如何使用Ghostscript包装器VB.NET将PDF页面转换为PNG？
如何使用Ghostscript包装器VB.NET将PDF页面转换为PNG？
提问于 2016-02-17 13:03:22
我正在尝试使用以下解决方案：Ghostscript Dll的简单VB.Net包装器将数字签名的PDF转换为PNG。对我也没用。我使用的是Ghostscript 9.18 32位。
首先，源代码转到本部分中的InOutErrCallBack方法：
gsapi_init_with_args(InstanceHndl, NumArgs + 1, Args)当这种情况发生时，执行就会冻结。发生这种情况后，在本部分中，对RunGS方法的下一次调用将返回false：
If gsapi_new_instance(InstanceHndl, IntPtr.Zero) <> 0 Then
Return False
Exit Function
End Ifgsapi_new_instance的返回值为-100：Ghostscript API -返回代码。
gswin32.dll位于C:\Windows\System32 32和BIN项目文件夹中。
我的参数序列：
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 _
}更新
@kens建议我进行一些争论。所以，我把它拿去测试。
我的完整代码：
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呼叫者代码：
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我在命令行中测试这一点，以便：
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通过命令行，pdf被转换。命令行输出：
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>回答 2
Stack Overflow用户
回答已采纳
发布于 2016-02-17 13:36:10
‘.’更多的信息通常被打印到stdout或stderr中，当然设置-dQUIET会抑制这其中的大部分.
由于您要返回-100，所以几乎可以肯定，您对Ghostscript的论点在某种程度上是不正确的。
在调试问题时，您应该做的第一件事就是尝试简化问题，因此删除所有您不需要的开关。
因此，首先要做的是删除-dQUIET，捕获所有stdout/stderr输出，并告诉我们它说了什么。
此外，请注意以下几点：
您不需要'-f‘，因为该开关的唯一目的是终止尚未使用的-c。
您还没有给出“resolucao”、“pageNumber”或“pdfPath”之类的值，因此无法知道这些值是否有效(或合理)。您为outputImgPath指定的路径相当长，包括反斜杠字符。我建议使用正斜杠'/‘代替，因为反斜杠用于开始转义，并且可以给出您可能不期望的结果。
您也使用过-dSAFER，您了解指定这一点的含义吗？如果没有，请移除，然后再试一次。
创建字符串'args‘时，将其打印出来。至少，这将给您提供一些您可以从命令行尝试的东西，并且可能意味着其他人有机会重现您的问题。
最后，请注意，Ghostscript是根据阿弗莱罗通用公共许可证分发的，请务必阅读许可证，并确保您符合其中所载的条款。
Stack Overflow用户
发布于 2016-02-17 20:49:06
为此，我修改了Ghostscript Dll的简单VB.Net包装器 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这会将Ghostscript输出转到 output 窗口的Visual 2003中。我将额外的“不必要”参数移除给Ghostscript，比如-dGraphicsAlphaBits。asp.net用户不访问Path.GetTempDir，因此，我需要一个不同的“临时”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页面原文内容由Stack Overflow提供。腾讯云小微IT领域专用引擎提供翻译支持
原文链接：
https://stackoverflow.com/questions/35457525
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