SOURCE

const imgSrc = "https://i.loli.net/2018/10/19/5bc9db906f615.jpg";
let img;

function preload() {
	img = loadImage(imgSrc)
}

function setup() {
    createCanvas(img.width, img.height);
    background(0);
}

function draw() {
  for(let i= 0; i< 20; i++){
    let x = random(width);
    let y = random(height);
    let col = img.get(x, y);// 获取x，y上的像素值[r,g,b,a]
    let r = red(col);
    let g = green(col);
    let b = blue(col);
    noStroke();
    fill(r,g,b/2);
    ellipse(x,y,6);
  }
}