int r = 25;
PImage img, original, drawn;
PImage filledImage;

void setup() {
  size(720, 480);
  img = loadImage("coding_dragon.jpg");
  original = img.get();
  drawn = createImage(720, 480, RGB);
  img.filter(GRAY);
}

void draw() {
  image(img, 0, 0);
  stroke(255, 0, 0);
  noFill();
  circle(mouseX, mouseY, r*2);


  img.loadPixels();
  original.loadPixels();
  drawn.loadPixels();
  for (int x = 0; x < width; x++) {
    for (int y = 0; y < height; y++ ) {
      float d = dist(mouseX, mouseY, x, y);
      int randomX = constrain(x + (int)random(-2, 2), 0, width-1 );
      int randomY = constrain(y + (int)random(-2, 2), 0, height-1 );
      if (d <= r) {
        if (mousePressed && mouseButton == LEFT) {
          img.pixels[y * width + x] = original.pixels[randomY * width + randomX];
          drawn.pixels[y * width + x] = color(255);
        }
      }
      //img.set(randomX, randomY, drawn.get(x, y));
    }
    img.updatePixels();
    drawn.updatePixels();
  }
}

void mousePressed() {
  if (mouseButton == RIGHT) {
    filledImage = img.get();
    img = drawn.get();
  }
}

void mouseReleased() {
  if (mouseButton == RIGHT) {
    img = filledImage;
  }
}

void keyPressed() {
  if (keyCode == UP) {
    r += 10;
  } else if (keyCode == DOWN) {
    r -= 10;
  }
  if (key == ENTER) {
    setup();
  }
}