How to load image pixels in javascript

canvas-image.js

function loadImage(canvas, src, x, y, width, height, opt_callback) {
            var img = new window.Image();
            img.crossOrigin = '*';
            img.onload = function () {
                var context = canvas.getContext('2d');
                canvas.width = width;
                canvas.height = height;
                context.drawImage(img, x, y, width, height);
                opt_callback && opt_callback();
                img = null;
            };
            img.src = src;
        };


        var canvas = document.createElement('canvas');
        var width = 512;
        var height = 512;

        canvas.width = width;
        canvas.height = height;
        loadImage(
            canvas,
            'https://upload.wikimedia.org/wikipedia/en/2/24/Lenna.png',
            0, 0,
            width, height,
            () => {
                var context = canvas.getContext('2d');
                var imageData = context.getImageData(0, 0, width, height);
                console.log(imageData);
            });