Nada relevante, olvidar esto

displacement.js

function draw(screen) {
  for(var i = 0; i < 640 * 480; i++) {
    var r = screen[i * 3 + 0];
    var g = screen[i * 3 + 1];
    var b = screen[i * 3 + 2];

    var idx = (r + g + b) - (r + g + b) % 3;

    imgdata.data[i * 4 + 0] = screen[i * 3 + idx + 0];
    imgdata.data[i * 4 + 1] = screen[i * 3 + idx + 1];
    imgdata.data[i * 4 + 2] = screen[i * 3 + idx + 2];
    imgdata.data[i * 4 + 3] = 255
  }
  c2d.putImageData(imgdata, 0, 0);
}