let mask;

let size = 50;

​

function preload() {

  bgImage = loadImage("Gradient_Test.jpg");

}

​

function setup() {

  createCanvas(displayWidth, displayHeight);

  background(0);

  bgImage.resize(displayWidth, displayHeight);

  background(0, 100);

​

  mask = createGraphics(size, size);

  mask.fill(255);

  mask.noStroke();

  mask.ellipse(size/2, size/2, size);

}

​

function draw() {

  if (mouseIsPressed) {

  let newImage = createImage(size, size);

  newImage.copy(bgImage, mouseX - size/2, mouseY - size/2, size, size, 0, 0, size, size);

​

  newImage.mask(mask);

  image(newImage, mouseX - size/2, mouseY - size/2);

  }

}