motiondetection_opencv.js

let cv = require('opencv');
let fs = require('fs');
let Jimp = require('jimp');

const imageWidth = 640;
const imageHeight = 480;
const movementPadding = 10;
const pixelDiffThreshold = 50;

var diff = new cv.Matrix(imageWidth, imageHeight);

cv.readImage('last.jpg', function(err, image1) {
    cv.readImage('prelast.jpg', function(err, image2) {
        diff.absDiff(image1, image2);
        
        diff.rectangle([imageWidth * 0.68, imageHeight * 0.52], [imageWidth * 0.29, imageHeight * 0.32], [0, 0, 0], -1); // TV
        diff.rectangle([imageWidth * 0.05, imageHeight * 0.25], [imageWidth * 0.05, imageHeight * 0.15], [0, 0, 0], -1); // TV reflection
        diff.rectangle([imageWidth * 0.15, imageHeight * 0.65], [imageWidth * 0.05, imageHeight * 0.11], [0, 0, 0], -1); // TV reflection
        
        diff.convertGrayscale();
        
        var changedPixels = 0;
        var motionBox = { x: [imageWidth, 0], y: [imageHeight, 0] };
        
        Jimp.read(diff.toBuffer(), function (err, image) {
            image.scan(0, 0, imageWidth, imageHeight, function (x, y, idx) {
                
                var brightness = 0.34 * this.bitmap.data[ idx + 0 ] + 0.5 * this.bitmap.data[ idx + 1 ] + 0.16 * this.bitmap.data[ idx + 2 ]; // get RGB values to calculate brightness
                
                if (brightness >= pixelDiffThreshold) {
                    changedPixels++;
                    this.bitmap.data[ idx + 0 ] = brightness;
                    this.bitmap.data[ idx + 1 ] = brightness;
                    this.bitmap.data[ idx + 2 ] = brightness;
                    
                    // calculate area of movement
                    if (x < motionBox.x[0]) motionBox.x[0] = x;
                    if (y < motionBox.y[0]) motionBox.y[0] = y;
                    if (x > motionBox.x[1]) motionBox.x[1] = x;
                    if (y > motionBox.y[1]) motionBox.y[1] = y;
                } else {
                    this.bitmap.data[ idx + 0 ] = 0;
                    this.bitmap.data[ idx + 1 ] = 0;
                    this.bitmap.data[ idx + 2 ] = 0;
                }
            });
            
            image.write( 'diff.jpg', saved); // save the diff graphic
            
            image1.rectangle(
                [
                    (motionBox.x[0] - movementPadding), 
                    (motionBox.y[0] - movementPadding)
                ], [
                    (motionBox.x[1] - motionBox.x[0] + (movementPadding * 2)), 
                    (motionBox.y[1] -  motionBox.y[0] + (movementPadding * 2))
                ], 
                [0, 255, 0], 
                1
            );
                    
            image1.save('movement.jpg', saved); // use image1 to show the changed area
        });
    });
});

function saved() {
    console.log('image saved!');
}