Converting a local image to base64 using JavaScript (canvas + regexp)

imageToBase64.js

function imageToBase64(img)
{
    var canvas, ctx, dataURL, base64;
    canvas = document.createElement("canvas");
    ctx = canvas.getContext("2d");
    canvas.width = img.width;
    canvas.height = img.height;
    ctx.drawImage(img, 0, 0);
    dataURL = canvas.toDataURL("image/png");
    base64 = dataURL.replace(/^data:image\/png;base64,/, "");
    return base64;
}