jcmarker.cpp File Reference

#include "jinclude.h"
#include "jpeglib.h"

Include dependency graph for jcmarker.cpp:

Classes
struct	my_marker_writer

Macros
#define	JPEG_INTERNALS

Typedefs
typedef my_marker_writer *	my_marker_ptr

Enumerations
enum	JPEG_MARKER {   M_SOF0 = 0xc0, M_SOF1 = 0xc1, M_SOF2 = 0xc2, M_SOF3 = 0xc3,   M_SOF5 = 0xc5, M_SOF6 = 0xc6, M_SOF7 = 0xc7, M_JPG = 0xc8,   M_SOF9 = 0xc9, M_SOF10 = 0xca, M_SOF11 = 0xcb, M_SOF13 = 0xcd,   M_SOF14 = 0xce, M_SOF15 = 0xcf, M_DHT = 0xc4, M_DAC = 0xcc,   M_RST0 = 0xd0, M_RST1 = 0xd1, M_RST2 = 0xd2, M_RST3 = 0xd3,   M_RST4 = 0xd4, M_RST5 = 0xd5, M_RST6 = 0xd6, M_RST7 = 0xd7,   M_SOI = 0xd8, M_EOI = 0xd9, M_SOS = 0xda, M_DQT = 0xdb,   M_DNL = 0xdc, M_DRI = 0xdd, M_DHP = 0xde, M_EXP = 0xdf,   M_APP0 = 0xe0, M_APP1 = 0xe1, M_APP2 = 0xe2, M_APP3 = 0xe3,   M_APP4 = 0xe4, M_APP5 = 0xe5, M_APP6 = 0xe6, M_APP7 = 0xe7,   M_APP8 = 0xe8, M_APP9 = 0xe9, M_APP10 = 0xea, M_APP11 = 0xeb,   M_APP12 = 0xec, M_APP13 = 0xed, M_APP14 = 0xee, M_APP15 = 0xef,   M_JPG0 = 0xf0, M_JPG13 = 0xfd, M_COM = 0xfe, M_TEM = 0x01,   M_ERROR = 0x100, M_SOF0 = 0xc0, M_SOF1 = 0xc1, M_SOF2 = 0xc2,   M_SOF3 = 0xc3, M_SOF5 = 0xc5, M_SOF6 = 0xc6, M_SOF7 = 0xc7,   M_JPG = 0xc8, M_SOF9 = 0xc9, M_SOF10 = 0xca, M_SOF11 = 0xcb,   M_SOF13 = 0xcd, M_SOF14 = 0xce, M_SOF15 = 0xcf, M_DHT = 0xc4,   M_DAC = 0xcc, M_RST0 = 0xd0, M_RST1 = 0xd1, M_RST2 = 0xd2,   M_RST3 = 0xd3, M_RST4 = 0xd4, M_RST5 = 0xd5, M_RST6 = 0xd6,   M_RST7 = 0xd7, M_SOI = 0xd8, M_EOI = 0xd9, M_SOS = 0xda,   M_DQT = 0xdb, M_DNL = 0xdc, M_DRI = 0xdd, M_DHP = 0xde,   M_EXP = 0xdf, M_APP0 = 0xe0, M_APP1 = 0xe1, M_APP2 = 0xe2,   M_APP3 = 0xe3, M_APP4 = 0xe4, M_APP5 = 0xe5, M_APP6 = 0xe6,   M_APP7 = 0xe7, M_APP8 = 0xe8, M_APP9 = 0xe9, M_APP10 = 0xea,   M_APP11 = 0xeb, M_APP12 = 0xec, M_APP13 = 0xed, M_APP14 = 0xee,   M_APP15 = 0xef, M_JPG0 = 0xf0, M_JPG13 = 0xfd, M_COM = 0xfe,   M_TEM = 0x01, M_ERROR = 0x100 }

Functions
static void	emit_byte (j_compress_ptr cinfo, int val)
static void	emit_marker (j_compress_ptr cinfo, JPEG_MARKER mark)
static void	emit_2bytes (j_compress_ptr cinfo, int value)
static int	emit_dqt (j_compress_ptr cinfo, int index)
static void	emit_dht (j_compress_ptr cinfo, int index, boolean is_ac)
static void	emit_dac (j_compress_ptr cinfo)
static void	emit_dri (j_compress_ptr cinfo)
static void	emit_sof (j_compress_ptr cinfo, JPEG_MARKER code)
static void	emit_sos (j_compress_ptr cinfo)
static void	emit_jfif_app0 (j_compress_ptr cinfo)
static void	emit_adobe_app14 (j_compress_ptr cinfo)
static void	write_marker_header (j_compress_ptr cinfo, int marker, unsigned int datalen)
static void	write_marker_byte (j_compress_ptr cinfo, int val)
static void	write_file_header (j_compress_ptr cinfo)
static void	write_frame_header (j_compress_ptr cinfo)
static void	write_scan_header (j_compress_ptr cinfo)
static void	write_file_trailer (j_compress_ptr cinfo)
static void	write_tables_only (j_compress_ptr cinfo)
void	jinit_marker_writer (j_compress_ptr cinfo)

Macro Definition Documentation

#define JPEG_INTERNALS

Typedef Documentation

typedef my_marker_writer* my_marker_ptr

Enumeration Type Documentation

enum JPEG_MARKER

Enumerator
M_SOF0
M_SOF1
M_SOF2
M_SOF3
M_SOF5
M_SOF6
M_SOF7
M_JPG
M_SOF9
M_SOF10
M_SOF11
M_SOF13
M_SOF14
M_SOF15
M_DHT
M_DAC
M_RST0
M_RST1
M_RST2
M_RST3
M_RST4
M_RST5
M_RST6
M_RST7
M_SOI
M_EOI
M_SOS
M_DQT
M_DNL
M_DRI
M_DHP
M_EXP
M_APP0
M_APP1
M_APP2
M_APP3
M_APP4
M_APP5
M_APP6
M_APP7
M_APP8
M_APP9
M_APP10
M_APP11
M_APP12
M_APP13
M_APP14
M_APP15
M_JPG0
M_JPG13
M_COM
M_TEM
M_ERROR
M_SOF0
M_SOF1
M_SOF2
M_SOF3
M_SOF5
M_SOF6
M_SOF7
M_JPG
M_SOF9
M_SOF10
M_SOF11
M_SOF13
M_SOF14
M_SOF15
M_DHT
M_DAC
M_RST0
M_RST1
M_RST2
M_RST3
M_RST4
M_RST5
M_RST6
M_RST7
M_SOI
M_EOI
M_SOS
M_DQT
M_DNL
M_DRI
M_DHP
M_EXP
M_APP0
M_APP1
M_APP2
M_APP3
M_APP4
M_APP5
M_APP6
M_APP7
M_APP8
M_APP9
M_APP10
M_APP11
M_APP12
M_APP13
M_APP14
M_APP15
M_JPG0
M_JPG13
M_COM
M_TEM
M_ERROR

             {          /* JPEG marker codes */
  M_SOF0  = 0xc0,
  M_SOF1  = 0xc1,
  M_SOF2  = 0xc2,
  M_SOF3  = 0xc3,
  
  M_SOF5  = 0xc5,
  M_SOF6  = 0xc6,
  M_SOF7  = 0xc7,
  
  M_JPG   = 0xc8,
  M_SOF9  = 0xc9,
  M_SOF10 = 0xca,
  M_SOF11 = 0xcb,
  
  M_SOF13 = 0xcd,
  M_SOF14 = 0xce,
  M_SOF15 = 0xcf,
  
  M_DHT   = 0xc4,
  
  M_DAC   = 0xcc,
  
  M_RST0  = 0xd0,
  M_RST1  = 0xd1,
  M_RST2  = 0xd2,
  M_RST3  = 0xd3,
  M_RST4  = 0xd4,
  M_RST5  = 0xd5,
  M_RST6  = 0xd6,
  M_RST7  = 0xd7,
  
  M_SOI   = 0xd8,
  M_EOI   = 0xd9,
  M_SOS   = 0xda,
  M_DQT   = 0xdb,
  M_DNL   = 0xdc,
  M_DRI   = 0xdd,
  M_DHP   = 0xde,
  M_EXP   = 0xdf,
  
  M_APP0  = 0xe0,
  M_APP1  = 0xe1,
  M_APP2  = 0xe2,
  M_APP3  = 0xe3,
  M_APP4  = 0xe4,
  M_APP5  = 0xe5,
  M_APP6  = 0xe6,
  M_APP7  = 0xe7,
  M_APP8  = 0xe8,
  M_APP9  = 0xe9,
  M_APP10 = 0xea,
  M_APP11 = 0xeb,
  M_APP12 = 0xec,
  M_APP13 = 0xed,
  M_APP14 = 0xee,
  M_APP15 = 0xef,
  
  M_JPG0  = 0xf0,
  M_JPG13 = 0xfd,
  M_COM   = 0xfe,
  
  M_TEM   = 0x01,
  
  M_ERROR = 0x100
} JPEG_MARKER;

Function Documentation

static void emit_byte ( j_compress_ptr  cinfo, int  val  )

static

{
  struct jpeg_destination_mgr * dest = cinfo->dest;

  *(dest->next_output_byte)++ = (JOCTET) val;
  if (--dest->free_in_buffer == 0) {
    if (! (*dest->empty_output_buffer) (cinfo))
      ERREXIT(cinfo, JERR_CANT_SUSPEND);
  }
}

static void emit_marker ( j_compress_ptr  cinfo, JPEG_MARKER  mark  )

static

{
  emit_byte(cinfo, 0xFF);
  emit_byte(cinfo, (int) mark);
}

static void emit_2bytes ( j_compress_ptr  cinfo, int  value  )

static

{
  emit_byte(cinfo, (value >> 8) & 0xFF);
  emit_byte(cinfo, value & 0xFF);
}

static int emit_dqt ( j_compress_ptr  cinfo, int  index  )

static

{
  JQUANT_TBL * qtbl = cinfo->quant_tbl_ptrs[index];
  int prec;
  int i;

  if (qtbl == NULL)
    ERREXIT1(cinfo, JERR_NO_QUANT_TABLE, index);

  prec = 0;
  for (i = 0; i < DCTSIZE2; i++) {
    if (qtbl->quantval[i] > 255)
      prec = 1;
  }

  if (! qtbl->sent_table) {
    emit_marker(cinfo, M_DQT);

    emit_2bytes(cinfo, prec ? DCTSIZE2*2 + 1 + 2 : DCTSIZE2 + 1 + 2);

    emit_byte(cinfo, index + (prec<<4));

    for (i = 0; i < DCTSIZE2; i++) {
      /* The table entries must be emitted in zigzag order. */
      unsigned int qval = qtbl->quantval[jpeg_natural_order[i]];
      if (prec)
    emit_byte(cinfo, (int) (qval >> 8));
      emit_byte(cinfo, (int) (qval & 0xFF));
    }

    qtbl->sent_table = TRUE;
  }

  return prec;
}

static void emit_dht ( j_compress_ptr  cinfo, int  index, boolean  is_ac  )

static

{
  JHUFF_TBL * htbl;
  int length, i;
  
  if (is_ac) {
    htbl = cinfo->ac_huff_tbl_ptrs[index];
    index += 0x10;      /* output index has AC bit set */
  } else {
    htbl = cinfo->dc_huff_tbl_ptrs[index];
  }

  if (htbl == NULL)
    ERREXIT1(cinfo, JERR_NO_HUFF_TABLE, index);
  
  if (! htbl->sent_table) {
    emit_marker(cinfo, M_DHT);
    
    length = 0;
    for (i = 1; i <= 16; i++)
      length += htbl->bits[i];
    
    emit_2bytes(cinfo, length + 2 + 1 + 16);
    emit_byte(cinfo, index);
    
    for (i = 1; i <= 16; i++)
      emit_byte(cinfo, htbl->bits[i]);
    
    for (i = 0; i < length; i++)
      emit_byte(cinfo, htbl->huffval[i]);
    
    htbl->sent_table = TRUE;
  }
}

static void emit_dac ( j_compress_ptr  cinfo )

static

{
#ifdef C_ARITH_CODING_SUPPORTED
  char dc_in_use[NUM_ARITH_TBLS];
  char ac_in_use[NUM_ARITH_TBLS];
  int length, i;
  jpeg_component_info *compptr;
  
  for (i = 0; i < NUM_ARITH_TBLS; i++)
    dc_in_use[i] = ac_in_use[i] = 0;
  
  for (i = 0; i < cinfo->comps_in_scan; i++) {
    compptr = cinfo->cur_comp_info[i];
    dc_in_use[compptr->dc_tbl_no] = 1;
    ac_in_use[compptr->ac_tbl_no] = 1;
  }
  
  length = 0;
  for (i = 0; i < NUM_ARITH_TBLS; i++)
    length += dc_in_use[i] + ac_in_use[i];
  
  emit_marker(cinfo, M_DAC);
  
  emit_2bytes(cinfo, length*2 + 2);
  
  for (i = 0; i < NUM_ARITH_TBLS; i++) {
    if (dc_in_use[i]) {
      emit_byte(cinfo, i);
      emit_byte(cinfo, cinfo->arith_dc_L[i] + (cinfo->arith_dc_U[i]<<4));
    }
    if (ac_in_use[i]) {
      emit_byte(cinfo, i + 0x10);
      emit_byte(cinfo, cinfo->arith_ac_K[i]);
    }
  }
#endif /* C_ARITH_CODING_SUPPORTED */
}

static void emit_dri ( j_compress_ptr  cinfo )

static

{
  emit_marker(cinfo, M_DRI);
  
  emit_2bytes(cinfo, 4);    /* fixed length */

  emit_2bytes(cinfo, (int) cinfo->restart_interval);
}

static void emit_sof ( j_compress_ptr  cinfo, JPEG_MARKER  code  )

static

{
  int ci;
  jpeg_component_info *compptr;
  
  emit_marker(cinfo, code);
  
  emit_2bytes(cinfo, 3 * cinfo->num_components + 2 + 5 + 1); /* length */

  /* Make sure image isn't bigger than SOF field can handle */
  if ((long) cinfo->image_height > 65535L ||
      (long) cinfo->image_width > 65535L)
    ERREXIT1(cinfo, JERR_IMAGE_TOO_BIG, (unsigned int) 65535);

  emit_byte(cinfo, cinfo->data_precision);
  emit_2bytes(cinfo, (int) cinfo->image_height);
  emit_2bytes(cinfo, (int) cinfo->image_width);

  emit_byte(cinfo, cinfo->num_components);

  for (ci = 0, compptr = cinfo->comp_info; ci < cinfo->num_components;
       ci++, compptr++) {
    emit_byte(cinfo, compptr->component_id);
    emit_byte(cinfo, (compptr->h_samp_factor << 4) + compptr->v_samp_factor);
    emit_byte(cinfo, compptr->quant_tbl_no);
  }
}

static void emit_sos ( j_compress_ptr  cinfo )

static

{
  int i, td, ta;
  jpeg_component_info *compptr;
  
  emit_marker(cinfo, M_SOS);
  
  emit_2bytes(cinfo, 2 * cinfo->comps_in_scan + 2 + 1 + 3); /* length */
  
  emit_byte(cinfo, cinfo->comps_in_scan);
  
  for (i = 0; i < cinfo->comps_in_scan; i++) {
    compptr = cinfo->cur_comp_info[i];
    emit_byte(cinfo, compptr->component_id);
    td = compptr->dc_tbl_no;
    ta = compptr->ac_tbl_no;
    if (cinfo->progressive_mode) {
      /* Progressive mode: only DC or only AC tables are used in one scan;
       * furthermore, Huffman coding of DC refinement uses no table at all.
       * We emit 0 for unused field(s); this is recommended by the P&M text
       * but does not seem to be specified in the standard.
       */
      if (cinfo->Ss == 0) {
    ta = 0;         /* DC scan */
    if (cinfo->Ah != 0 && !cinfo->arith_code)
      td = 0;       /* no DC table either */
      } else {
    td = 0;         /* AC scan */
      }
    }
    emit_byte(cinfo, (td << 4) + ta);
  }

  emit_byte(cinfo, cinfo->Ss);
  emit_byte(cinfo, cinfo->Se);
  emit_byte(cinfo, (cinfo->Ah << 4) + cinfo->Al);
}

static void emit_jfif_app0 ( j_compress_ptr  cinfo )

static

{
  /*
   * Length of APP0 block   (2 bytes)
   * Block ID           (4 bytes - ASCII "JFIF")
   * Zero byte          (1 byte to terminate the ID string)
   * Version Major, Minor   (2 bytes - major first)
   * Units          (1 byte - 0x00 = none, 0x01 = inch, 0x02 = cm)
   * Xdpu           (2 bytes - dots per unit horizontal)
   * Ydpu           (2 bytes - dots per unit vertical)
   * Thumbnail X size       (1 byte)
   * Thumbnail Y size       (1 byte)
   */
  
  emit_marker(cinfo, M_APP0);
  
  emit_2bytes(cinfo, 2 + 4 + 1 + 2 + 1 + 2 + 2 + 1 + 1); /* length */

  emit_byte(cinfo, 0x4A);   /* Identifier: ASCII "JFIF" */
  emit_byte(cinfo, 0x46);
  emit_byte(cinfo, 0x49);
  emit_byte(cinfo, 0x46);
  emit_byte(cinfo, 0);
  emit_byte(cinfo, cinfo->JFIF_major_version); /* Version fields */
  emit_byte(cinfo, cinfo->JFIF_minor_version);
  emit_byte(cinfo, cinfo->density_unit); /* Pixel size information */
  emit_2bytes(cinfo, (int) cinfo->X_density);
  emit_2bytes(cinfo, (int) cinfo->Y_density);
  emit_byte(cinfo, 0);      /* No thumbnail image */
  emit_byte(cinfo, 0);
}

static void emit_adobe_app14 ( j_compress_ptr  cinfo )

static

{
  /*
   * Length of APP14 block  (2 bytes)
   * Block ID           (5 bytes - ASCII "Adobe")
   * Version Number     (2 bytes - currently 100)
   * Flags0         (2 bytes - currently 0)
   * Flags1         (2 bytes - currently 0)
   * Color transform        (1 byte)
   *
   * Although Adobe TN 5116 mentions Version = 101, all the Adobe files
   * now in circulation seem to use Version = 100, so that's what we write.
   *
   * We write the color transform byte as 1 if the JPEG color space is
   * YCbCr, 2 if it's YCCK, 0 otherwise.  Adobe's definition has to do with
   * whether the encoder performed a transformation, which is pretty useless.
   */
  
  emit_marker(cinfo, M_APP14);
  
  emit_2bytes(cinfo, 2 + 5 + 2 + 2 + 2 + 1); /* length */

  emit_byte(cinfo, 0x41);   /* Identifier: ASCII "Adobe" */
  emit_byte(cinfo, 0x64);
  emit_byte(cinfo, 0x6F);
  emit_byte(cinfo, 0x62);
  emit_byte(cinfo, 0x65);
  emit_2bytes(cinfo, 100);  /* Version */
  emit_2bytes(cinfo, 0);    /* Flags0 */
  emit_2bytes(cinfo, 0);    /* Flags1 */
  switch (cinfo->jpeg_color_space) {
  case JCS_YCbCr:
    emit_byte(cinfo, 1);    /* Color transform = 1 */
    break;
  case JCS_YCCK:
    emit_byte(cinfo, 2);    /* Color transform = 2 */
    break;
  default:
    emit_byte(cinfo, 0);    /* Color transform = 0 */
    break;
  }
}

static void write_marker_header ( j_compress_ptr  cinfo, int  marker, unsigned int  datalen  )

static

{
  if (datalen > (unsigned int) 65533)       /* safety check */
    ERREXIT(cinfo, JERR_BAD_LENGTH);

  emit_marker(cinfo, (JPEG_MARKER) marker);

  emit_2bytes(cinfo, (int) (datalen + 2));  /* total length */
}

static void write_marker_byte ( j_compress_ptr  cinfo, int  val  )

static

{
  emit_byte(cinfo, val);
}

static void write_file_header ( j_compress_ptr  cinfo )

static

{
  my_marker_ptr marker = (my_marker_ptr) cinfo->marker;

  emit_marker(cinfo, M_SOI);    /* first the SOI */

  /* SOI is defined to reset restart interval to 0 */
  marker->last_restart_interval = 0;

  if (cinfo->write_JFIF_header) /* next an optional JFIF APP0 */
    emit_jfif_app0(cinfo);
  if (cinfo->write_Adobe_marker) /* next an optional Adobe APP14 */
    emit_adobe_app14(cinfo);
}

static void write_frame_header ( j_compress_ptr  cinfo )

static

{
  int ci, prec;
  boolean is_baseline;
  jpeg_component_info *compptr;
  
  /* Emit DQT for each quantization table.
   * Note that emit_dqt() suppresses any duplicate tables.
   */
  prec = 0;
  for (ci = 0, compptr = cinfo->comp_info; ci < cinfo->num_components;
       ci++, compptr++) {
    prec += emit_dqt(cinfo, compptr->quant_tbl_no);
  }
  /* now prec is nonzero iff there are any 16-bit quant tables. */

  /* Check for a non-baseline specification.
   * Note we assume that Huffman table numbers won't be changed later.
   */
  if (cinfo->arith_code || cinfo->progressive_mode ||
      cinfo->data_precision != 8) {
    is_baseline = FALSE;
  } else {
    is_baseline = TRUE;
    for (ci = 0, compptr = cinfo->comp_info; ci < cinfo->num_components;
     ci++, compptr++) {
      if (compptr->dc_tbl_no > 1 || compptr->ac_tbl_no > 1)
    is_baseline = FALSE;
    }
    if (prec && is_baseline) {
      is_baseline = FALSE;
      /* If it's baseline except for quantizer size, warn the user */
      TRACEMS(cinfo, 0, JTRC_16BIT_TABLES);
    }
  }

  /* Emit the proper SOF marker */
  if (cinfo->arith_code) {
    emit_sof(cinfo, M_SOF9);    /* SOF code for arithmetic coding */
  } else {
    if (cinfo->progressive_mode)
      emit_sof(cinfo, M_SOF2);  /* SOF code for progressive Huffman */
    else if (is_baseline)
      emit_sof(cinfo, M_SOF0);  /* SOF code for baseline implementation */
    else
      emit_sof(cinfo, M_SOF1);  /* SOF code for non-baseline Huffman file */
  }
}

static void write_scan_header ( j_compress_ptr  cinfo )

static

{
  my_marker_ptr marker = (my_marker_ptr) cinfo->marker;
  int i;
  jpeg_component_info *compptr;

  if (cinfo->arith_code) {
    /* Emit arith conditioning info.  We may have some duplication
     * if the file has multiple scans, but it's so small it's hardly
     * worth worrying about.
     */
    emit_dac(cinfo);
  } else {
    /* Emit Huffman tables.
     * Note that emit_dht() suppresses any duplicate tables.
     */
    for (i = 0; i < cinfo->comps_in_scan; i++) {
      compptr = cinfo->cur_comp_info[i];
      if (cinfo->progressive_mode) {
    /* Progressive mode: only DC or only AC tables are used in one scan */
    if (cinfo->Ss == 0) {
      if (cinfo->Ah == 0)   /* DC needs no table for refinement scan */
        emit_dht(cinfo, compptr->dc_tbl_no, FALSE);
    } else {
      emit_dht(cinfo, compptr->ac_tbl_no, TRUE);
    }
      } else {
    /* Sequential mode: need both DC and AC tables */
    emit_dht(cinfo, compptr->dc_tbl_no, FALSE);
    emit_dht(cinfo, compptr->ac_tbl_no, TRUE);
      }
    }
  }

  /* Emit DRI if required --- note that DRI value could change for each scan.
   * We avoid wasting space with unnecessary DRIs, however.
   */
  if (cinfo->restart_interval != marker->last_restart_interval) {
    emit_dri(cinfo);
    marker->last_restart_interval = cinfo->restart_interval;
  }

  emit_sos(cinfo);
}

static void write_file_trailer ( j_compress_ptr  cinfo )

static

{
  emit_marker(cinfo, M_EOI);
}

static void write_tables_only ( j_compress_ptr  cinfo )

static

{
  int i;

  emit_marker(cinfo, M_SOI);

  for (i = 0; i < NUM_QUANT_TBLS; i++) {
    if (cinfo->quant_tbl_ptrs[i] != NULL)
      (void) emit_dqt(cinfo, i);
  }

  if (! cinfo->arith_code) {
    for (i = 0; i < NUM_HUFF_TBLS; i++) {
      if (cinfo->dc_huff_tbl_ptrs[i] != NULL)
    emit_dht(cinfo, i, FALSE);
      if (cinfo->ac_huff_tbl_ptrs[i] != NULL)
    emit_dht(cinfo, i, TRUE);
    }
  }

  emit_marker(cinfo, M_EOI);
}

void jinit_marker_writer

(

j_compress_ptr

cinfo

)

{
  my_marker_ptr marker;

  /* Create the subobject */
  marker = (my_marker_ptr)
    (*cinfo->mem->alloc_small) ((j_common_ptr) cinfo, JPOOL_IMAGE,
                SIZEOF(my_marker_writer));
  cinfo->marker = (struct jpeg_marker_writer *) marker;
  /* Initialize method pointers */
  marker->pub.write_file_header = write_file_header;
  marker->pub.write_frame_header = write_frame_header;
  marker->pub.write_scan_header = write_scan_header;
  marker->pub.write_file_trailer = write_file_trailer;
  marker->pub.write_tables_only = write_tables_only;
  marker->pub.write_marker_header = write_marker_header;
  marker->pub.write_marker_byte = write_marker_byte;
  /* Initialize private state */
  marker->last_restart_interval = 0;
}