EPOCALIPSE IFILTER PDF

Download source files and demo project - Its main purpose is to extract text from files so the Indexing Service can index them and later search them. Some versions of Windows comes with IFilter implementations for Office files, and there are free and commercial filters available for other file types Adobe PDF filter is a popular one. Although the IFilter interface can be used for general purpose text extraction from documents, it is generally used in search engines.

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Download source files and demo project - Its main purpose is to extract text from files so the Indexing Service can index them and later search them. Some versions of Windows comes with IFilter implementations for Office files, and there are free and commercial filters available for other file types Adobe PDF filter is a popular one. Although the IFilter interface can be used for general purpose text extraction from documents, it is generally used in search engines.

Windows Desktop Search uses filters to index files. For more information on IFilter, see the Links section. So what else is new? There are already quite a few articles and pieces of information on how to use the IFilter interface in. NET see the Links section , so why write another article you ask? Well, there are some problems with the implementations offered in those articles details below which caused me to take a different approach to using and loading filters.

COM threading issues. Extracting text from very large files All of the sample code I found on using IFilters in C provided a method that extracts the entire text of a document and returns that as a string. Some documents may be very large 30 MB PDFs or Word documents are not uncommon , and extracting the entire text at once can have negative effects on the garbage collector since these objects will be stored in the.

See the Links section for some of the reported problems. We basically need a way to load an IFilter and use it no matter what its threading model or our threading model is. See this and this for some examples. I researched this issue for some time, and I believe I found what the problem is. It seems Adobe forgot or not.. Since a filter is implemented as a COM object, it should export this function to let COM know when it can unload this library.

It seems that this causes problems for C applications because the. In the current implementation, this workaround is not needed. How my implementation solves these issues? Instead, you can simply use the reader to get a buffer at a time. If you still want to get the entire text as a string, use the ReadToEnd method. This has the following implications and assumptions: I needed to find the correct COM class that implements the filter for a specific file type.

If you find a filter that behaves badly when used this way, please let me know. To conclude: We solve issue 2 and issue 3 by bypassing COM. This was a simple task, thanks to the excellent RegMon utility from SysInternals. I simply called LoadIFilter and traced which registry keys where read during that operation. I then used the same logic in my own implementation.

The details can be found in the FilterLoader class. During the research I made on how LoadIFilter works, I came across a utility called IFilter Explorer that shows which filters are installed on your computer. From that tool, I also learned that some indexing engines use methods not implemented in LoadIFilter to find filters. One of these methods uses the content type registered for that extension. My version of LoadIFilter also handles loading filters for files that have no filter registered for them but do have a filter registered for their content type.

Loading the DLL and instantiating the filter implementation OK, so we have the name of the DLL and the ID of the class implementing our filter, how do we create an instance of that class?

Most of the work is handled by the ComHelper class. Use Marshal. GetDelegateForFunctionPointer to convert that function pointer to a delegate. Note: this is only available in. NET 2. For an equivalent method in. NET 1. Init iflags, 0, IntPtr. No need to mark your thread as [STAThread] when using filters this is a problem especially with web applications.

The Adobe PDF filter does not crash at the end of the application. Better scalability when dealing with large files. Better filter search logic than LoadIFilter using content type. Once filter DLLs are loaded into your application, they will stay loaded. No COM protection for multi-threaded access to filters Yeah, so? An In-depth Look at the.

I-Filters - Extracting text using the IFilter. See the comments for the problems users encountered with IFilters. Adobe PDF filter threading issues - Information from Adobe about setting the threading model for their v5 filter.

IFilter Explorer - An excellent tool to show you which filters are registered on your computer.

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EPOCALIPSE IFILTER PDF

Surviving three apocalypses in two years was so exhausting that I managed to miss three others. For an equivalent method in. So here is an example:. Post as a guest Name. Once filter DLLs are loaded into your application, they will stay loaded. Using IFilter in C It gives proper output of the value no matter what is displayed. We solve issue 2 and issue 3 by bypassing COM.

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Die iFilter-PDF-Suche funktioniert unter Windows 8 (64 Bit) nicht.

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