ByteScout PDF Extractor SDK – VB.NET – OCR (Optical Character Recognition)

ByteScout PDF Extractor SDK – VB.NET – OCR (Optical Character Recognition)

Program.vb

Imports Bytescout.PDFExtractor

' This example demonstrates the use of Optical Character Recognition (OCR) to extract text 
' from scanned PDF documents and raster images.

' To make OCR work you should add the following references to your project:
' "Bytescout.PDFExtractor.dll", "Bytescout.PDFExtractor.OCRExtension.dll".

Class Program

    Friend Shared Sub Main(args As String())

        ' Create Bytescout.PDFExtractor.TextExtractor instance
        Dim extractor As New TextExtractor()
        extractor.RegistrationName = "demo"
        extractor.RegistrationKey = "demo"

        ' Load sample PDF document
        extractor.LoadDocumentFromFile("sample_ocr.pdf")

        ' Enable Optical Character Recognition (OCR)
        ' in .Auto mode (SDK automatically checks if needs to use OCR or not)
        extractor.OCRMode = OCRMode.Auto

        ' Set the location of "tessdata" folder containing language data files
        extractor.OCRLanguageDataFolder = "c:\Program Files\Bytescout PDF Extractor SDK\Redistributable\net2.00\tessdata"
        
        ' Set OCR language
        extractor.OCRLanguage = "eng"  ' "eng" for english, "deu" for German, "fra" for French, "spa" for Spanish etc - according to files in /tessdata
        ' Find more language files at https://github.com/tesseract-ocr/tessdata/tree/3.04.00
        
        ' Set PDF document rendering resolution
        extractor.OCRResolution = 300
        
        
        ' You can also apply various preprocessing filters
        ' to improve the recognition on low-quality scans.
        
        ' Automatically deskew skewed scans
        'extractor.OCRImagePreprocessingFilters.AddDeskew()

        ' Remove vertical or horizontal lines (sometimes helps to avoid OCR engine's page segmentation errors)
        'extractor.OCRImagePreprocessingFilters.AddVerticalLinesRemover()
        'extractor.OCRImagePreprocessingFilters.AddHorizontalLinesRemover()
        
        ' Repair broken letters
        'extractor.OCRImagePreprocessingFilters.AddDilate()

        ' Remove noise
        'extractor.OCRImagePreprocessingFilters.AddMedian()
        
        ' Apply Gamma Correction
        'extractor.OCRImagePreprocessingFilters.AddGammaCorrection()
        
        ' Add Contrast
		' extractor.OCRImagePreprocessingFilters.AddContrast(20)


        ' (!) You can use new OCRAnalyzer class to find an optimal set of image preprocessing 
		' filters for your specific document.
		' See "OCR Analyser" example.


        ' Save extracted text to file
        extractor.SaveTextToFile("output.txt")

        ' Cleanup
		extractor.Dispose()

        ' Open output file in default associated application
        System.Diagnostics.Process.Start("output.txt")

    End Sub
    
End Class

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