/* Builds a 2d checkerboard of red and green squares, with whatever number
   of pixels per square you want. */

/* Function to create an array of pixels, alternating green and red, with
   the given number of pixels per square. Returns the array. */

GLubyte* init_checkerboard(int pixels_per_square) {
    int i,j;
    int pps = pixels_per_square;
    int bytes = pps*pps*64*3;
    GLubyte* checkerboard = (GLubyte*) malloc(bytes);
    /* The following is a red&green checkerboard.  It's done using a 1D
       array alternating colors. We change colors every pps. */
    int count=0;
    for(i=0;i<pps*8;++i) 
	for(j=0;j<pps*8;++j) {
	    if((i&pps)^(j&pps)) {
		checkerboard[count++] = 255;
		checkerboard[count++] = 0;
		checkerboard[count++] = 0;
	    } else {
		checkerboard[count++] = 0;
		checkerboard[count++] = 255;
		checkerboard[count++] = 0;
	    }
	}
    if(bytes!=count) 
	printf("bytes = %d count = %d\n",bytes,count);
    return checkerboard;
}