convertImageToDataURL

<script type="text/javascript">
// not support cross origin image 
function convertImageToDataURL(src, w, h, callback) {
    var canvas = document.createElement('canvas'),
        ctx    = canvas.getContext('2d'),
        img    = new Image();

    img.onload = function () {
        ctx.drawImage(this, 0, 0, w, h);
        callback(canvas.toDataURL());
    };

    img.src = src;
}

convertImageToDataURL('hgy.jpg', 100, 100, function (dataURL) {
    document.write('<img src="' + dataURL + '" />');
});

</script>