Конвертация в base64 картинки по урл через canvas
convertToDataURLviaCanvas('http://bit.ly/18g0VNp', function(base64Img){
// Base64DataURL
// Ваш код
});
function convertToDataURLviaCanvas(url, callback, outputFormat){
var img = new Image();
img.crossOrigin = 'Anonymous';
img.onload = function(){
var canvas = document.createElement('CANVAS');
var ctx = canvas.getContext('2d');
var dataURL;
canvas.height = this.height;
canvas.width = this.width;
ctx.drawImage(this, 0, 0);
dataURL = canvas.toDataURL(outputFormat);
callback(dataURL);
canvas = null;
};
img.src = url;
}