convert rgb picture to monochrome with

picture2monochrome.pde

PImage img;

void setup() {
  size(150, 200);
  noLoop();
  img = loadImage("kaefer.png");
}

void draw() {
  image(img, 0, 0);
  calcThreshold();
  for (int x = 0; x < width; x = x + 1) {
    for (int y = 0; y < height; y = y + 1) {
      color col = get(x, y);
      set(x, y, monochrome(col));
    }
  }
}

color threshold;
void calcThreshold(){
  int r, g, b;
  r = g = b = 0;
  int iPixels = width * height;
  for (int x = 0; x < width; x = x + 1) {
    for (int y = 0; y < height; y = y + 1) {
      color col = get(x, y);
      r += red(col);
      g += green(col);
      b += blue(col);
    }
  }
  threshold = color(r/iPixels, g/iPixels, b/iPixels);
}


color monochrome(color col){
  return col < threshold ? color(0) : color(255);
}