// intersecting color circles
//
#include <stdio.h>
 
#include "ppm.h"
 
#define N 256	  // N-by-N pixels
#define R (N/3)	  // circle radius
#define R2 (R*R)  //  and radius squared
#define XR (R)	  // coordinates of circle centers
#define YR (R)
#define XG (R)
#define YG (2*R)
#define XB (2*R)
#define YB (N/2)
 
// sum of squares
//
int sqr( int a, int b)
{
  return a*a + b*b;
}
 
int main( void)
{
  ppm a = ppm_new( N, N);
 
  for( int x = 0; x < N; ++x)
    for( int y = 0; y < N; ++y)
    {
      int c = 0;
      if( sqr(x-XR,y-YR) <= R2) { a.r[x][y] = 255; ++c; }
      if( sqr(x-XG,y-YG) <= R2) { a.g[x][y] = 255; ++c; }
      if( sqr(x-XB,y-YB) <= R2) { a.b[x][y] = 255; ++c; }
      if( c == 0) // make it white
	a.r[x][y] = a.g[x][y] = a.b[x][y] = 255;
    }
 
  ppm_write( a);
 
  return 0;
}