pgm.c

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/*
Copyright (C) 2007-12 Andrea Vedaldi and Brian Fulkerson.
Copyright (C) 2013 Andrea Vedaldi.
All rights reserved.

This file is part of the VLFeat library and is made available under
the terms of the BSD license (see the COPYING file).
*/

#include "pgm.h"

#include <stdio.h>
#include <stdlib.h>
#include <string.h>

static int
remove_line(FILE* f)
{
  int count = 0 ;
  int c ;

  while (1) {
    c = fgetc(f) ;
    ++ count ;

    switch(c) {
    case '\n' :
      goto quit_remove_line ;

    case EOF :
      -- count ;
      goto quit_remove_line ;
    }
  }
 quit_remove_line :
  return count ;
}

static int
remove_blanks(FILE* f)
{
  int count = 0 ;
  int c ;

  while (1) {
    c = fgetc(f) ;

    switch(c) {

    case '\t' : case '\n' :
    case '\r' : case ' '  :
      ++ count ;
      break ;

    case '#' :
      count += 1 + remove_line(f) ;
      break ;

    case EOF :
      goto quit_remove_blanks ;

    default:
      ungetc(c, f) ;
      goto quit_remove_blanks ;
    }
  }
 quit_remove_blanks:
  return count ;
}

VL_EXPORT vl_size
vl_pgm_get_npixels (VlPgmImage const *im)
{
  return im->width * im->height ;
}

VL_EXPORT vl_size
vl_pgm_get_bpp (VlPgmImage const *im)
{
  return (im->max_value >= 256) + 1 ;
}

VL_EXPORT int
vl_pgm_extract_head (FILE* f, VlPgmImage *im)
{
  char magic [2] ;
  int c ;
  int is_raw ;
  int width ;
  int height ;
  int max_value ;
  size_t sz ;
  vl_bool good ;

  /* -----------------------------------------------------------------
   *                                                check magic number
   * -------------------------------------------------------------- */
  sz = fread(magic, 1, 2, f) ;

  if (sz < 2) {
    return vl_set_last_error(VL_ERR_PGM_INV_HEAD, "Invalid PGM header") ;
  }

  good = magic [0] == 'P' ;

  switch (magic [1]) {
  case '2' : /* ASCII format */
    is_raw = 0 ;
    break ;

  case '5' : /* RAW format */
    is_raw = 1 ;
    break ;

  default :
    good = 0 ;
    break ;
  }

  if( ! good ) {
    return vl_set_last_error(VL_ERR_PGM_INV_HEAD, "Invalid PGM header") ;
  }

  /* -----------------------------------------------------------------
   *                                    parse width, height, max_value
   * -------------------------------------------------------------- */
  good = 1 ;

  c = remove_blanks(f) ;
  good &= c > 0 ;

  c = fscanf(f, "%d", &width) ;
  good &= c == 1 ;

  c = remove_blanks(f) ;
  good &= c > 0 ;

  c = fscanf(f, "%d", &height) ;
  good &= c == 1 ;

  c = remove_blanks(f) ;
  good &= c > 0 ;

  c = fscanf(f, "%d", &max_value) ;
  good &= c == 1 ;

  /* must end with a single blank */
  c = fgetc(f) ;
  good &=
    c == '\n' ||
    c == '\t' ||
    c == ' '  ||
    c == '\r' ;

  if(! good) {
    return vl_set_last_error(VL_ERR_PGM_INV_META, "Invalid PGM meta information");
  }

  if(! max_value >= 65536) {
    return vl_set_last_error(VL_ERR_PGM_INV_META, "Invalid PGM meta information");
  }

  /* exit */
  im-> width     = width ;
  im-> height    = height ;
  im-> max_value = max_value ;
  im-> is_raw    = is_raw ;
  return 0 ;
}

VL_EXPORT
int
vl_pgm_extract_data (FILE* f, VlPgmImage const *im, void *data)
{
  vl_size bpp = vl_pgm_get_bpp(im) ;
  vl_size data_size = vl_pgm_get_npixels(im) ;
  vl_bool good = 1 ;
  size_t c ;

  /* -----------------------------------------------------------------
   *                                                         read data
   * -------------------------------------------------------------- */

  /*
     In RAW mode we read directly an array of bytes or shorts.  In
     the latter case, however, we must take care of the
     endianess. PGM files are sorted in big-endian format. If our
     architecture is little endian, we must do a conversion.
  */
  if (im->is_raw) {

    c = fread( data,
               bpp,
               data_size,
               f ) ;
    good = (c == data_size) ;

    /* adjust endianess */
#if defined(VL_ARCH_LITTLE_ENDIAN)
    if (bpp == 2) {
      vl_uindex i ;
      vl_uint8 *pt = (vl_uint8*) data ;
      for(i = 0 ; i < 2 * data_size ; i += 2) {
        vl_uint8 tmp = pt [i] ;
        pt [i]   = pt [i+1] ;
        pt [i+1] = tmp ;
      }
    }
#endif
  }
  /*
     In ASCII mode we read a sequence of decimal numbers separated
     by whitespaces.
  */
  else {
    vl_uindex i ;
    int unsigned v ;
    for(good = 1, i = 0 ;
        i < data_size && good ;
        ++i) {
      c = fscanf(f, " %ud", &v) ;
      if (bpp == 1) {
        * ((vl_uint8* )  data + i) = (vl_uint8)  v ;
      } else {
        * ((vl_uint16*)  data + i) = (vl_uint16) v ;
      }
      good &= c == 1 ;
    }
  }

  if(! good ) {
    return vl_set_last_error(VL_ERR_PGM_INV_DATA, "Invalid PGM data") ;
  }
  return 0 ;
}

VL_EXPORT
int
vl_pgm_insert(FILE* f, VlPgmImage const *im, void const *data)
{
  vl_size bpp = vl_pgm_get_bpp (im) ;
  vl_size data_size = vl_pgm_get_npixels (im) ;
  size_t c ;

  /* write preamble */
  fprintf(f,
          "P5\n%d\n%d\n%d\n",
          (signed)im->width,
          (signed)im->height,
          (signed)im->max_value) ;

  /* take care of endianness */
#if defined(VL_ARCH_LITTLE_ENDIAN)
  if (bpp == 2) {
    vl_uindex i ;
    vl_uint8* temp = vl_malloc (2 * data_size) ;
    memcpy(temp, data, 2 * data_size) ;
    for(i = 0 ; i < 2 * data_size ; i += 2) {
      vl_uint8 tmp = temp [i] ;
      temp [i]   = temp [i+1] ;
      temp [i+1] = tmp ;
    }
    c = fwrite(temp, 2, data_size, f) ;
    vl_free (temp) ;
  }
  else {
#endif
    c = fwrite(data, bpp, data_size, f) ;
#if defined(VL_ARCH_LITTLE_ENDIAN)
  }
#endif

  if(c != data_size) {
    return vl_set_last_error(VL_ERR_PGM_IO, "Error writing PGM data") ;
  }
  return 0 ;
}

VL_EXPORT
int vl_pgm_read_new (char const *name, VlPgmImage *im, vl_uint8** data)
{
  int err = 0 ;
  FILE *f = fopen (name, "rb") ;

  if (! f) {
    return vl_set_last_error(VL_ERR_PGM_IO, "Error opening PGM file `%s' for reading", name) ;
  }

  err = vl_pgm_extract_head(f, im) ;
  if (err) {
    fclose (f) ;
    return err ;
  }

  if (vl_pgm_get_bpp(im) > 1) {
    return vl_set_last_error(VL_ERR_BAD_ARG, "PGM with BPP > 1 not supported") ;
  }

  *data = vl_malloc (vl_pgm_get_npixels(im) * sizeof(vl_uint8)) ;
  err = vl_pgm_extract_data(f, im, *data) ;

  if (err) {
    vl_free (data) ;
    fclose (f) ;
  }

  fclose (f) ;
  return err ;
}

VL_EXPORT
int vl_pgm_read_new_f (char const *name,  VlPgmImage *im, float** data)
{
  int err = 0 ;
  size_t npixels ;
  vl_uint8 *idata ;

  err = vl_pgm_read_new (name, im, &idata) ;
  if (err) {
    return err ;
  }

  npixels = vl_pgm_get_npixels(im) ;
  *data = vl_malloc (sizeof(float) * npixels) ;
  {
    size_t k ;
    float scale = 1.0f / (float)im->max_value ;
    for (k = 0 ; k < npixels ; ++ k) (*data)[k] = scale * idata[k] ;
  }

  vl_free (idata) ;
  return 0 ;
}

VL_EXPORT
int vl_pgm_write (char const *name, vl_uint8 const* data, int width, int height)
{
  int err = 0 ;
  VlPgmImage pgm ;
  FILE *f = fopen (name, "wb") ;

  if (! f) {
    return vl_set_last_error(VL_ERR_PGM_IO,
             "Error opening PGM file '%s' for writing", name) ;
  }

  pgm.width = width ;
  pgm.height = height ;
  pgm.is_raw = 1 ;
  pgm.max_value = 255 ;

  err = vl_pgm_insert (f, &pgm, data) ;
  fclose (f) ;

  return err ;
}

VL_EXPORT
int vl_pgm_write_f (char const *name, float const* data, int width, int height)
{
  int err = 0 ;
  int k ;
  float min = + VL_INFINITY_F ;
  float max = - VL_INFINITY_F ;
  float scale ;

  vl_uint8 * buffer = vl_malloc (sizeof(float) * width * height) ;

  for (k = 0 ; k < width * height ; ++k) {
    min = VL_MIN(min, data [k]) ;
    max = VL_MAX(max, data [k]) ;
  }

  scale = 255 / (max - min + VL_EPSILON_F) ;

  for (k = 0 ; k < width * height ; ++k) {
    buffer [k] = (vl_uint8) ((data [k] - min) * scale) ;
  }

  err = vl_pgm_write (name, buffer, width, height) ;

  vl_free (buffer) ;
  return err ;
}