void get_color(int iter, int max_iter, int* r, int* g, int* b) {
if (iter == max_iter) {
*r = *g = *b = 0; // black inside the set
return;
}
double t = (double)iter / max_iter;
int gray = (int)((1.0 - t) * 255); // whiter the furthest it was
*r = *g = *b = gray;
}