ppm.cpp

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/*
 * PPM Image Format Reader
 * Code adapted from http://stackoverflow.com/questions/2693631/read-ppm-file-and-store-it-in-an-array-coded-with-c
 * User: rpf
 * 8/1/2012
 */

#include <ompl_visual_tools/utilities/ppm.h>

namespace ompl_visual_tools
{

// *************************************************************************************************
// Reading Function
// *************************************************************************************************
PPMImage *readPPM(const char *filename)
{
  char buff[16];
  PPMImage *img;
  FILE *fp;
  int c, rgb_comp_color;

  //open PPM file for reading
  fp = fopen(filename, "rb");
  if (!fp) {
    fprintf(stderr, "Unable to open file '%s'\n", filename);
    exit(1);
  }

  //read image format
  if (!fgets(buff, sizeof(buff), fp)) {
    perror(filename);
    exit(1);
  }

  //check the image format
  if (buff[0] != 'P' || buff[1] != '6') {
    fprintf(stderr, "Invalid image format (must be 'P6')\n");
    exit(1);
  }

  //alloc memory form image
  img = (PPMImage *)malloc(sizeof(PPMImage));
  if (!img) {
    fprintf(stderr, "Unable to allocate memory\n");
    exit(1);
  }

  //check for comments
  c = getc(fp);
  while (c == '#') {
    while (getc(fp) != '\n') ;
    c = getc(fp);
  }

  ungetc(c, fp);
  //read image size information
  if (fscanf(fp, "%d %d", &img->x, &img->y) != 2) {
    fprintf(stderr, "Invalid image size (error loading '%s')\n", filename);
    exit(1);
  }

  //read rgb component
  if (fscanf(fp, "%d", &rgb_comp_color) != 1) {
    fprintf(stderr, "Invalid rgb component (error loading '%s')\n", filename);
    exit(1);
  }

  //check rgb component depth
  if (rgb_comp_color!= RGB_COMPONENT_COLOR) {
    fprintf(stderr, "'%s' does not have 8-bits components\n", filename);
    exit(1);
  }

  while (fgetc(fp) != '\n') ;
  //memory allocation for pixel data
  img->data = (PPMPixel*)malloc(img->x * img->y * sizeof(PPMPixel));

  if (!img) {
    fprintf(stderr, "Unable to allocate memory\n");
    exit(1);
  }

  //read pixel data from file
  if ( fread( img->data, 3 * img->x, img->y, fp) != img->y) {
    fprintf(stderr, "Error loading image '%s'\n", filename);
    exit(1);
  }

  // Close the file pointer
  fclose(fp);
  
  return img;
}

} // namespace