source: sans/utils/Teabag/sa_img.c @ 838

#include <stdio.h>
#include <math.h>
#include "lut.h"

int
writeppm(char * outfile, unsigned char **input, 
     int height, int width, int grey, int size) {
  FILE *fp;
  unsigned char r, g, b;
  int x, y, z, s, t;

  if ((fp = fopen(outfile,"w")) == NULL) return -1;

  /* Write header */
  fprintf(fp,"P6\n");
  fprintf(fp,"%d %d\n",width*size,height*size);
  fprintf(fp,"%d\n",255);

  /* Write pixels */
  for(y=0;y<height;y++){
    for (s=0;s<size;s++){
      for(x=0;x<width;x++){
        z = (int) input[y][x];
        if (grey) {
          r = input[y][x]; g = r; b = r;
        } else {
          r = red[z]; g = green[z]; b = blue[z];
        }
        for (t=0;t<size;t++){
          fwrite(&r,1,1,fp);
          fwrite(&g,1,1,fp);
          fwrite(&b,1,1,fp);
        }
      }
    }
  }

  fclose(fp);
  return 0;
}

int
buildcmap(int **input, int y, int x) {
  int i, j;
  //int val; 
  for(j=0;j<y;j++) {
    for(i=0;i<x;i++) input[j][i] = 0;
  }

  for(j=0;j<y;j++) {
    for(i=0;i<x;i++) input[j][i] = (y - j);
  }
  return 0;
}

/* Perform gamma correction on bitmap */
int 
reverse_img(unsigned char **input, int y, int x, int maxval) {
  int i, j;
  //int val;
  
  for(j=0;j<y;j++) {
    for(i=0;i<x;i++) {
      input[i][j] = (unsigned char) maxval - input[i][j];
    }
  }
  return 0;
}

/* Perform gamma correction on bitmap */
int 
gamma_cor(unsigned char **input, int y, int x, int maxval, float gamma) {
  int i, j;
  float val;
  
  for(j=0;j<y;j++) {
    for(i=0;i<x;i++) {
      val = ((float) input[i][j])/ ((float) maxval);
      val = pow(val,( 1 / gamma));
      val *= (float) maxval;
      input[i][j] = (unsigned char) ((int) val);
    }
  }
  return 0;
}