OCR (Optical Character Recognition) in PDF | ASP.NET C#ByteScout PDF Extractor SDK

OCR (Optical Character Recognition) in PDF | ASP.NET C#

Default.aspx:

VB
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<%@ Page Language="C#" AutoEventWireup="true" CodeBehind="Default.aspx.cs" Inherits="OpticalCharacterRecognition._Default" %>

<!DOCTYPE html PUBLIC "-//W3C//DTD XHTML 1.0 Transitional//EN" "http://www.w3.org/TR/xhtml1/DTD/xhtml1-transitional.dtd">

<html xmlns="http://www.w3.org/1999/xhtml" >
<head runat="server">
    <title>Untitled Page</title>
</head>
<body>
    <form id="form1" runat="server">
    <div>

    </div>
    </form>
</body>
</html>

Default.aspx.cs:

C#
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using System;
using Bytescout.PDFExtractor;

// Before running the example, copy missing *.traineddata files from "Redistributable" folder to "ocrdata" project folder.
// or download from https://github.com/bytescout/ocrdata
// Make sure "Copy to Output Directory" property of each added language file is set to "Copy always".

namespace OpticalCharacterRecognition
{

    /*
    IF YOU SEE TEMPORARY FOLDER ACCESS ERRORS: 

    Temporary folder access is required for web application when you use ByteScout SDK in it.
    If you are getting errors related to the access to temporary folder like "Access to the path 'C:\Windows\TEMP\... is denied" then you need to add permission for this temporary folder to make ByteScout SDK working on that machine and IIS configuration because ByteScout SDK requires access to temp folder to cache some of its data for more efficient work.

    SOLUTION:

    If your IIS Application Pool has "Load User Profile" option enabled the IIS provides access to user's temp folder. Check user's temporary folder

    If you are running Web Application under an impersonated account or IIS_IUSRS group, IIS may redirect all requests into separate temp folder like "c:\temp\".

    In this case
    - check the User or User Group your web application is running under
    - then add permissions for this User or User Group to read and write into that temp folder (c:\temp or c:\windows\temp\ folder)
    - restart your web application and try again

    */

    public partial class _Default : System.Web.UI.Page
    {
        protected void Page_Load(object sender, EventArgs e)
        {
            String inputFile = Server.MapPath(@".\bin\sample_ocr.pdf");

            // Location of language files
            String ocrLanguageDataFolder = Server.MapPath(@".\bin\ocrdata");

            // Create Bytescout.PDFExtractor.TextExtractor instance
            using (TextExtractor extractor = new TextExtractor())
            {
                extractor.RegistrationName = "demo";
                extractor.RegistrationKey = "demo";

                // 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 OCR language data files
                extractor.OCRLanguageDataFolder = ocrLanguageDataFolder;
                // Set OCR language
                extractor.OCRLanguage = "eng"; // "eng" for english, "deu" for German, "fra" for French, "spa" for Spanish etc - according to files in "ocrdata" folder
                // 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 OCRAnalyser class to find an optimal set of image preprocessing 
                // filters for your specific document.
                // See "OCR Analyser" example.


                // Load PDF document
                extractor.LoadDocumentFromFile(inputFile);

                // Write extracted text to output stream
                Response.Clear();
                Response.ContentType = "text/html";

                Response.Write("<pre>");
                // Write extracted text to output stream
                Response.Write(extractor.GetText());
                Response.Write("</pre>");

                Response.End();
            }
        }
    }
}

Web.config:

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<?xml version="1.0"?>

<configuration>
  
    <appSettings/>
    <connectionStrings/>
  
    <system.web>
        <!-- 
            Set compilation debug="true" to insert debugging 
            symbols into the compiled page. Because this 
            affects performance, set this value to true only 
            during development.
        -->
        <compilation debug="true" />
        <!--
            The <authentication> section enables configuration 
            of the security authentication mode used by 
            ASP.NET to identify an incoming user. 
        -->
        <authentication mode="Windows" />
        <!--
            The <customErrors> section enables configuration 
            of what to do if/when an unhandled error occurs 
            during the execution of a request. Specifically, 
            it enables developers to configure html error pages 
            to be displayed in place of a error stack trace.

        <customErrors mode="RemoteOnly" defaultRedirect="GenericErrorPage.htm">
            <error statusCode="403" redirect="NoAccess.htm" />
            <error statusCode="404" redirect="FileNotFound.htm" />
        </customErrors>
        -->
    </system.web>
</configuration>