encode image with base64 algorithm from image src

getBase64Image.js

function getBase64Image(img) {
    var canvas = document.createElement("canvas");
    canvas.width = img.width;
    canvas.height = img.height;

    var ctx = canvas.getContext("2d");
    ctx.drawImage(img, 0, 0);
    var dataURL = canvas.toDataURL("image/png");

    return dataURL.replace(/^data:image\/(png|jpg);base64,/, "");
}

var dataURL;
var src = "http://example.com/some_image.png";

var image = new Image();
image.src = src;
image.onload = function() {
    dataURL = getBase64Image(image);
};