How do I convert a Blob URL to File (image file)

I use a React component that converts an image to a blob URL. The URL looks like this: "blob:http://localhost:3000/78db8897-645d-4323-8865-8deaa9716a96". Appending it to a works, it shows the image. But I want to be able to upload this string to the server as the file. I have a function I found here on SO but it doesn't work.

export function blobToFile(blobUrl, fileName) {
  const blob = new Blob([blobUrl], {
    lastModifiedDate: Date.now(),
    type: "image/png",
  });

  const file = new File([blob], fileName + ".png", {
    type: "image/png",
    lastModified: Date.now(),
  });
  return file;
}