HTMLtoQuestPDF "cannot decode the provided image"

[marcscheuner-bfh]

My HTML template also includes an "embedded" SVG image, provided by a base64 encoded string.

<img src="data:image/svg+xml;base64,....(long list of bytes in hex form)......"
            alt="BFH Logo"
            height="160"
            class="bfh-logo">

When trying to render this with Html-to-QuestPDF, I get this exception:

QuestPDF.Drawing.Exceptions.DocumentComposeException
Message=Cannot decode the provided image.

Any idea why this doesn't work? Another image provided the very same way works fine ....