// Daniel Shiffman

// http://www.learningprocessing.com

​

// Example 16-13: Simple motion detection

// https://github.com/shiffman/LearningProcessing-p5.js/blob/master/chp16_video/example_16_13_MotionPixels/sketch.js

// Variable for capture device

var video;

// Previous Frame

var prevFrame;

// How different must a pixel be to be a "motion" pixel

var threshold = 50;

​

function setup() {

  createCanvas(320, 240);

  frameRate(10) ;

  pixelDensity(1);

  video = createCapture(VIDEO);

  video.size(width, height);

  video.hide();

  // Create an empty image the same size as the video

  prevFrame = createImage(video.width, video.height);

}

​

function draw() {

  image(prevFrame, 0, 0);

​

  loadPixels();

  video.loadPixels();

  prevFrame.loadPixels();

​

  // Begin loop to walk through every pixel

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

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

​

      // Step 1, what is the location into the array

      var loc = (x + y * video.width) * 4;

      // Step 2, what is the previous color

      var r1 = prevFrame.pixels[loc   ]; 

      var g1 = prevFrame.pixels[loc + 1];

      var b1 = prevFrame.pixels[loc + 2];

​

      // Step 3, what is the current color

      var r2 = video.pixels[loc   ]; 

      var g2 = video.pixels[loc + 1];

      var b2 = video.pixels[loc + 2];

​

      // Step 4, compare colors (previous vs. current)

      var diff = dist(r1, g1, b1, r2, g2, b2);

​

      // Step 5, How different are the colors?

      // If the color at that pixel has changed, then there is motion at that pixel.

      if (diff > threshold) { 

        // If motion, display black

        pixels[loc] = 0;

        pixels[loc+1] = 0;

        pixels[loc+2] = 0;

        pixels[loc+3] = 255;

      } else {

        // If not, display white

        pixels[loc] = 255;

        pixels[loc+1] = 255;

        pixels[loc+2] = 255;

        pixels[loc+3] = 255;

      }

    }

  }

  updatePixels();

​

  // Save frame for the next cycle

  //if (video.canvas) {

    prevFrame.copy(video, 0, 0, video.width, video.height, 0, 0, video.width, video.height); // Before we read the new frame, we always save the previous frame for comparison!

  //}

}