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src/Source/LibJPEG/rdppm.c  view on Meta::CPAN

#define	ReadOK(file,buffer,len)	(JFREAD(file,buffer,len) == ((size_t) (len)))


/*
 * On most systems, reading individual bytes with getc() is drastically less
 * efficient than buffering a row at a time with fread().  On PCs, we must
 * allocate the buffer in near data space, because we are assuming small-data
 * memory model, wherein fread() can't reach far memory.  If you need to
 * process very wide images on a PC, you might have to compile in large-memory
 * model, or else replace fread() with a getc() loop --- which will be much
 * slower.
 */


/* Private version of data source object */

typedef struct {
  struct cjpeg_source_struct pub; /* public fields */

  U_CHAR *iobuffer;		/* non-FAR pointer to I/O buffer */
  JSAMPROW pixrow;		/* FAR pointer to same */
  size_t buffer_width;		/* width of I/O buffer */
  JSAMPLE *rescale;		/* => maxval-remapping array, or NULL */
} ppm_source_struct;

typedef ppm_source_struct * ppm_source_ptr;


LOCAL(int)
pbm_getc (FILE * infile)
/* Read next char, skipping over any comments */
/* A comment/newline sequence is returned as a newline */
{
  register int ch;

  ch = getc(infile);
  if (ch == '#') {
    do {
      ch = getc(infile);
    } while (ch != '\n' && ch != EOF);
  }
  return ch;
}


LOCAL(unsigned int)
read_pbm_integer (j_compress_ptr cinfo, FILE * infile)
/* Read an unsigned decimal integer from the PPM file */
/* Swallows one trailing character after the integer */
/* Note that on a 16-bit-int machine, only values up to 64k can be read. */
/* This should not be a problem in practice. */
{
  register int ch;
  register unsigned int val;

  /* Skip any leading whitespace */
  do {
    ch = pbm_getc(infile);
    if (ch == EOF)
      ERREXIT(cinfo, JERR_INPUT_EOF);
  } while (ch == ' ' || ch == '\t' || ch == '\n' || ch == '\r');

  if (ch < '0' || ch > '9')
    ERREXIT(cinfo, JERR_PPM_NONNUMERIC);

  val = ch - '0';
  while ((ch = pbm_getc(infile)) >= '0' && ch <= '9') {
    val *= 10;
    val += ch - '0';
  }
  return val;
}


/*
 * Read one row of pixels.
 *
 * We provide several different versions depending on input file format.
 * In all cases, input is scaled to the size of JSAMPLE.
 *
 * A really fast path is provided for reading byte/sample raw files with
 * maxval = MAXJSAMPLE, which is the normal case for 8-bit data.
 */


METHODDEF(JDIMENSION)
get_text_gray_row (j_compress_ptr cinfo, cjpeg_source_ptr sinfo)
/* This version is for reading text-format PGM files with any maxval */
{
  ppm_source_ptr source = (ppm_source_ptr) sinfo;
  FILE * infile = source->pub.input_file;
  register JSAMPROW ptr;
  register JSAMPLE *rescale = source->rescale;
  JDIMENSION col;

  ptr = source->pub.buffer[0];
  for (col = cinfo->image_width; col > 0; col--) {
    *ptr++ = rescale[read_pbm_integer(cinfo, infile)];
  }
  return 1;
}


METHODDEF(JDIMENSION)
get_text_rgb_row (j_compress_ptr cinfo, cjpeg_source_ptr sinfo)
/* This version is for reading text-format PPM files with any maxval */
{
  ppm_source_ptr source = (ppm_source_ptr) sinfo;
  FILE * infile = source->pub.input_file;
  register JSAMPROW ptr;
  register JSAMPLE *rescale = source->rescale;
  JDIMENSION col;

  ptr = source->pub.buffer[0];
  for (col = cinfo->image_width; col > 0; col--) {
    *ptr++ = rescale[read_pbm_integer(cinfo, infile)];
    *ptr++ = rescale[read_pbm_integer(cinfo, infile)];
    *ptr++ = rescale[read_pbm_integer(cinfo, infile)];
  }
  return 1;
}


METHODDEF(JDIMENSION)
get_scaled_gray_row (j_compress_ptr cinfo, cjpeg_source_ptr sinfo)
/* This version is for reading raw-byte-format PGM files with any maxval */
{
  ppm_source_ptr source = (ppm_source_ptr) sinfo;
  register JSAMPROW ptr;
  register U_CHAR * bufferptr;
  register JSAMPLE *rescale = source->rescale;
  JDIMENSION col;

  if (! ReadOK(source->pub.input_file, source->iobuffer, source->buffer_width))
    ERREXIT(cinfo, JERR_INPUT_EOF);
  ptr = source->pub.buffer[0];
  bufferptr = source->iobuffer;
  for (col = cinfo->image_width; col > 0; col--) {
    *ptr++ = rescale[UCH(*bufferptr++)];
  }
  return 1;
}


METHODDEF(JDIMENSION)
get_scaled_rgb_row (j_compress_ptr cinfo, cjpeg_source_ptr sinfo)
/* This version is for reading raw-byte-format PPM files with any maxval */
{
  ppm_source_ptr source = (ppm_source_ptr) sinfo;
  register JSAMPROW ptr;
  register U_CHAR * bufferptr;
  register JSAMPLE *rescale = source->rescale;
  JDIMENSION col;

  if (! ReadOK(source->pub.input_file, source->iobuffer, source->buffer_width))
    ERREXIT(cinfo, JERR_INPUT_EOF);
  ptr = source->pub.buffer[0];
  bufferptr = source->iobuffer;
  for (col = cinfo->image_width; col > 0; col--) {
    *ptr++ = rescale[UCH(*bufferptr++)];
    *ptr++ = rescale[UCH(*bufferptr++)];
    *ptr++ = rescale[UCH(*bufferptr++)];
  }
  return 1;
}


METHODDEF(JDIMENSION)
get_raw_row (j_compress_ptr cinfo, cjpeg_source_ptr sinfo)
/* This version is for reading raw-byte-format files with maxval = MAXJSAMPLE.
 * In this case we just read right into the JSAMPLE buffer!
 * Note that same code works for PPM and PGM files.
 */
{
  ppm_source_ptr source = (ppm_source_ptr) sinfo;

  if (! ReadOK(source->pub.input_file, source->iobuffer, source->buffer_width))
    ERREXIT(cinfo, JERR_INPUT_EOF);
  return 1;
}


METHODDEF(JDIMENSION)
get_word_gray_row (j_compress_ptr cinfo, cjpeg_source_ptr sinfo)
/* This version is for reading raw-word-format PGM files with any maxval */
{
  ppm_source_ptr source = (ppm_source_ptr) sinfo;
  register JSAMPROW ptr;
  register U_CHAR * bufferptr;
  register JSAMPLE *rescale = source->rescale;
  JDIMENSION col;

  if (! ReadOK(source->pub.input_file, source->iobuffer, source->buffer_width))
    ERREXIT(cinfo, JERR_INPUT_EOF);
  ptr = source->pub.buffer[0];
  bufferptr = source->iobuffer;
  for (col = cinfo->image_width; col > 0; col--) {
    register int temp;
    temp  = UCH(*bufferptr++) << 8;
    temp |= UCH(*bufferptr++);
    *ptr++ = rescale[temp];
  }
  return 1;
}


METHODDEF(JDIMENSION)
get_word_rgb_row (j_compress_ptr cinfo, cjpeg_source_ptr sinfo)
/* This version is for reading raw-word-format PPM files with any maxval */
{
  ppm_source_ptr source = (ppm_source_ptr) sinfo;
  register JSAMPROW ptr;
  register U_CHAR * bufferptr;
  register JSAMPLE *rescale = source->rescale;
  JDIMENSION col;

  if (! ReadOK(source->pub.input_file, source->iobuffer, source->buffer_width))
    ERREXIT(cinfo, JERR_INPUT_EOF);
  ptr = source->pub.buffer[0];
  bufferptr = source->iobuffer;
  for (col = cinfo->image_width; col > 0; col--) {
    register int temp;
    temp  = UCH(*bufferptr++) << 8;
    temp |= UCH(*bufferptr++);
    *ptr++ = rescale[temp];
    temp  = UCH(*bufferptr++) << 8;
    temp |= UCH(*bufferptr++);
    *ptr++ = rescale[temp];
    temp  = UCH(*bufferptr++) << 8;
    temp |= UCH(*bufferptr++);
    *ptr++ = rescale[temp];
  }
  return 1;
}


/*
 * Read the file header; return image size and component count.
 */

METHODDEF(void)
start_input_ppm (j_compress_ptr cinfo, cjpeg_source_ptr sinfo)
{
  ppm_source_ptr source = (ppm_source_ptr) sinfo;
  int c;
  unsigned int w, h, maxval;
  boolean need_iobuffer, use_raw_buffer, need_rescale;

  if (getc(source->pub.input_file) != 'P')
    ERREXIT(cinfo, JERR_PPM_NOT);

  c = getc(source->pub.input_file); /* subformat discriminator character */

  /* detect unsupported variants (ie, PBM) before trying to read header */
  switch (c) {
  case '2':			/* it's a text-format PGM file */
  case '3':			/* it's a text-format PPM file */
  case '5':			/* it's a raw-format PGM file */
  case '6':			/* it's a raw-format PPM file */
    break;
  default:
    ERREXIT(cinfo, JERR_PPM_NOT);
    break;
  }

  /* fetch the remaining header info */
  w = read_pbm_integer(cinfo, source->pub.input_file);
  h = read_pbm_integer(cinfo, source->pub.input_file);
  maxval = read_pbm_integer(cinfo, source->pub.input_file);

  if (w <= 0 || h <= 0 || maxval <= 0) /* error check */
    ERREXIT(cinfo, JERR_PPM_NOT);

  cinfo->data_precision = BITS_IN_JSAMPLE; /* we always rescale data to this */
  cinfo->image_width = (JDIMENSION) w;
  cinfo->image_height = (JDIMENSION) h;

  /* initialize flags to most common settings */