Huffman */
 536     else if (is_baseline)
 537       emit_sof(cinfo, M_SOF0);  /* SOF code for baseline implementation */
 538     else
 539       emit_sof(cinfo, M_SOF1);  /* SOF code for non-baseline Huffman file */
 540   }
 541 }
 542
 543
 544 /*
 545  * Write scan header.
 546  * This consists of DHT or DAC markers, optional DRI, and SOS.
 547  * Compressed data will be written following the SOS.
 548  */
 549
 550 METHODDEF(void)
 551 write_scan_header (j_compress_ptr cinfo)
 552 {
 553   my_marker_ptr marker = (my_marker_ptr) cinfo->marker;
 554   int i;
 555   jpeg_component_info *compptr;
 556
 557   if (cinfo->arith_code) {
 558     /* Emit arith conditioning info.  We may have some duplication
 559      * if the file has multiple scans, but it's so small it's hardly
 560      * worth worrying about.
 561      */
 562     emit_dac(cinfo);
 563   } else {
 564     /* Emit Huffman tables.
 565      * Note that emit_dht() suppresses any duplicate tables.
 566      */
 567     for (i = 0; i < cinfo->comps_in_scan; i++) {
 568       compptr = cinfo->cur_comp_info[i];
 569       if (cinfo->progressive_mode) {
 570         /* Progressive mode: only DC or only AC tables are used in one scan */
 571         if (cinfo->Ss == 0) {
 572           if (cinfo->Ah == 0)   /* DC needs no table for refinement scan */
 573             emit_dht(cinfo, compptr->dc_tbl_no, FALSE);
 574         } else {
 575           emit_dht(cinfo, compptr->ac_tbl_no, TRUE);
 576         }
 577       } else {
 578         /* Sequential mode: need both DC and AC tables */
 579         emit_dht(cinfo, compptr->dc_tbl_no, FALSE);
 580         emit_dht(cinfo, compptr->ac_tbl_no, TRUE);
 581       }
 582     }
 583   }
 584
 585   /* Emit DRI if required --- note that DRI value could change for each scan.
 586    * We avoid wasting space with unnecessary DRIs, however.
 587    */
 588   if (cinfo->restart_interval != marker->last_restart_interval) {
 589     emit_dri(cinfo);
 590     marker->last_restart_interval = cinfo->restart_interval;
 591   }
 592
 593   emit_sos(cinfo);
 594 }
 595
 596
 597 /*
 598  * Write datastream trailer.
 599  */
 600
 601 METHODDEF(void)
 602 write_file_trailer (j_compress_ptr cinfo)
 603 {
 604   emit_marker(cinfo, M_EOI);
 605 }
 606
 607
 608 /*
 609  * Write an abbreviated table-specification datastream.
 610  * This consists of SOI, DQT and DHT tables, and EOI.
 611  * Any table that is defined and not marked sent_table = TRUE will be
 612  * emitted.  Note that all tables will be marked sent_table = TRUE at exit.
 613  */
 614
 615 METHODDEF(void)
 616 write_tables_only (j_compress_ptr cinfo)
 617 {
 618   int i;
 619
 620   emit_marker(cinfo, M_SOI);
 621
 622   for (i = 0; i < NUM_QUANT_TBLS; i++) {
 623     if (cinfo->quant_tbl_ptrs[i] != NULL)
 624       (void) emit_dqt(cinfo, i);
 625   }
 626
 627   if (! cinfo->arith_code) {
 628     for (i = 0; i < NUM_HUFF_TBLS; i++) {
 629       if (cinfo->dc_huff_tbl_ptrs[i] != NULL)
 630         emit_dht(cinfo, i, FALSE);
 631       if (cinfo->ac_huff_tbl_ptrs[i] != NULL)
 632         emit_dht(cinfo, i, TRUE);
 633     }
 634   }
 635
 636   emit_marker(cinfo, M_EOI);
 637 }
 638
 639
 640 /*
 641  * Initialize the marker writer module.
 642  */
 643
 644 GLOBAL(void)
 645 jinit_marker_writer (j_compress_ptr cinfo)
 646 {
 647   my_marker_ptr marker;
 648
 649   /* Create the subobject */
 650   marker = (my_marker_ptr)
 651     (*cinfo->mem->alloc_small) ((j_common_ptr) cinfo, JPOOL_IMAGE,
 652                                 SIZEOF(my_marker_writer));
 653   cinfo->marker = (struct jpeg_marker_writer *) marker;
 654   /* Initialize method pointers */
 655   marker->pub.write_file_header = write_file_header;
 656   marker->pub.write_frame_header = write_frame_header;
 657   marker->pub.write_scan_header = write_scan_header;
 658   marker->pub.write_file_trailer = write_file_trailer;
 659   marker->pub.write_tables_only = write_tables_only;
 660   marker->pub.write_marker_header = write_marker_header;
 661   marker->pub.write_marker_byte = write_marker_byte;
 662   /* Initialize private state */
 663   marker->last_restart_interval = 0;
 664 }