Download blank image from internet by makeImageData

Hi, I use a Picture to display a internet image, when I download, the image got blank, please help how to resolve this?
Snip20210908_10
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The code is bellow:

downloadImage() {
      this.diagram.makeImageData({
        background: this.colorGroup[this.colormodel],
        returnType: "blob",
        callback: this.myCallback,
      });
    },
    myCallback(blob) {
      var url = window.URL.createObjectURL(blob);
      var filename = "myMindmap.png";

      var a = document.createElement("a");
      a.style = "display: none";
      a.href = url;
      a.download = filename;

      // IE 11
      if (window.navigator.msSaveBlob !== undefined) {
        window.navigator.msSaveBlob(blob, filename);
        return;
      }

      document.body.appendChild(a);
      requestAnimationFrame(function () {
        a.click();
        window.URL.revokeObjectURL(url);
        document.body.removeChild(a);
      });
    },

This is almost certainly a CORS security problem. You’ll need to either change the image source to allow use that way, or implement a Picture.sourceCrossOrigin function. Please read https://enable-cors.org/