function getBase64Image(img) {
                var canvas = document.createElement("canvas");
                canvas.width = img.width;
                canvas.height = img.height;
                var ctx = canvas.getContext("2d");
                ctx.drawImage(img, 0, 0, img.width, img.height);
                var ext = img.src.substring(img.src.lastIndexOf(".") + 1).toLowerCase();
                var dataURL = canvas.toDataURL("image/" + ext);
                return dataURL;
            }
            //图片转base64
            var img = $(".bill img").prop("src");
            var image = new Image();
            image.crossOrigin = '';
            image.src = img;
            var small_base64 = getBase64Image(image);