var w = 640;

var h = 480;

​

function setup() {

    capture = createCapture(VIDEO);

    createCanvas(w, h);

    capture.size(w, h);

    capture.hide();

}

​

function draw() {

  image(capture, 0, 0, w, h);

  capture.loadPixels();

  if (capture.pixels.length > 0) { // don't forget this! 

    var pixels = capture.pixels;

    for (var y = 0; y < height; y++) {

      for (var x = 0; x < width; x++) {

        var index = (x + y * capture.width) * 4;

        var R = pixels[index + 0];

        var G = pixels[index + 1];

        var B = pixels[index + 2];

        var A = pixels[index + 3];

​

        pixels[index + 0] = 255 - R;

        pixels[index + 1] = 255 - G;

        pixels[index + 2] = 255 - B;

      }

    }

  }

  capture.updatePixels();

}