function preload(){

      room = loadImage("yq.jpg")

    }

    function setup() {

      cnv = createCanvas(500, 300);

      centerCanvas();

      mask_layer = createGraphics(width, height)

      img = createImage(width,height)

    }

    function draw() {

      background("balck");

      mask_layer.rect(random(width),random(height),random(30,50),random(50,20),10)

      img.copy(room,0,0,room.width,room.height,0,0,width,height)

      img.mask(mask_layer)

      image(img, 0, 0,width,height)

    }

​

    function centerCanvas() {

      var x = (windowWidth - width) / 2;

      var y = (windowHeight - height) / 2;

      cnv.position(x, y);

    }

    function keyPressed(){

      if(key == 'c'){

        mask_layer.clear()

      }else if(key == 's'){

        saveGif("mask.gif",5)

      }

    }

    function windowResized(){

      centerCanvas()

    }

​