Hi,
That is not true. In order for ConvertHtml render images correctly, usually you
must set HtmlToPdf.Options.BaseUrl correctly. This is needed to expand the partial Urls into full Url. For example, if you pass the following HTML to ConvertHtml:
Then unless you correctly set HtmlToPdf.Options.BaseUrl, the converter would have no idea where to download logo.gif. If you set BaseUrl, for example, "http://www.yoursite.com/app1", then it will combine that with the partial Url to form the full Url (in this case would be "http://www.yoursite.com/app1/logo.gif"). This step is crucial not only for images, but for all dependency resources (such as CSS files, JavaScript files etc).
ASPXToPDF.RenderAsPDF internally use ConvertHtml but it automatically sets HtmlToPdf.Options.BaseUrl based on the Url of the page you are trying to convert. So it all comes down to BaseUrl.
The issue should not have anything to do with base64 encoded data Url though. If you use base64 encoded data Url, it should always work regardless BaseUrl settings.
Thanks!