Problem loading images into PDF using HtmlRenderer.PdfSharp

Question

This is a bit of a longshot, but maybe someone might have some ideas.

For reference - see Images don't display in PDF, a similar question.

I'm using the Htmlrenderer.PdfSharp library to create PDF files from HTML content. Everything works perfectly, with the sole exception of the images. They simply display a big red box.

The PDF works fine when running locally in debug mode, but not when deployed on the server. I've a small bit of extra information that might help - when executing the command to create the PDF:

        using (MemoryStream ms = new MemoryStream())
        {
            var pdf = TheArtOfDev.HtmlRenderer.PdfSharp.PdfGenerator.GeneratePdf(htmlContent, PdfSharp.PageSize.A4);
            pdf.Save(ms);
            res = ms.ToArray();
        }

On the server, I get a few of the following errors:

Exception thrown: 'System.Security.Authentication.AuthenticationException' in System.dll

Running locally I don't get those errors. I have a feeling it has something to do with the .NET engine not being able to properly resolve the image URL. That being said, the image URL is fully-qualified. It is, however, behind HTTPS, if that helps.

I'm unable to go any further with my debugging. If anyone has any ideas, I'd love to hear them - even if it is just more places I can try hunting for clues.

Answer 1

After quite a bit of experimenting, I've found a solution. Here's a reference to the build that allows this solution to work, so be sure you have the right version:

https://github.com/ArthurHub/HTML-Renderer/pull/41

The solution is to load the image in question into a byte array, and then load the image directly into the HTML by using a base64 string representation of the image:

byte[] array = File.ReadAllBytes(Path.Combine(AppDomain.CurrentDomain.BaseDirectory, @"[YourImageFilePathHere]"));

This will take the file from a folder within your project's deployed path - in my case, I have a folder called images, within which my image in question is located.

Next, within the CSS (or, optionally, inline if you'd like):

htmlContent += " img.logo { width:110px;height:110px;content: url('data:image/jpeg;base64," + Convert.ToBase64String(array) +"')} ";

Lastly, within the HTML:

string imageUrl = "<img class=\"logo\"></img>";

And that's it! Worked perfectly for me.