motiondetection.js

/*
* Motion detection with nodeJS
*
* You'll need node-canvas: https://github.com/Automattic/node-canvas
*/

var Canvas = require('canvas'), 
    Image = Canvas.Image,
    canvas = new Canvas(640, 480),
    diffCanvas = new Canvas(640, 480),
    context = canvas.getContext('2d'),
    diffContext = diffCanvas.getContext('2d'),
    fs = require('fs');
    
const canvasWidth = 640;
const canvasHeight = 480;
const pixelDiffThreshold = 50;
const diffWidth = 64;
const diffHeight = 48;
const scoreThreshold = 16;
const movementPadding = 10;
const motionThreshold = 10;
    
var currentImage = fs.readFileSync('last.jpg');
var lastImage = fs.readFileSync('prelast.jpg');

var img = new Image;
img.src = currentImage;
diffContext.drawImage(img, 0, 0, canvasWidth, canvasHeight);

img = new Image;
img.src = currentImage;
context.drawImage(img, 0, 0, canvasWidth, canvasHeight);

diffContext.globalCompositeOperation = 'difference';

img = new Image;
img.src = lastImage;
diffContext.drawImage(img, 0, 0, canvasWidth, canvasHeight);

diffContext.globalCompositeOperation = 'source-on';

// predefined no-motion-areas: in my case my TV and some reflections
diffContext.fillStyle = "black";
diffContext.fillRect(canvasWidth * 0.68, canvasHeight * 0.52, canvasWidth * 0.29, canvasHeight * 0.32); // TV
diffContext.fillRect(canvasWidth * 0.05, canvasHeight * 0.25, canvasWidth * 0.05, canvasHeight * 0.15); // TV reflection
diffContext.fillRect(canvasWidth * 0.15, canvasHeight * 0.65, canvasWidth * 0.05, canvasHeight * 0.11); // TV reflection

var diff = processDiff();

if (diff.motionBox) {
    context.strokeStyle = 'green';
    context.lineWidth = 2;
    context.strokeRect(
        diff.motionBox.x[0] - movementPadding,
        diff.motionBox.y[0] - movementPadding,
        diff.motionBox.x[1] - diff.motionBox.x[0] + (movementPadding * 2),
        diff.motionBox.y[1] - diff.motionBox.y[0] + (movementPadding * 2)
    );
}


fs.writeFileSync('difference.png', diffCanvas.toBuffer());
fs.writeFileSync('movement.png', canvas.toBuffer());

console.log('processDiff', diff);

function processDiff() {
    var imageData = diffContext.getImageData(0, 0, canvasWidth, canvasHeight);
    var rgba = imageData.data;

    // pixel adjustments are done by reference directly on diffImageData
    var changedPixels = 0;
    var motionPixels = [];
    var motionBox = { x: [canvasWidth, 0], y: [canvasHeight, 0] };
    
    for (var i = 0; i < rgba.length; i += 4) {
        var brightness = 0.34 * rgba[i] + 0.5 * rgba[i + 1] + 0.16 * rgba[i + 2];
        
        coords = {
            x: (i / 4) % canvasWidth,
            y: Math.floor((i / 4) / canvasWidth)
        };
        
        if (brightness >= pixelDiffThreshold) {
            changedPixels++;
            rgba[i] = brightness;
            rgba[i + 1] = brightness;
            rgba[i + 2] = brightness;
            
            if (coords.x < motionBox.x[0]) motionBox.x[0] = coords.x;
            if (coords.y < motionBox.y[0]) motionBox.y[0] = coords.y;
            if (coords.x > motionBox.x[1]) motionBox.x[1] = coords.x;
            if (coords.y > motionBox.y[1]) motionBox.y[1] = coords.y;
        } else {
            rgba[i] = 0;
            rgba[i + 1] = 0;
            rgba[i + 2] = 0;
        }
        
    }
    
    var motionBoxWidth = motionBox.x[1] - motionBox.x[0];
    var motionBoxHeight = motionBox.y[1] - motionBox.y[0];
    
    var score = Math.round((changedPixels / (motionBoxWidth * motionBoxHeight)) * 100000) / 1000;
    
    var hasMovement = score > motionThreshold;
    
    diffContext.putImageData(imageData, 0, 0);

    return {
        score: score,
        hasMovement: hasMovement,
        motionBox: hasMovement ? motionBox : false
    }
}