var imgClone;

var mk;

// based on the original sketch by oshoham

​

​

​

function setup() {

    createCanvas(windowWidth, windowHeight);

     noStroke();

    img = createGraphics(width, height);

    img.fill(200);

    img.noStroke();

    img.ellipse(100, 100, 100 + 2, 100 + 2);

​

    mk = createGraphics(width, height);

    mk.rect(0, 0, 125, 125);

​

    ( imgClone = img.get() ).mask( mk.get() );

}

function draw() {

    background(200);

      noStroke();

      fill(255);

      ellipse(100, 100, 100, 100);

      image(imgClone, 0, 0);

​

}