jdmarker.c

Jpeg source code,jpeg编码解码示范

    for (buffp = 0; buffp < JFIF_LEN; buffp++)
      INPUT_BYTE(cinfo, b[buffp], return FALSE);
    length -= JFIF_LEN;

    if (b[0]==0x4A && b[1]==0x46 && b[2]==0x49 && b[3]==0x46 && b[4]==0) {
      /* Found JFIF APP0 marker: check version */
      /* Major version must be 1, anything else signals an incompatible change.
       * We used to treat this as an error, but now it's a nonfatal warning,
       * because some bozo at Hijaak couldn't read the spec.
       * Minor version should be 0..2, but process anyway if newer.
       */
      if (b[5] != 1)
	WARNMS2(cinfo, JWRN_JFIF_MAJOR, b[5], b[6]);
      else if (b[6] > 2)
	TRACEMS2(cinfo, 1, JTRC_JFIF_MINOR, b[5], b[6]);
      /* Save info */
      cinfo->saw_JFIF_marker = TRUE;
      cinfo->density_unit = b[7];
      cinfo->X_density = (b[8] << 8) + b[9];
      cinfo->Y_density = (b[10] << 8) + b[11];
      TRACEMS3(cinfo, 1, JTRC_JFIF,
	       cinfo->X_density, cinfo->Y_density, cinfo->density_unit);
      if (b[12] | b[13])
	TRACEMS2(cinfo, 1, JTRC_JFIF_THUMBNAIL, b[12], b[13]);
      if (length != ((INT32) b[12] * (INT32) b[13] * (INT32) 3))
	TRACEMS1(cinfo, 1, JTRC_JFIF_BADTHUMBNAILSIZE, (int) length);
    } else {
      /* Start of APP0 does not match "JFIF" */
      TRACEMS1(cinfo, 1, JTRC_APP0, (int) length + JFIF_LEN);
    }
  } else {
    /* Too short to be JFIF marker */
    TRACEMS1(cinfo, 1, JTRC_APP0, (int) length);
  }

  INPUT_SYNC(cinfo);
  if (length > 0)		/* skip any remaining data -- could be lots */
    (*cinfo->src->skip_input_data) (cinfo, (long) length);

  return TRUE;
}


METHODDEF(boolean)
get_app14 (j_decompress_ptr cinfo)
/* Process an APP14 marker */
{
#define ADOBE_LEN 12
  INT32 length;
  UINT8 b[ADOBE_LEN];
  int buffp;
  unsigned int version, flags0, flags1, transform;
  INPUT_VARS(cinfo);

  INPUT_2BYTES(cinfo, length, return FALSE);
  length -= 2;

  /* See if an Adobe APP14 marker is present */

  if (length >= ADOBE_LEN) {
    for (buffp = 0; buffp < ADOBE_LEN; buffp++)
      INPUT_BYTE(cinfo, b[buffp], return FALSE);
    length -= ADOBE_LEN;

    if (b[0]==0x41 && b[1]==0x64 && b[2]==0x6F && b[3]==0x62 && b[4]==0x65) {
      /* Found Adobe APP14 marker */
      version = (b[5] << 8) + b[6];
      flags0 = (b[7] << 8) + b[8];
      flags1 = (b[9] << 8) + b[10];
      transform = b[11];
      TRACEMS4(cinfo, 1, JTRC_ADOBE, version, flags0, flags1, transform);
      cinfo->saw_Adobe_marker = TRUE;
      cinfo->Adobe_transform = (UINT8) transform;
    } else {
      /* Start of APP14 does not match "Adobe" */
      TRACEMS1(cinfo, 1, JTRC_APP14, (int) length + ADOBE_LEN);
    }
  } else {
    /* Too short to be Adobe marker */
    TRACEMS1(cinfo, 1, JTRC_APP14, (int) length);
  }

  INPUT_SYNC(cinfo);
  if (length > 0)		/* skip any remaining data -- could be lots */
    (*cinfo->src->skip_input_data) (cinfo, (long) length);

  return TRUE;
}


LOCAL(boolean)
get_dac (j_decompress_ptr cinfo)
/* Process a DAC marker */
{
  INT32 length;
  int index, val;
  INPUT_VARS(cinfo);

  INPUT_2BYTES(cinfo, length, return FALSE);
  length -= 2;
  
  while (length > 0) {
    INPUT_BYTE(cinfo, index, return FALSE);
    INPUT_BYTE(cinfo, val, return FALSE);

    length -= 2;

    TRACEMS2(cinfo, 1, JTRC_DAC, index, val);

    if (index < 0 || index >= (2*NUM_ARITH_TBLS))
      ERREXIT1(cinfo, JERR_DAC_INDEX, index);

    if (index >= NUM_ARITH_TBLS) { /* define AC table */
      cinfo->arith_ac_K[index-NUM_ARITH_TBLS] = (UINT8) val;
    } else {			/* define DC table */
      cinfo->arith_dc_L[index] = (UINT8) (val & 0x0F);
      cinfo->arith_dc_U[index] = (UINT8) (val >> 4);
      if (cinfo->arith_dc_L[index] > cinfo->arith_dc_U[index])
	ERREXIT1(cinfo, JERR_DAC_VALUE, val);
    }
  }

  INPUT_SYNC(cinfo);
  return TRUE;
}


LOCAL(boolean)
get_dht (j_decompress_ptr cinfo)
/* Process a DHT marker */
{
  INT32 length;
  UINT8 bits[17];
  UINT8 huffval[256];
  int i, index, count;
  JHUFF_TBL **htblptr;
  INPUT_VARS(cinfo);

  INPUT_2BYTES(cinfo, length, return FALSE);
  length -= 2;
  
  while (length > 0) {
    INPUT_BYTE(cinfo, index, return FALSE);

    TRACEMS1(cinfo, 1, JTRC_DHT, index);
      
    bits[0] = 0;
    count = 0;
    for (i = 1; i <= 16; i++) {
      INPUT_BYTE(cinfo, bits[i], return FALSE);
      count += bits[i];
    }

    length -= 1 + 16;

    TRACEMS8(cinfo, 2, JTRC_HUFFBITS,
	     bits[1], bits[2], bits[3], bits[4],
	     bits[5], bits[6], bits[7], bits[8]);
    TRACEMS8(cinfo, 2, JTRC_HUFFBITS,
	     bits[9], bits[10], bits[11], bits[12],
	     bits[13], bits[14], bits[15], bits[16]);

    if (count > 256 || ((INT32) count) > length)
      ERREXIT(cinfo, JERR_DHT_COUNTS);

    for (i = 0; i < count; i++)
      INPUT_BYTE(cinfo, huffval[i], return FALSE);

    length -= count;

    if (index & 0x10) {		/* AC table definition */
      index -= 0x10;
      htblptr = &cinfo->ac_huff_tbl_ptrs[index];
    } else {			/* DC table definition */
      htblptr = &cinfo->dc_huff_tbl_ptrs[index];
    }

    if (index < 0 || index >= NUM_HUFF_TBLS)
      ERREXIT1(cinfo, JERR_DHT_INDEX, index);

    if (*htblptr == NULL)
      *htblptr = jpeg_alloc_huff_table((j_common_ptr) cinfo);
  
    MEMCOPY((*htblptr)->bits, bits, SIZEOF((*htblptr)->bits));
    MEMCOPY((*htblptr)->huffval, huffval, SIZEOF((*htblptr)->huffval));
  }

  INPUT_SYNC(cinfo);
  return TRUE;
}


LOCAL(boolean)
get_dqt (j_decompress_ptr cinfo)
/* Process a DQT marker */
{
  INT32 length;
  int n, i, prec;
  unsigned int tmp;
  JQUANT_TBL *quant_ptr;
  INPUT_VARS(cinfo);

  INPUT_2BYTES(cinfo, length, return FALSE);
  length -= 2;

  while (length > 0) {
    INPUT_BYTE(cinfo, n, return FALSE);
    prec = n >> 4;
    n &= 0x0F;

    TRACEMS2(cinfo, 1, JTRC_DQT, n, prec);

    if (n >= NUM_QUANT_TBLS)
      ERREXIT1(cinfo, JERR_DQT_INDEX, n);
      
    if (cinfo->quant_tbl_ptrs[n] == NULL)
      cinfo->quant_tbl_ptrs[n] = jpeg_alloc_quant_table((j_common_ptr) cinfo);
    quant_ptr = cinfo->quant_tbl_ptrs[n];

    for (i = 0; i < DCTSIZE2; i++) {
      if (prec)
	INPUT_2BYTES(cinfo, tmp, return FALSE);
      else
	INPUT_BYTE(cinfo, tmp, return FALSE);
      /* We convert the zigzag-order table to natural array order. */
      quant_ptr->quantval[jpeg_natural_order[i]] = (UINT16) tmp;
    }

    if (cinfo->err->trace_level >= 2) {
      for (i = 0; i < DCTSIZE2; i += 8) {
	TRACEMS8(cinfo, 2, JTRC_QUANTVALS,
		 quant_ptr->quantval[i],   quant_ptr->quantval[i+1],
		 quant_ptr->quantval[i+2], quant_ptr->quantval[i+3],
		 quant_ptr->quantval[i+4], quant_ptr->quantval[i+5],
		 quant_ptr->quantval[i+6], quant_ptr->quantval[i+7]);
      }
    }

    length -= DCTSIZE2+1;
    if (prec) length -= DCTSIZE2;
  }

  INPUT_SYNC(cinfo);
  return TRUE;
}


LOCAL(boolean)
get_dri (j_decompress_ptr cinfo)
/* Process a DRI marker */
{
  INT32 length;
  unsigned int tmp;
  INPUT_VARS(cinfo);

  INPUT_2BYTES(cinfo, length, return FALSE);
  
  if (length != 4)
    ERREXIT(cinfo, JERR_BAD_LENGTH);

  INPUT_2BYTES(cinfo, tmp, return FALSE);

  TRACEMS1(cinfo, 1, JTRC_DRI, tmp);

  cinfo->restart_interval = tmp;

  INPUT_SYNC(cinfo);
  return TRUE;
}


METHODDEF(boolean)
skip_variable (j_decompress_ptr cinfo)
/* Skip over an unknown or uninteresting variable-length marker */
{
  INT32 length;
  INPUT_VARS(cinfo);

  INPUT_2BYTES(cinfo, length, return FALSE);
  
  TRACEMS2(cinfo, 1, JTRC_MISC_MARKER, cinfo->unread_marker, (int) length);

  INPUT_SYNC(cinfo);		/* do before skip_input_data */
  (*cinfo->src->skip_input_data) (cinfo, (long) length - 2L);

  return TRUE;
}


/*
 * Find the next JPEG marker, save it in cinfo->unread_marker.
 * Returns FALSE if had to suspend before reaching a marker;
 * in that case cinfo->unread_marker is unchanged.
 *
 * Note that the result might not be a valid marker code,
 * but it will never be 0 or FF.
 */

LOCAL(boolean)
next_marker (j_decompress_ptr cinfo)
{
  int c;
  INPUT_VARS(cinfo);

  for (;;) {
    INPUT_BYTE(cinfo, c, return FALSE);
    /* Skip any non-FF bytes.
     * This may look a bit inefficient, but it will not occur in a valid file.
     * We sync after each discarded byte so that a suspending data source
     * can discard the byte from its buffer.
     */
    while (c != 0xFF) {
      cinfo->marker->discarded_bytes++;
      INPUT_SYNC(cinfo);
      INPUT_BYTE(cinfo, c, return FALSE);
    }
    /* This loop swallows any duplicate FF bytes.  Extra FFs are legal as
     * pad bytes, so don't count them in discarded_bytes.  We assume there
     * will not be so many consecutive FF bytes as to overflow a suspending
     * data source's input buffer.
     */
    do {
      INPUT_BYTE(cinfo, c, return FALSE);
    } while (c == 0xFF);
    if (c != 0)
      break;			/* found a valid marker, exit loop */
    /* Reach here if we found a stuffed-zero data sequence (FF/00).
     * Discard it and loop back to try again.
     */
    cinfo->marker->discarded_bytes += 2;
    INPUT_SYNC(cinfo);
  }

  if (cinfo->marker->discarded_bytes != 0) {
    WARNMS2(cinfo, JWRN_EXTRANEOUS_DATA, cinfo->marker->discarded_bytes, c);
    cinfo->marker->discarded_bytes = 0;
  }

  cinfo->unread_marker = c;

  INPUT_SYNC(cinfo);
  return TRUE;
}


LOCAL(boolean)
first_marker (j_decompress_ptr cinfo)
/* Like next_marker, but used to obtain the initial SOI marker. */
/* For this marker, we do not allow preceding garbage or fill; otherwise,
 * we might well scan an entire input file before realizing it ain't JPEG.
 * If an application wants to process non-JFIF files, it must seek to the
 * SOI before calling the JPEG library.