// Count the number of colours used in a JPEG image.
// Faster version using quantization.
// Compile: gcc colourCount_quant.c -o colourCount_quant -lgd

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

int main(int argc, char *argv[]) {
 gdImagePtr image;
 FILE *png;
 int q=25; // quantization factor
 int c,x,y,i,cq;
 int *seen;
 int mem_size;
 int seen_size=0,found;
 if (argc<2) {
  printf("Syntax: colourCount_quant <image.jpg>\n");
  exit(1);
 }
 png = fopen(argv[1], "rb");
 if(png==NULL) {
  printf("Unable to open %s\n",argv[1]);
  exit(1);
 }
 image = gdImageCreateFromJpeg(png);
 fclose(png);
 mem_size=sizeof(int)*image->sx*image->sy;
 seen=malloc(mem_size);
 for (x=0;x<image->sx;x++) {
  for (y=0;y<image->sy;y++) {
   c=gdImageGetPixel(image,x,y);
   cq=(256/q)*(256/q)*(gdTrueColorGetRed(c)/q)+(256/q)*(gdTrueColorGetGreen(c)/q)+gdTrueColorGetBlue(c)/q;
   found=0;
   for (i=0;i<seen_size;i++) {
    if (seen[i]==cq) {found=1;break;}
   }
   if (found==0) {
    seen[seen_size]=cq;
    seen_size++;
   }
  } 
 }
 free(seen);
 printf("%s\t%d\n",argv[1],seen_size);
 gdImageDestroy(image);
 return 0;
}