// Threshold
PImage img;

void setup() {
  img = loadImage("kodim01.png");
  //img = loadImage("colony.jpg");
  size(img.width, img.height);
  image(img, 0, 0);
}

void draw() {}

void drawImg(float thresh) {
  image(img, 0, 0);
  filter(THRESHOLD, thresh);
}

void mouseDragged() {
  float thresh = map(mouseY, 0, height, 0.0, 1.0);
  println(thresh);
  drawImg(thresh);
}