I'm trying to download an image and write it to the disk in Javascript. The image will be delivered base64 encoded by the server. I'm then trying to decode the image, create a blob with that data and create a new URL object. The download itself works, but the output file will be corrupted and unusable. My code looks as follows:

jsonObject = JSON.parse(requestObject.getReturnData());
decoded = atob(jsonObject['DownloadFile']);
url = window.URL.createObjectURL(new Blob([decoded], { type: "image/png" }));

aElement = document.createElement('a');
aElement.style.display = 'none';
aElement.href = url;
aElement.download = 'download.' + jsonObject['DownloadType'];

document.body.appendChild(aElement);
aElement.click();
window.URL.revokeObjectURL(url);

I verified that jsonObject['DownloadFile'] contains the correct base64 representation of the image. However, it seems that there's an error when creating the blob, since its size is too big when looking at the debug console.