How to convert PDF pages to PNG using Ghostscript Wrapper VB.NET? - asp.net

Question

I'm trying convert from digitally signed PDF to PNG using this solution: Simple VB.Net Wrapper for Ghostscript Dll. It doesn't work for me too. I'm using Ghostscript 9.18 32bits.
First, the source code goes to InOutErrCallBack method in this part:
gsapi_init_with_args(InstanceHndl, NumArgs + 1, Args)
When this occurr, the execution freeze. After this occurs, the next calls to RunGS method returns false in this part:
If gsapi_new_instance(InstanceHndl, IntPtr.Zero) <> 0 Then
Return False
Exit Function
End If
The return value of gsapi_new_instance is -100:
Ghostscript API - Return codes
The gswin32.dll is in C:\Windows\System32 and BIN project folder.
My parameter sequence:
Dim outputImgPath As String
outputImgPath = "C:\Download\DocumentosV2\Protocolo\Pronunciamento\" + Guid.NewGuid.ToString("N") + ".png"
Dim args() As String = { _
"-dNOPAUSE", _
"-dBATCH", _
"-dSAFER", _
"-dQUIET", _
"-sDEVICE=png16m", _
String.Format("-r{0}", resolucao), _
"-dTextAlphaBits=2", _
"-dGraphicsAlphaBits=2", _
String.Format("-dFirstPage={0}", pageNumber), _
String.Format("-dLastPage={0}", pageNumber), _
String.Format("-sOutputFile={0}", outputImgPath), _
"-f", _
pdfPath _
}
UPDATE
#kens advise me for some arguments. So, I remove it to test.
My Complete code:
Imports PdfSharp
Imports System
Imports System.Collections
Imports System.IO
Imports System.Text
Imports System.Runtime.InteropServices
Imports System.Drawing
Imports PdfSharp.Pdf
Imports PdfSharp.Pdf.IO
Imports PdfSharp.Drawing
'''
''' http://www.geekscrapbook.com/2009/11/16/c-method-to-add-an-image-to-a-pdf/
'''
Public Class PDF2Image2PDF
Inherits Simp.Net.Infra.SimpComponent
Private SyncRoot As New Object
'Converte cada página do PDF em imagem
Public Function Pdf2Png(ByVal pdfPath As String, ByVal resolucao As Int32) As Image()
Dim outputImgPath As String
Dim pageCount As Integer
Dim objPdfReader As New iTextSharp.text.pdf.PdfReader(pdfPath)
pageCount = objPdfReader.NumberOfPages()
Dim objImages As New ArrayList
For pageNumber As Int32 = 1 To pageCount
outputImgPath = "C:/Download/DocumentosV2/Protocolo/Pronunciamento/" + Guid.NewGuid.ToString("N") + ".png"
Dim objFileStream As FileStream
Dim objMemoryStream As MemoryStream
'Dim args() As String = { _
' "-dNOPAUSE", _
' "-dBATCH", _
' "-dSAFER", _
' "-dQUIET", _
' "-sDEVICE=png16m", _
' String.Format("-r{0}", resolucao), _
' "-dTextAlphaBits=2", _
' "-dGraphicsAlphaBits=2", _
' String.Format("-dFirstPage={0}", pageNumber), _
' String.Format("-dLastPage={0}", pageNumber), _
' String.Format("-sOutputFile={0}", outputImgPath), _
' "-f", _
' pdfPath _
' }
Dim args() As String = { _
"-dNOPAUSE", _
"-dBATCH", _
"-sDEVICE=png16m", _
String.Format("-dFirstPage={0}", pageNumber), _
String.Format("-dLastPage={0}", pageNumber), _
String.Format("-sOutputFile={0}", outputImgPath), _
Replace(pdfPath, "\", "/") _
}
If GhostscriptDllLib.RunGS(args) Then
If File.Exists(outputImgPath) Then
objFileStream = New FileStream(outputImgPath, FileMode.Open)
Dim length As Int32 = objFileStream.Length
Dim bytes(length) As Byte
objFileStream.Read(bytes, 0, length)
objFileStream.Close()
objMemoryStream = New MemoryStream(bytes, False)
objImages.Add(Image.FromStream(objMemoryStream))
Else
Throw New InvalidOperationException("Erro ao converter páginas do PDF em imagens PNG")
End If
Else
Throw New InvalidOperationException("Erro ao converter páginas do PDF em imagens PNG")
End If
Next
Return CType(objImages.ToArray(GetType(Image)), Image())
End Function
'Converte cada imagem do vetor em uma página do PDF
Public Function Images2PDF(ByVal imagens() As Image) As PdfDocument
Dim pdf As PdfDocument
Dim gfx As XGraphics
Dim ximg As XImage
pdf = New PdfDocument
For Each img As Image In imagens
pdf.AddPage(New PdfPage)
gfx = XGraphics.FromPdfPage(pdf.Pages.Item(0))
ximg = XImage.FromGdiPlusImage(img)
gfx.DrawImage(ximg, 0, 0)
ximg.Dispose()
gfx.Dispose()
Next
Return pdf
End Function
End Class
The Caller code:
Public Sub DownloadPeticionamento(ByVal sender As System.Object, ByVal e As System.web.UI.ImageClickEventArgs)
Dim imagem As ImageButton = DirectCast(sender, ImageButton)
Dim pdfPath As String = imagem.DescriptionUrl
Dim objPdfPeticionamento As New Simp.Net.Negocio.PDF2Image2PDF
Dim objImages() As Image
Dim objPdfDoc As PdfDocument
objImages = objPdfPeticionamento.Pdf2Png(pdfPath, 600)
objPdfDoc = objPdfPeticionamento.Images2PDF(objImages)
objPdfDoc.Save(Me.Page.Response.OutputStream, True)
End Sub
I test this in command line to:
gswin32c -dNOPAUSE -dBATCH -sDEVICE=png16m -sOutputFile=C:/Download/DocumentosV2/Protocolo/Pronunciamento/fb21872746b64f8fb31b3764b5444e2e.png C:/Upload/DocumentosV2/Protocolo/Pronunciamento/3_0_404702190_2016_10081288_230_0_f1f09b4b38ac49a8a3e5576f6041eea3.pdf
Via command line, the pdf is converted. The command line output:
C:\Documents and Settings\leandro.ferreira>gswin32c -dNOPAUSE -dBATCH -sDEVICE=png16m -dFirstPage=1 -dLastPage=1 -sOutputFile=C:/Download/DocumentosV2/Protocolo/Pronunciamento/fb21872746b64f8fb31b3764b5444e2e.png C:/Upload/DocumentosV2/Protocolo/Pronunciamento/3_0_404702190_2016_10081288_230_0_f1f09b4b38ac49a8a3e5576f6041eea3.pdf
GPL Ghostscript 9.16 (2015-03-30)
Copyright (C) 2015 Artifex Software, Inc. All rights reserved.
This software comes with NO WARRANTY: see the file PUBLIC for details.
Processing pages 1 through 1.
Page 1
Can't find (or can't open) font file %rom%Resource/Font/Arial-BoldMT.
Can't find (or can't open) font file Arial-BoldMT.
Can't find (or can't open) font file %rom%Resource/Font/Arial-BoldMT.
Can't find (or can't open) font file Arial-BoldMT.
Querying operating system for font files...
Didn't find this font on the system!
Substituting font Helvetica-Bold for Arial-BoldMT.
Loading NimbusSan-Bol font from %rom%Resource/Font/NimbusSan-Bol... 4047240 2487522 8937716 7603550 3 done.
Can't find (or can't open) font file %rom%Resource/Font/ArialMT.
Can't find (or can't open) font file ArialMT.
Can't find (or can't open) font file %rom%Resource/Font/ArialMT.
Can't find (or can't open) font file ArialMT.
Didn't find this font on the system!
Substituting font Helvetica for ArialMT.
Loading NimbusSan-Reg font from %rom%Resource/Font/NimbusSan-Reg... 4080352 2580805 9014744 7662839 3 done.
C:\Documents and Settings\leandro.ferreira>

Answer 1

-100 is simply 'fatal error' ie something really bad happened. More information is generally printed to stdout or stderr, of course setting -dQUIET will suppress much of this....
Since you are getting -100 returned its almost certainly the case that your arguments to Ghostscript are incorrect in some way.
The absolute first thing you should do when debugging problems is to try and simplify the problem, so remove any switches that you don't unquestionably require.
So the first thing to do is to remove the -dQUIET, capture all the stdout/stderr output and tell us what it says.
Further to that, note the following:
You don't need '-f' because the only purpose of that switch is to terminate -c which you haven't used.
You haven't given the values of 'resolucao', 'pageNumber', or 'pdfPath' or so there's no way to know if those are valid (or sensible). The path you have specified for outputImgPath is quite long, and includes the backslash character. I would advise using the forward slash '/' instead, as backslash is used to begin an escape and can give results you may not expect.
You've also used -dSAFER, do you understand the implications of specifying this ? If not, remove it and try again.
When you have created the string 'args' print it out. At the very least this will give you something you can try from the command line, and may mean that other people have some chance of reproducing your problem.
Finally; please note that Ghostscript is distributed under the Affero General Public Licence, please be sure to read the licence and ensure that you are conforming to the terms contained therein.

Answer 2

To do this work, I modified the Simple VB.Net Wrapper for Ghostscript Dll CallBack:
Private Function InOutErrCallBack(ByVal handle As IntPtr, _
ByVal Strz As IntPtr, ByVal Bytes As Integer) As Integer
Dim objString As String
objString = Marshal.PtrToStringAnsi(Strz, Bytes)
System.Diagnostics.Debug.WriteLine(objString)
Return Bytes
End Function
This wrotes the Ghostscript output into the Output window's Visual Studio 2003. I removed the extra "needless" arguments to Ghostscript, like -dGraphicsAlphaBits. The asp.net user does not access the Path.GetTempDir, so, I need a different "temp" dir.
'Converte cada página do PDF em imagem
Public Function Pdf2Png(ByVal pdfPath As String, ByVal tempDirPath As String, ByVal resolucao As Int32) As Image()
Dim outputImgPath As String
Dim pageCount As Integer
Dim objPdfReader As New iTextSharp.text.pdf.PdfReader(pdfPath)
pageCount = objPdfReader.NumberOfPages()
Dim objImages As New ArrayList
For pageNumber As Int32 = 1 To pageCount
outputImgPath = tempDirPath + Guid.NewGuid.ToString("N") + ".png"
Dim objFileStream As FileStream
Dim objMemoryStream As MemoryStream
'Dim args() As String = { _
' "-dNOPAUSE", _
' "-dBATCH", _
' "-dSAFER", _
' "-dQUIET", _
' "-sDEVICE=png16m", _
' String.Format("-r{0}", resolucao), _
' "-dTextAlphaBits=2", _
' "-dGraphicsAlphaBits=2", _
' String.Format("-dFirstPage={0}", pageNumber), _
' String.Format("-dLastPage={0}", pageNumber), _
' String.Format("-sOutputFile={0}", outputImgPath), _
' "-f", _
' pdfPath _
' }
Dim args() As String = { _
"-dNOPAUSE", _
"-dBATCH", _
"-sDEVICE=png16m", _
String.Format("-dFirstPage={0}", pageNumber), _
String.Format("-dLastPage={0}", pageNumber), _
String.Format("-sOutputFile={0}", outputImgPath), _
Replace(pdfPath, "\", "/") _
}
If GhostscriptDllLib.RunGS(args) Then
If File.Exists(outputImgPath) Then
objFileStream = New FileStream(outputImgPath, FileMode.Open)
Dim length As Int32 = objFileStream.Length
Dim bytes(length) As Byte
objFileStream.Read(bytes, 0, length)
objFileStream.Close()
objMemoryStream = New MemoryStream(bytes, False)
objImages.Add(Image.FromStream(objMemoryStream))
File.Delete(outputImgPath)
Else
Throw New InvalidOperationException("Erro ao converter páginas do PDF em imagens PNG")
End If
Else
Throw New InvalidOperationException("Erro ao converter páginas do PDF em imagens PNG")
End If
Next
Return CType(objImages.ToArray(GetType(Image)), Image())
End Function