图片（base64）下载到本地

//下载图片
      download() {
        let imgData = base64---------;//这里放需要下载的base64
        this.downloadFile(测试.png, imgData);
      },
      //下载
      downloadFile(fileName, content) {
        let aLink = document.createElement(a);
        let blob = this.base64ToBlob(content); //new Blob([content]);

        let evt = document.createEvent("HTMLEvents");
        evt.initEvent("click", true, true);//initEvent 不加后两个参数在FF下会报错  事件类型，是否冒泡，是否阻止浏览器的默认行为
        aLink.download = fileName;
        aLink.href = URL.createObjectURL(blob);

        // aLink.dispatchEvent(evt);
        aLink.click()
      },
      //base64转blob
      base64ToBlob(code) {
        let parts = code.split(;base64,);
        let contentType = parts[0].split(:)[1];
        let raw = window.atob(parts[1]);
        let rawLength = raw.length;

        let uInt8Array = new Uint8Array(rawLength);

        for (let i = 0; i < rawLength; ++i) {
          uInt8Array[i] = raw.charCodeAt(i);
        }
        return new Blob([uInt8Array], {type: contentType});
      },