Found at http://stackoverflow.com/questions/934012/get-image-data-in-javascript

Base64 from image

function getBase64FromImageUrl(URL) {
    var img = new Image();
    img.src = URL;
    img.onload = function () {


    var canvas = document.createElement("canvas");
    canvas.width =this.width;
    canvas.height =this.height;

    var ctx = canvas.getContext("2d");
    ctx.drawImage(this, 0, 0);


    var dataURL = canvas.toDataURL("image/png");

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

    }
}