let a = 0;

let aspeed = 3;

function setup() {

  createCanvas(640, 480);

  cam = createCapture(VIDEO);

  cam.hide();

}

​

function draw() {

  background(220);

  image(cam, 0, 0);

  // drawing oustide of the canvas, negetive space, need to be negtive value to show

  push();

  // scale(x mutiplication, y mutiplication)

  scale(-1, 1);

  // in mirror, the width become negtive, filped

  // copy(img,sx,sy,sw,sh,dx,dy,dw,dh)

  copy(cam, 0, 0, width / 2, height, -width, 0, width / 2, height);

  pop();

​

  // transparency

  tint(255, a);

  image(cam, 0, 0);

​

  a += aspeed;

  if (a < 0 || a > 255) {

    aspeed *= -1;

  }

}