Scanned PDF to Text
How to Extract Text from Scanned PDFs in .NET Using Aspose.OCR

How to Extract Text from Scanned PDFs in .NET Using Aspose.OCR

Scanned PDFs are often challenging to work with because they are essentially just images of text. Converting these images into searchable, editable text documents opens up a world of possibilities for document management and content accessibility. With Aspose.OCR for .NET, you can convert scanned PDFs into fully searchable documents while preserving the original images.

Why OCR (Optical Character Recognition) Matters for Scanned PDFs

  1. Data Extraction:
    • OCR lets you convert scanned text into machine-readable data, which can be edited and indexed.
  2. Searchability:
    • By converting scanned PDFs into searchable documents, you can quickly find relevant information without manually searching through pages.
  3. Improved Productivity:
    • Save time by automating the conversion of scanned documents into editable formats like Word or Excel.

Prerequisites: Setting Up for Scanned PDF Text Extraction

Before you begin extracting text from your scanned PDFs, ensure the following steps are complete:

  1. Install Aspose.OCR for .NET:
    • Add Aspose.OCR to your project using NuGet:
      dotnet add package Aspose.OCR
  2. Obtain a Metered License:
    • Set up your metered license to unlock all features of the Aspose.OCR library using SetMeteredKey().
  3. Prepare Your Scanned PDFs:
    • Make sure your scanned PDFs are of high quality. Better quality results in more accurate OCR.

Step-by-Step Guide: Extracting Text from Scanned PDFs

Step 1: Install the Required Library

Start by installing Aspose.OCR for .NET into your project. You can do this directly from NuGet.

dotnet add package Aspose.OCR

Step 2: Set Up Your License Keys

Before proceeding, configure your license for Aspose.OCR to unlock all features.

using Aspose.OCR;

Metered license = new Metered();
license.SetMeteredKey("<your public key>", "<your private key>");
Console.WriteLine("License configured successfully.");

Step 3: Load the Scanned PDF into the OCR Input Object

You’ll need to load the scanned PDF into the OcrInput object. Aspose.OCR supports scanning multiple pages of a PDF.

OcrInput input = new OcrInput(Aspose.OCR.InputType.PDF);
input.Add("scanned_sample.pdf", 0, 3); // Process first 3 pages of the PDF
Console.WriteLine("Scanned PDF loaded successfully.");

Step 4: Process the Scanned PDF Using the OCR Engine

With the PDF loaded, pass it to the Aspose OCR engine for recognition.

Aspose.OCR.AsposeOcr recognitionEngine = new Aspose.OCR.AsposeOcr();
RecognitionSettings settings = new RecognitionSettings();
settings.Language = Aspose.OCR.Language.Latin;  // Set OCR language (e.g., Latin for English)

List<Aspose.OCR.RecognitionResult> results = recognitionEngine.Recognize(input, settings);
Console.WriteLine("Text extracted from PDF.");

Step 5: Output the Recognized Text or Save It

Once the OCR engine processes the PDF, you can either output the recognized text directly or save it to a file.

string recognizedText = results[0].RecognitionText;
Console.WriteLine($"Recognized Text: {recognizedText}");

// Save the result to a text file
results[0].Save("output.txt", Aspose.OCR.SaveFormat.Text);
Console.WriteLine("Recognized text saved to output.txt.");

Step 6: Test and Optimize OCR Results

After extracting the text, test the output for accuracy. If necessary, you can tweak the OCR settings to improve results for different document layouts.

Common Issues and Fixes

1. Poor OCR Accuracy

  • Solution: Ensure that the scanned PDF quality is high. Use high-resolution scans to improve recognition accuracy.

2. Unsupported Fonts

  • Solution: Provide the correct language setting in the OCR options to enhance recognition for non-Latin characters.

3. Slow Performance

  • Solution: Break the PDF into smaller chunks or pages for faster processing, especially for large documents.
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