/* 
 * rdppm.c 
 * 
 * Copyright (C) 1991-1997, Thomas G. Lane. 
 * This file is part of the Independent JPEG Group'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). 
 */ 
 
#include "cdjpeg.h"		/* Common decls for cjpeg/djpeg applications */ 
 
#ifdef PPM_SUPPORTED 
 
 
/* 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 "as is" without express or 
** implied warranty. 
*/ 
 
 
/* 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 */ 
#ifdef CHAR_IS_UNSIGNED 
typedef char U_CHAR; 
#define UCH(x)	((int) (x)) 
#else 
typedef char U_CHAR; 
#define UCH(x)	((int) (x) & 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'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++); 
    temp |= UCH(*bufferptr++) << 8; 
    *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++); 
    temp |= UCH(*bufferptr++) << 8; 
    *ptr++ = rescale[temp]; 
    temp  = UCH(*bufferptr++); 
    temp |= UCH(*bufferptr++) << 8; 
    *ptr++ = rescale[temp]; 
    temp  = UCH(*bufferptr++); 
    temp |= UCH(*bufferptr++) << 8; 
    *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 */ 
  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 '2':			/* it's a text-format PGM file */ 
    cinfo->input_components = 1; 
    cinfo->in_color_space = JCS_GRAYSCALE; 
    TRACEMS2(cinfo, 1, JTRC_PGM_TEXT, w, h); 
    source->pub.get_pixel_rows = get_text_gray_row; 
    need_iobuffer = FALSE; 
    break; 
 
  case '3':			/* it's a text-format PPM file */ 
    cinfo->input_components = 3; 
    cinfo->in_color_space = JCS_RGB; 
    TRACEMS2(cinfo, 1, JTRC_PPM_TEXT, w, h); 
    source->pub.get_pixel_rows = get_text_rgb_row; 
    need_iobuffer = FALSE; 
    break; 
 
  case '5':			/* it's a raw-format PGM file */ 
    cinfo->input_components = 1; 
    cinfo->in_color_space = JCS_GRAYSCALE; 
    TRACEMS2(cinfo, 1, JTRC_PGM, w, h); 
    if (maxval > 255) { 
      source->pub.get_pixel_rows = get_word_gray_row; 
    } else if (maxval == MAXJSAMPLE && SIZEOF(JSAMPLE) == SIZEOF(U_CHAR)) { 
      source->pub.get_pixel_rows = get_raw_row; 
      use_raw_buffer = TRUE; 
      need_rescale = FALSE; 
    } else { 
      source->pub.get_pixel_rows = get_scaled_gray_row; 
    } 
    break; 
 
  case '6':			/* it's a raw-format PPM file */ 
    cinfo->input_components = 3; 
    cinfo->in_color_space = JCS_RGB; 
    TRACEMS2(cinfo, 1, JTRC_PPM, w, h); 
    if (maxval > 255) { 
      source->pub.get_pixel_rows = get_word_rgb_row; 
    } else if (maxval == MAXJSAMPLE && SIZEOF(JSAMPLE) == SIZEOF(U_CHAR)) { 
      source->pub.get_pixel_rows = get_raw_row; 
      use_raw_buffer = TRUE; 
      need_rescale = FALSE; 
    } else { 
      source->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->buffer_width = (size_t) w * cinfo->input_components * 
      ((maxval<=255) ? SIZEOF(U_CHAR) : (2*SIZEOF(U_CHAR))); 
    source->iobuffer = (U_CHAR *) 
      (*cinfo->mem->alloc_small) ((j_common_ptr) cinfo, JPOOL_IMAGE, 
				  source->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. */ 
    /* Synthesize a JSAMPARRAY pointer structure */ 
    /* Cast here implies near->far pointer conversion on PCs */ 
    source->pixrow = (JSAMPROW) source->iobuffer; 
    source->pub.buffer = & source->pixrow; 
    source->pub.buffer_height = 1; 
  } else { 
    /* Need to translate anyway, so make a separate sample buffer. */ 
    source->pub.buffer = (*cinfo->mem->alloc_sarray) 
      ((j_common_ptr) cinfo, JPOOL_IMAGE, 
       (JDIMENSION) w * cinfo->input_components, (JDIMENSION) 1); 
    source->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->rescale = (JSAMPLE *) 
      (*cinfo->mem->alloc_small) ((j_common_ptr) cinfo, JPOOL_IMAGE, 
				  (size_t) (((long) maxval + 1L) * SIZEOF(JSAMPLE))); 
    half_maxval = maxval / 2; 
    for (val = 0; val <= (INT32) maxval; val++) { 
      /* The multiplication here must be done in 32 bits to avoid overflow */ 
      source->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->mem->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->pub.start_input = start_input_ppm; 
  source->pub.finish_input = finish_input_ppm; 
 
  return (cjpeg_source_ptr) source; 
} 
 
#endif /* PPM_SUPPORTED */ 
