Take a screenshot of modelviewer .glb file

I'm trying to take a screenshot of a .glb file displayed by model-viewer. But I can't arrive to a solution. I've read somewhere that the key is to convert the modelviewer to a blob object and then download an image.

<div class="button">
    <a id="download" href="#">Download button</a>
  </div>
  
<script>

function download() {
  const modelViewer =  document.querySelector("#modelviewertest");
  const screenshot = URL.createObjectURL(
      modelViewer.toBlob("image/jpeg")
    );
  const donwloadLink = document.querySelector("#download");
  donwloadLink.download = screenshot;
  donwloadLink.href = data;
}

I have tried to take a screenshot with html2canvas but not working. I would like to save into my server a screenshot of the glb model loaded on model-viewer.

There's a sample of taking a screenshot and downloading it here. The code is listed here in case the link goes down. Attribution goes to @milesgreen on GitHub, posted through this issue.

const modelViewer = document.getElementById("viewer");

async function downloadPosterToBlob() {
    const blob = await modelViewer.toBlob({ idealAspect: false });
    const url = URL.createObjectURL(blob);
    const a = document.createElement("a");
    a.href = url;
    a.download = "modelViewer_toBlob.png";
    a.click();
    URL.revokeObjectURL(url);
}

function downloadPosterToDataURL() {
    const url = modelViewer.toDataURL();
    const a = document.createElement("a");
    a.href = url;
    a.download = "modelViewer_toDataURL.png";
    a.click();
    URL.revokeObjectURL(url);
}

The JavaScript above references an HTML element that has an ID set to "viewer".

<model-viewer id="viewer"
              alt="Two cylinder engine"
              src="models/2CylinderEngine.glb"
              shadow-intensity="1"
              camera-controls touch-action="pan-y">
</model-viewer>

Add a button in HTML and connect to its click event to trigger the download function above:

document.querySelector("#download-button").addEventListener("click", downloadPosterToBlob);

<button id="download-button">Download</button>

Reference to the model-viewer web component's toBlob() method.