实现用C#和VB.NET调用Ghostscript的API，把Postscript文件转为PDF文件。

利用Ghostscript提供的gsapi_vb实现转postscript为PDF，进一步成功把VB.NET代码转为C#。
所用GhostScript为AFPL Ghostscript 8.53
附上GhostScript提供的VB.NET代码：

' Copyright (c) 2002 Dan Mount and Ghostgum Software Pty Ltd
'
' Permission is hereby granted, free of charge, to any person obtaining
' a copy of this software and associated documentation files (the
' "Software"), to deal in the Software without restriction, including
' without limitation the rights to use, copy, modify, merge, publish,
' distribute, sublicense, and/or sell copies of the Software, and to
' permit persons to whom the Software is furnished to do so, subject to
' the following conditions:
'
' The above copyright notice and this permission notice shall be
' included in all copies or substantial portions of the Software.
'
' THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND,
' EXPRESS OR IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF
' MERCHANTABILITY, FITNESS FOR A PARTICULAR PURPOSE AND
' NONINFRINGEMENT. IN NO EVENT SHALL THE AUTHORS OR COPYRIGHT HOLDERS
' BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER LIABILITY, WHETHER IN AN
' ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM, OUT OF OR IN
' CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN THE
' SOFTWARE.

' This is an example of how to call the Ghostscript DLL from
' Visual Basic.NET. There are two examples, one converts
' colorcir.ps to PDF, the other is like command line Ghostscript.
' The display device is not supported.
'
' This code is not compatible with VB6. There is another
' example which does work with VB6. Differences include:
' 1. VB.NET uses GCHandle to get pointer
' VB6 uses StrPtr/VarPtr
' 2. VB.NET Integer is 32bits, Long is 64bits
' VB6 Integer is 16bits, Long is 32bits
' 3. VB.NET uses IntPtr for pointers
' VB6 uses Long for pointers
' 4. VB.NET strings are always Unicode
' VB6 can create an ANSI string
' See the following URL for some VB6 / VB.NET details
' http://msdn.microsoft.com/library/default.asp?url=/library/en-us/dnvb600/html/vb6tovbdotnet.asp
Option Explicit On

Imports System.Runtime.InteropServices