var stepSize = 10;

​

function setup() { 

  createCanvas(400, 300);

  capture = createCapture(VIDEO);

  capture.size(400, 300);

  //capture.hide();

  noStroke();

} 

​

function draw() { 

  background(0);

  capture.loadPixels();

  stepSize = floor(map(mouseX, 0, width, 5, 30));

  //image(capture, 0, 0);

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

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

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

      var redVal = capture.pixels[index];

      var greenVal = capture.pixels[index + 1];

      var blueVal = capture.pixels[index + 2];

      var b = redVal/255;

      fill(200, 0, 200);

      ellipse(x, y, stepSize, stepSize*b);

    }

  }

}

​

//400 * 300 = 120,000

//[r, g, b, a]