imgToDataUrl promisefied

// http://stackoverflow.com/questions/6150289/how-to-convert-image-into-base64-string-using-javascript
        function imgToDataUrl(url) {
            var deferred = $q.defer();
            var xhr = new XMLHttpRequest();
            xhr.responseType = 'blob';
            xhr.onload = function() {
                var reader = new FileReader();
                reader.onloadend = function() {
                    deferred.resolve(reader.result);
                }
                reader.readAsDataURL(xhr.response);
            };
            xhr.open('GET', url);
            xhr.send();
            return deferred.promise;
        }