The program displays a nice arguments list that will help you to find why a file doesn't convert! Open a command prompt, enter the directory where you installed Ghostscript and execute the file gs32win.exe with the parameters as expressed in the textbox (you should only add " to enclose the path of the file that are the last 2 arguments). If you want to use this library in an ASP.NET page, you MUST copy both PDFToImage.dll and gs32dll.dll in the BIN directory of your solution! How to Debug Problems In this case, you will only have to provide input, output name and a string with the parameters as usual in the same form and order then you would provide the command line. In case your needs are different from mine, I added a way to pass the library directly the parameters you want. To use it in an ASP page, YOU MUST set the property " ThrowException" to true and now the library will only throw an exception on error and not show any Messagebox (that you could not want on an ASP page for example). Since I have seen a lot of problems regarding how to use this library, I split my project in 2 main projects, one is a DLL ( PDFToImage.dll) and the other one is the simple GUI of the DLL. Ghostscript isn't threadsafe, if you call it more than once, you MUST provide a lock system to be sure you are not calling two instances at the same time. Please verify no other instance are running!") ĬlearParameters( ref aGCHandle, ref gchandleArgs) MessageBox.Show( " I can't create a new instance of Ghostscript Be sure that we create an instance! if (intReturn < 0) IntReturn = gsapi_new_instance( out intGSInstanceHandle, _objHandle) Create a new instance of the library! try IntptrArgs = gchandleArgs.AddrOfPinnedObject() GchandleArgs = GCHandle.Alloc(aPtrArgs, GCHandleType.Pinned) GCHandle.Alloc(aAnsiArgs, GCHandleType.Pinned) ĪPtrArgs = aGCHandle.AddrOfPinnedObject() Convert the parameters for(intCounter = 0 intCounter< intElementCount intCounter++)ĪAnsiArgs = StringToAnsiZ(sArgs) Convert the Unicode strings to null terminated ANSI byte arrays // then get pointers to the byte arrays.ĪGCHandle = new GCHandle String sArgs = GetGeneratedArgs(inputFile,outputFile) These are the variables that I'm going to use int intReturn,intCounter,intElementCount (In the real code, there are also parameter checks, but I skip them here for simplicity):Ĭopy Code /// Convert a single file! /// The file PDf to convert /// The image file that will be created /// True if the conversion succeeds! public bool Convert( string inputFile, string outputFile) Pay attention to the last two, it is a common mistake to invert them! Now that we have this function, we MUST call them in this order: Private static extern void gsapi_delete_instance ( IntPtr instance) Private static extern int gsapi_exit ( IntPtr instance) Private static extern int gsapi_init_with_args ( IntPtr instance, int argc, IntPtr argv) / This will make the conversion /// /// 0 if is ok Private static extern int gsapi_new_instance ( out IntPtr pinstance, / /// /// The instance passed to other GS function The functions that are needed to call the library must be invoked using P/Invoke:Ĭopy Code /// Create a new instance of Ghostscript. How to Interface with the Ghostscript Library So in case any modification attempt should fail on this project, be sure that they are working from the command line!įor a comprehensive list of all the parameters and their meanings, I suggest you read: How to use Ghostscript. The parameters that we will provide the library are the same and in the same order that we should provide from the command line. I must convert a Unicode string to a null terminated ANSI string for Ghostscript. To perform a conversion, I needed to pass several commands to the Ghostscript interpreter. Since I know that Ghostscript performs this kind of work pretty well, I looked for a way to automate a simple conversion. I found many programs and controls that allow me to do it but they are all expensive or incomplete for my needs. Often, I found the need to perform a conversion from a PDF to an image format.īe it TIF, JPG or whatever format (I strongly suggest to convert PDF to PNG and NOT to JPEG since PNG is MUCH smaller and much better (since it has no information losses).
The program REQUIRES the DLL of Ghostscript, it can be retrieved from the Ghostscript website. After you have installed the program, just copy the gs32dll.dll from the installation directory (the bin subdirectory) to the directory where you have the EXE of my program. You will need at least GhostScript 8.64 (other versions have a problem with Vista).
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