float cX = -0.7;
float cY = 0.27015;
float zx, zy;
float maxIter = 300;

void setup() {
  size(640, 480);
}

void draw() {
  for (int x = 0; x < width; x++) {
    for (int y = 0; y < height; y++) {
      zx = 1.5 * (x - width / 2) / (0.5 * width);
      zy = (y - height / 2) / (0.5 * height);
      float i = maxIter;
      while (zx * zx + zy * zy < 4 && i > 0) {
        float tmp = zx * zx - zy * zy + cX;
        zy = 2.0 * zx * zy + cY;
        zx = tmp;
        i -= 1;
      }
     colorMode(HSB);
     color c = color(i / maxIter * 255, 255,  i > 1 ? 255 : 0);
     set(x, y, c);
    }
  }
  noLoop();
}