downloadIamge(imgsrc, name) {
                //下载图片地址和图片名
                var image = new Image();
                // 解决跨域 Canvas 污染问题
                image.setAttribute("crossOrigin", "anonymous");
                image.onload = function() {
                    var canvas = document.createElement("canvas");
                    canvas.width = image.width;
                    canvas.height = image.height;
                    var context = canvas.getContext("2d");
                    context.drawImage(image, 0, 0, image.width, image.height);
                    var url = canvas.toDataURL("image/png"); //得到图片的base64编码数据'
                    var a = document.createElement("a"); // 生成一个a元素
                    var event = new MouseEvent("click", {
                        bubbles: true,
                        cancelable: true,
                        view: window
                    }); // 创建一个单击事件
                    a.download = name || "photo"; // 设置图片名称
                    a.href = url; // 将生成的URL设置为a.href属性
                    a.dispatchEvent(event); // 触发a的单击事件
                };
                image.src = imgsrc;
            },

调用：

var fileName =  new Date().getTime() + ".png";
this.downloadIamge(“图片地址”, fileName);