How can I extract the Fonts used in a PDF file via PDFSharp?

Question

I am trying to extract the fonts used in a PDF document via PDFSharp (http://www.pdfsharp.net/).

Unfortunately I am not able to do so since I keep on getting strange results and I don't know how to interpret them. In the assembly I have seen classes like PdfFontTable etc, but they are all internal. When decompiling the PdfResources class again everything related to Fonts is internal.

I have tried to access the Resources to get the fonts as:

var reader = Reader.Open(stream, PdfDocumentOpenMode.InformationOnly);
foreach (var page in reader.Pages)
{
    var resources = page.Resources;
    var fonts = resources.Elements.GetValue("/Font");
}

But that gives me an incomprehensible response:

Is there a way to extract the list of fonts used just like I see them in Adobe Acrobat Reader?

Answer 1

Eventually I managed to get it to work by registering an IEventListener and handling the TextRenderInfo.

public class FontReader : IEventListener 
{
    private ICollection<FontData> _fonts;

    /// <summary>
    ///     Gets all fonts used in a PdfDocument.
    /// </summary>
    public ICollection<FontData> GetFonts(PdfDocument document)
    {
        _fonts = new List<FontData>();
        var processor = new PdfCanvasProcessor(this);
        for (var i = 1; i <= document.GetNumberOfPages(); i++)
        {
            var page = document.GetPage(i);
            processor.ProcessPageContent(page);
        }

        return _fonts;
    }

    public void EventOccurred(IEventData data, EventType type)
    {
       if (!(data is TextRenderInfo)) return;

       var font = ((TextRenderInfo)data).GetFont();
       var name = font.GetFontProgram().GetFontNames().GetFontName();
       var type = font.GetPdfObject().GetAsName(PdfName.Subtype).GetValue();
       ...
       _fonts.Add(...);
    }
}