PDFSharp Export JPG - ASP.NET - vb.net

Question

I am using an ajaxfileupload control to upload a pdf file to the server. On the server side, I'd like to convert the pdf to jpg. Using the PDFsharp Sample: Export Images as a guide, I've got the following:
Imports System
Imports System.Drawing
Imports System.Drawing.Imaging
Imports PdfSharp.Pdf
Imports System.IO
Imports PdfSharp.Pdf.IO
Imports PdfSharp.Pdf.Advanced
Namespace Tools
Public Module ConvertImage
Public Sub pdf2JPG(pdfFile As String, jpgFile As String)
pdfFile = System.Web.HttpContext.Current.Request.PhysicalApplicationPath & "upload\" & pdfFile
Dim document As PdfSharp.Pdf.PdfDocument = PdfReader.Open(pdfFile)
Dim imageCount As Integer = 0
' Iterate pages
For Each page As PdfPage In document.Pages
' Get resources dictionary
Dim resources As PdfDictionary = page.Elements.GetDictionary("/Resources")
If resources IsNot Nothing Then
' Get external objects dictionary
Dim xObjects As PdfDictionary = resources.Elements.GetDictionary("/XObject")
If xObjects IsNot Nothing Then
Dim items As ICollection(Of PdfItem) = xObjects.Elements.Values
' Iterate references to external objects
For Each item As PdfItem In items
Dim reference As PdfReference = TryCast(item, PdfReference)
If reference IsNot Nothing Then
Dim xObject As PdfDictionary = TryCast(reference.Value, PdfDictionary)
' Is external object an image?
If xObject IsNot Nothing AndAlso xObject.Elements.GetString("/Subtype") = "/Image" Then
ExportImage(xObject, imageCount)
End If
End If
Next
End If
End If
Next
End Sub
Private Sub ExportImage(image As PdfDictionary, ByRef count As Integer)
Dim filter As String = image.Elements.GetName("/Filter")
Select Case filter
Case "/DCTDecode"
ExportJpegImage(image, count)
Exit Select
Case "/FlateDecode"
ExportAsPngImage(image, count)
Exit Select
End Select
End Sub
Private Sub ExportJpegImage(image As PdfDictionary, ByRef count As Integer)
' Fortunately JPEG has native support in PDF and exporting an image is just writing the stream to a file.
Dim stream As Byte() = image.Stream.Value
Dim fs As New FileStream([String].Format("Image{0}.jpeg", System.Math.Max(System.Threading.Interlocked.Increment(count), count - 1)), FileMode.Create, FileAccess.Write)
Dim bw As New BinaryWriter(fs)
bw.Write(stream)
bw.Close()
End Sub
Private Sub ExportAsPngImage(image As PdfDictionary, ByRef count As Integer)
Dim width As Integer = image.Elements.GetInteger(PdfImage.Keys.Width)
Dim height As Integer = image.Elements.GetInteger(PdfImage.Keys.Height)
Dim bitsPerComponent As Integer = image.Elements.GetInteger(PdfImage.Keys.BitsPerComponent)
' TODO: You can put the code here that converts vom PDF internal image format to a Windows bitmap
' and use GDI+ to save it in PNG format.
' It is the work of a day or two for the most important formats. Take a look at the file
' PdfSharp.Pdf.Advanced/PdfImage.cs to see how we create the PDF image formats.
' We don't need that feature at the moment and therefore will not implement it.
' If you write the code for exporting images I would be pleased to publish it in a future release
' of PDFsharp.
End Sub
End Module
End Namespace
As I debug, it blows up on Dim filter As String = image.Elements.GetName("/Filter") in ExportImage. The message is:
Unhandled exception at line 336, column 21 in ~:46138/ScriptResource.axd?d=LGq0ri4wlMGBKd-1vxLjtxNH_pd26HaruaEG_1eWx-epwPmhNKVpO8IpfHoIHzVj2Arxn5804quRprX3HtHb0OmkZFRocFIG-7a-SJYT_EwYUd--x9AHktpraSBgoZk4VJ1RMtFNwl1mULDLid5o5U9iBcuDi4EQpbpswgBn_oI1&t=ffffffffda74082d
0x800a139e - JavaScript runtime error: error raising upload complete event and start new upload
Any thoughts on what the issue might be? It seems an issue with the ajaxfileupload control, but I don't understand why it would be barking here. It's neither here nor there, but I know I'm not using jpgFile yet.

Answer 1

PDFsharp cannot create JPEG Images from PDF pages:
http://pdfsharp.net/wiki/PDFsharpFAQ.ashx#Can_PDFsharp_show_PDF_files_Print_PDF_files_Create_images_from_PDF_files_3
The sample you refer to can extract JPEG Images that are included in PDF files. That's all. The sample does not cover all possible cases.
Long story short: the code you are showing seems unrelated to the error message. And it seems unrelated to your intended goal.