let mag = 4;

let cutSize = 50;

​

function preload() {

  img = loadImage('data/sunflower.jpg');

}

​

function setup() {

  createCanvas(img.width, img.height);

}

​

function draw() {

  background(20);

  image(img, 0, 0);

  let piece = img.get(mouseX - (cutSize / 2),

    mouseY - (cutSize / 2),

    cutSize, cutSize);

​

  let magSize = cutSize * mag;

  image(piece,

    mouseX - (magSize / 2),

    mouseY - (magSize / 2),

    magSize, magSize);

}