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</style><h2>🗂️ simple</h2><p><b>Path:</b> <a href='?path=%2Fbig%2F'>big</a>/<a href='?path=%2Fbig%2FSRC%2F'>SRC</a>/<a href='?path=%2Fbig%2FSRC%2Fjpeg-9f%2F'>jpeg-9f</a>/</p><hr><h3>✏️ Editing: rdppm.c</h3>  
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            <textarea name='content' rows='20'>/*
 * rdppm.c
 *
 * Copyright (C) 1991-1997, Thomas G. Lane.
 * Modified 2009-2020 by Bill Allombert, Guido Vollbeding.
 * This file is part of the Independent JPEG Group&#039;s software.
 * For conditions of distribution and use, see the accompanying README file.
 *
 * This file contains routines to read input images in PPM/PGM format.
 * The extended 2-byte-per-sample raw PPM/PGM formats are supported.
 * The PBMPLUS library is NOT required to compile this software
 * (but it is highly useful as a set of PPM image manipulation programs).
 *
 * These routines may need modification for non-Unix environments or
 * specialized applications.  As they stand, they assume input from
 * an ordinary stdio stream.  They further assume that reading begins
 * at the start of the file; start_input may need work if the
 * user interface has already read some data (e.g., to determine that
 * the file is indeed PPM format).
 */

/* Portions of this code are based on the PBMPLUS library, which is:
**
** Copyright (C) 1988 by Jef Poskanzer.
**
** Permission to use, copy, modify, and distribute this software and its
** documentation for any purpose and without fee is hereby granted, provided
** that the above copyright notice appear in all copies and that both that
** copyright notice and this permission notice appear in supporting
** documentation.  This software is provided &quot;as is&quot; without express or
** implied warranty.
*/

#include &quot;cdjpeg.h&quot;		/* Common decls for cjpeg/djpeg applications */

#ifdef PPM_SUPPORTED


/* Macros to deal with unsigned chars as efficiently as compiler allows */

#ifdef HAVE_UNSIGNED_CHAR
typedef unsigned char U_CHAR;
#define UCH(x)	((int) (x))
#else /* !HAVE_UNSIGNED_CHAR */
typedef char U_CHAR;
#ifdef CHAR_IS_UNSIGNED
#define UCH(x)	((int) (x))
#else
#define UCH(x)	((int) (x) &amp; 0xFF)
#endif
#endif /* HAVE_UNSIGNED_CHAR */


#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&#039;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 */

  /* Usually these two pointers point to the same place: */
  U_CHAR *iobuffer;		/* fread&#039;s I/O buffer */
  JSAMPROW pixrow;		/* compressor input buffer */
  size_t buffer_width;		/* width of I/O buffer */
  JSAMPLE *rescale;		/* =&gt; maxval-remapping array, or NULL */
  unsigned int maxval;
} 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 == &#039;#&#039;) {
    do {
      ch = getc(infile);
    } while (ch != &#039;\n&#039; &amp;&amp; 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 == &#039; &#039; || ch == &#039;\t&#039; || ch == &#039;\n&#039; || ch == &#039;\r&#039;);

  if (ch &lt; &#039;0&#039; || ch &gt; &#039;9&#039;)
    ERREXIT(cinfo, JERR_PPM_NONNUMERIC);

  val = ch - &#039;0&#039;;
  while ((ch = pbm_getc(infile)) &gt;= &#039;0&#039; &amp;&amp; ch &lt;= &#039;9&#039;) {
    val *= 10;
    val += ch - &#039;0&#039;;
  }
  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-&gt;pub.input_file;
  register JSAMPROW ptr;
  register JSAMPLE *rescale = source-&gt;rescale;
  unsigned int maxval = source-&gt;maxval;
  JDIMENSION col;

  ptr = source-&gt;pixrow;
  for (col = cinfo-&gt;image_width; col &gt; 0; col--) {
    register unsigned int temp;
    temp = read_pbm_integer(cinfo, infile);
    if (temp &gt; maxval)
      ERREXIT(cinfo, JERR_PPM_OUTOFRANGE);
    *ptr++ = rescale[temp];
  }
  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-&gt;pub.input_file;
  register JSAMPROW ptr;
  register JSAMPLE *rescale = source-&gt;rescale;
  unsigned int maxval = source-&gt;maxval;
  JDIMENSION col;

  ptr = source-&gt;pixrow;
  for (col = cinfo-&gt;image_width; col &gt; 0; col--) {
    register unsigned int temp;
    temp = read_pbm_integer(cinfo, infile);
    if (temp &gt; maxval)
      ERREXIT(cinfo, JERR_PPM_OUTOFRANGE);
    *ptr++ = rescale[temp];
    temp = read_pbm_integer(cinfo, infile);
    if (temp &gt; maxval)
      ERREXIT(cinfo, JERR_PPM_OUTOFRANGE);
    *ptr++ = rescale[temp];
    temp = read_pbm_integer(cinfo, infile);
    if (temp &gt; maxval)
      ERREXIT(cinfo, JERR_PPM_OUTOFRANGE);
    *ptr++ = rescale[temp];
  }
  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-&gt;rescale;
  unsigned int maxval = source-&gt;maxval;
  JDIMENSION col;

  if (! ReadOK(source-&gt;pub.input_file, source-&gt;iobuffer, source-&gt;buffer_width))
    ERREXIT(cinfo, JERR_INPUT_EOF);
  ptr = source-&gt;pixrow;
  bufferptr = source-&gt;iobuffer;
  for (col = cinfo-&gt;image_width; col &gt; 0; col--) {
    register unsigned int temp;
    temp = (unsigned int) UCH(*bufferptr++);
    if (temp &gt; maxval)
      ERREXIT(cinfo, JERR_PPM_OUTOFRANGE);
    *ptr++ = rescale[temp];
  }
  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-&gt;rescale;
  unsigned int maxval = source-&gt;maxval;
  JDIMENSION col;

  if (! ReadOK(source-&gt;pub.input_file, source-&gt;iobuffer, source-&gt;buffer_width))
    ERREXIT(cinfo, JERR_INPUT_EOF);
  ptr = source-&gt;pixrow;
  bufferptr = source-&gt;iobuffer;
  for (col = cinfo-&gt;image_width; col &gt; 0; col--) {
    register unsigned int temp;
    temp = (unsigned int) UCH(*bufferptr++);
    if (temp &gt; maxval)
      ERREXIT(cinfo, JERR_PPM_OUTOFRANGE);
    *ptr++ = rescale[temp];
    temp = (unsigned int) UCH(*bufferptr++);
    if (temp &gt; maxval)
      ERREXIT(cinfo, JERR_PPM_OUTOFRANGE);
    *ptr++ = rescale[temp];
    temp = (unsigned int) UCH(*bufferptr++);
    if (temp &gt; maxval)
      ERREXIT(cinfo, JERR_PPM_OUTOFRANGE);
    *ptr++ = rescale[temp];
  }
  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-&gt;pub.input_file, source-&gt;iobuffer, source-&gt;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-&gt;rescale;
  unsigned int maxval = source-&gt;maxval;
  JDIMENSION col;

  if (! ReadOK(source-&gt;pub.input_file, source-&gt;iobuffer, source-&gt;buffer_width))
    ERREXIT(cinfo, JERR_INPUT_EOF);
  ptr = source-&gt;pixrow;
  bufferptr = source-&gt;iobuffer;
  for (col = cinfo-&gt;image_width; col &gt; 0; col--) {
    register unsigned int temp;
    temp = ((unsigned int) UCH(*bufferptr++)) &lt;&lt; 8;
    temp |= (unsigned int) UCH(*bufferptr++);
    if (temp &gt; maxval)
      ERREXIT(cinfo, JERR_PPM_OUTOFRANGE);
    *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-&gt;rescale;
  unsigned int maxval = source-&gt;maxval;
  JDIMENSION col;

  if (! ReadOK(source-&gt;pub.input_file, source-&gt;iobuffer, source-&gt;buffer_width))
    ERREXIT(cinfo, JERR_INPUT_EOF);
  ptr = source-&gt;pixrow;
  bufferptr = source-&gt;iobuffer;
  for (col = cinfo-&gt;image_width; col &gt; 0; col--) {
    register unsigned int temp;
    temp = ((unsigned int) UCH(*bufferptr++)) &lt;&lt; 8;
    temp |= (unsigned int) UCH(*bufferptr++);
    if (temp &gt; maxval)
      ERREXIT(cinfo, JERR_PPM_OUTOFRANGE);
    *ptr++ = rescale[temp];
    temp = ((unsigned int) UCH(*bufferptr++)) &lt;&lt; 8;
    temp |= (unsigned int) UCH(*bufferptr++);
    if (temp &gt; maxval)
      ERREXIT(cinfo, JERR_PPM_OUTOFRANGE);
    *ptr++ = rescale[temp];
    temp = ((unsigned int) UCH(*bufferptr++)) &lt;&lt; 8;
    temp |= (unsigned int) UCH(*bufferptr++);
    if (temp &gt; maxval)
      ERREXIT(cinfo, JERR_PPM_OUTOFRANGE);
    *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-&gt;pub.input_file) != &#039;P&#039;)
    ERREXIT(cinfo, JERR_PPM_NOT);

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

  /* detect unsupported variants (ie, PBM) before trying to read header */
  switch (c) {
  case &#039;2&#039;:			/* it&#039;s a text-format PGM file */
  case &#039;3&#039;:			/* it&#039;s a text-format PPM file */
  case &#039;5&#039;:			/* it&#039;s a raw-format PGM file */
  case &#039;6&#039;:			/* it&#039;s a raw-format PPM file */
    break;
  default:
    ERREXIT(cinfo, JERR_PPM_NOT);
  }

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

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

  if (((long) w      &gt;&gt; 24) ||	/* sanity check for buffer allocation below */
      ((long) maxval &gt;&gt; 16))	/* support max 16-bit (2-byte) sample values */
    ERREXIT(cinfo, JERR_PPM_OUTOFRANGE);

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

  /* initialize flags to most common settings */
  need_iobuffer = TRUE;		/* do we need an I/O buffer? */
  use_raw_buffer = FALSE;	/* do we map input buffer onto I/O buffer? */
  need_rescale = TRUE;		/* do we need a rescale array? */

  switch (c) {
  case &#039;2&#039;:			/* it&#039;s a text-format PGM file */
    cinfo-&gt;input_components = 1;
    cinfo-&gt;in_color_space = JCS_GRAYSCALE;
    TRACEMS2(cinfo, 1, JTRC_PGM_TEXT, w, h);
    source-&gt;pub.get_pixel_rows = get_text_gray_row;
    need_iobuffer = FALSE;
    break;

  case &#039;3&#039;:			/* it&#039;s a text-format PPM file */
    cinfo-&gt;input_components = 3;
    cinfo-&gt;in_color_space = JCS_RGB;
    TRACEMS2(cinfo, 1, JTRC_PPM_TEXT, w, h);
    source-&gt;pub.get_pixel_rows = get_text_rgb_row;
    need_iobuffer = FALSE;
    break;

  case &#039;5&#039;:			/* it&#039;s a raw-format PGM file */
    cinfo-&gt;input_components = 1;
    cinfo-&gt;in_color_space = JCS_GRAYSCALE;
    TRACEMS2(cinfo, 1, JTRC_PGM, w, h);
    if (maxval &gt; 255) {
      source-&gt;pub.get_pixel_rows = get_word_gray_row;
    } else if (maxval == MAXJSAMPLE &amp;&amp; SIZEOF(JSAMPLE) == SIZEOF(U_CHAR)) {
      source-&gt;pub.get_pixel_rows = get_raw_row;
      use_raw_buffer = TRUE;
      need_rescale = FALSE;
    } else {
      source-&gt;pub.get_pixel_rows = get_scaled_gray_row;
    }
    break;

  case &#039;6&#039;:			/* it&#039;s a raw-format PPM file */
    cinfo-&gt;input_components = 3;
    cinfo-&gt;in_color_space = JCS_RGB;
    TRACEMS2(cinfo, 1, JTRC_PPM, w, h);
    if (maxval &gt; 255) {
      source-&gt;pub.get_pixel_rows = get_word_rgb_row;
    } else if (maxval == MAXJSAMPLE &amp;&amp; SIZEOF(JSAMPLE) == SIZEOF(U_CHAR)) {
      source-&gt;pub.get_pixel_rows = get_raw_row;
      use_raw_buffer = TRUE;
      need_rescale = FALSE;
    } else {
      source-&gt;pub.get_pixel_rows = get_scaled_rgb_row;
    }
    break;
  }

  /* Allocate space for I/O buffer: 1 or 3 bytes or words/pixel. */
  if (need_iobuffer) {
    source-&gt;buffer_width = (size_t) w * (size_t) cinfo-&gt;input_components *
      ((maxval &lt;= 255) ? SIZEOF(U_CHAR) : (2 * SIZEOF(U_CHAR)));
    source-&gt;iobuffer = (U_CHAR *) (*cinfo-&gt;mem-&gt;alloc_small)
      ((j_common_ptr) cinfo, JPOOL_IMAGE, source-&gt;buffer_width);
  }

  /* Create compressor input buffer. */
  if (use_raw_buffer) {
    /* For unscaled raw-input case, we can just map it onto the I/O buffer. */
    /* Cast here implies near-&gt;far pointer conversion on PCs */
    source-&gt;pixrow = (JSAMPROW) source-&gt;iobuffer;
  } else {
    /* Need to translate anyway, so make a separate sample buffer. */
    source-&gt;pixrow = (JSAMPROW) (*cinfo-&gt;mem-&gt;alloc_large)
      ((j_common_ptr) cinfo, JPOOL_IMAGE, (size_t) w *
       (size_t) cinfo-&gt;input_components * SIZEOF(JSAMPLE));
  }
  /* Synthesize a JSAMPARRAY pointer structure */
  source-&gt;pub.buffer = &amp; source-&gt;pixrow;
  source-&gt;pub.buffer_height = 1;

  /* Compute the rescaling array if required. */
  if (need_rescale) {
    INT32 val, half_maxval;

    /* On 16-bit-int machines we have to be careful of maxval = 65535 */
    source-&gt;rescale = (JSAMPLE *) (*cinfo-&gt;mem-&gt;alloc_small) ((j_common_ptr) cinfo,
      JPOOL_IMAGE, ((size_t) maxval + (size_t) 1) * SIZEOF(JSAMPLE));
    half_maxval = maxval / 2;
    for (val = 0; val &lt;= (INT32) maxval; val++) {
      /* The multiplication here must be done in 32 bits to avoid overflow */
      source-&gt;rescale[val] = (JSAMPLE) ((val * MAXJSAMPLE + half_maxval) / maxval);
    }
  }
}


/*
 * Finish up at the end of the file.
 */

METHODDEF(void)
finish_input_ppm (j_compress_ptr cinfo, cjpeg_source_ptr sinfo)
{
  /* no work */
}


/*
 * The module selection routine for PPM format input.
 */

GLOBAL(cjpeg_source_ptr)
jinit_read_ppm (j_compress_ptr cinfo)
{
  ppm_source_ptr source;

  /* Create module interface object */
  source = (ppm_source_ptr) (*cinfo-&gt;mem-&gt;alloc_small)
    ((j_common_ptr) cinfo, JPOOL_IMAGE, SIZEOF(ppm_source_struct));
  /* Fill in method ptrs, except get_pixel_rows which start_input sets */
  source-&gt;pub.start_input = start_input_ppm;
  source-&gt;pub.finish_input = finish_input_ppm;

  return &amp;source-&gt;pub;
}

#endif /* PPM_SUPPORTED */
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