js 下載 base64 格式的圖片

    download() {
      this.resultDialog.picture.map((res, i) => {
        this.downloadFile(`證據 ${i + 1}.png`, res) // 此處 res 爲 base64 數據圖片 (data:image/jpg;base64,/.....)
      })
    },
    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 不加後兩個參數在FF下會報錯  事件類型，是否冒泡，是否阻止瀏覽器的默認行爲
      aLink.download = fileName;
      aLink.href = URL.createObjectURL(blob);

      // aLink.dispatchEvent(evt);
      aLink.click()
    },
    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 });
    },