開発者向けのOCR自動化ガイド

How Tesseract OCR Automates the OCR Process

1. Image Pre-processing:
   • Tesseract OCR can handle various image formats, including scanned documents and images.
   • Before processing, images may undergo pre-processing techniques like resizing, binarization, or noise reduction to enhance recognition accuracy.
2. Page Layout Analysis:
   • Tesseract performs page layout analysis to identify text regions, columns, and blocks within a document.
   • This analysis helps Tesseract recognize the structure of the document, improving the accuracy of text extraction.
3. Character Recognition:
   • Tesseract employs a combination of neural networks and pattern matching to recognize characters.
   • It supports multiple languages and can be trained for specific fonts or language scripts.
4. Output Formatting:
   • Tesseract outputs recognized text in a structured format, making it easier for further processing or integration into databases and applications.

How to Use Tesseract OCR in Windows

Using Tesseract OCR in Windows involves a few steps. Here's a basic guide:

1. Install Tesseract OCR:

   • Download the Tesseract installer for Windows from the official GitHub UB Mannheim repository: Tesseract OCR exe.
   • Run the installer and follow the on-screen instructions to complete the installation.

   Install Tesseract OCR Windows Application

   • Select the location and remember the path of installation as it will be used later to set in the Path variable.

   Update the path of installation

2. Set Up Environment Variables:

   • Add the Tesseract installation directory to the system's PATH environment variable. This ensures that the Tesseract executable can be accessed from any command prompt window.

   Navigate to Environment Variables

   Accessing PATH environment variable

   Modify PATH environment variable

3. Command-Line Usage:

   • Open a command prompt window and navigate to the directory containing your images or scanned documents.
   • Use the following command to perform OCR on an image and output the result to a text file:

   tesseract input_image.png output_text.txt

   tesseract input_image.png output_text.txt

   SHELL

   Replace input_image.png with the name of your image file and output_text.txt with the desired name for the output text file.

4. Example with Invoice Processing:

   • Let's say you have a folder named Invoices containing multiple invoice images.
   • Open a command prompt and navigate to the directory containing the Invoices folder.
   • Use a loop to process all images in the folder:

   for %i in (Invoices\*.png) do tesseract %i Output\%~ni.txt

   for %i in (Invoices\*.png) do tesseract %i Output\%~ni.txt

   SHELL

   This command processes each image in the Invoices folder and outputs the recognized text into corresponding text files in the Output folder.

Pros

• Accuracy: Tesseract OCR provides high accuracy in recognizing text, making it suitable for various applications.
• Language Support: It supports a wide range of languages, making it versatile for global applications.
• Community Support: Being an open-source project, Tesseract OCR has a large and active community that contributes to its improvement.

Cons

• User Interface: Tesseract OCR is primarily a command-line tool, which might be less user-friendly for those accustomed to graphical interfaces.
• Training Complexity: Training Tesseract for specific fonts or languages can be complex and requires technical expertise.

Pros of IronOCR

• Easy Integration: IronOCR seamlessly integrates into .NET applications, providing a simple and intuitive interface for developers.
• High Accuracy: IronOCR leverages advanced algorithms to achieve high accuracy in text recognition, ensuring reliable data extraction.
• Versatility: It supports a wide range of document formats, including PDFs and images, making it suitable for diverse applications.
• Automatic Correction: IronOCR includes features for the automatic correction of recognized text, minimizing errors in extracted data.

Cons of IronOCR

• Cost: While IronOCR offers a free trial, the full version comes with a cost. However, the investment may be justified by the product's robust features and support.

IronOCR Code Example

Let's consider a scenario where you have a C# application that needs to extract text from an invoice image using IronOCR Tesseract 5 for .NET. Below is a simple code example demonstrating how to achieve this:

using IronOcr;

var ocr = new IronTesseract();

using (var input = new OcrInput())
{
    // Load image from file
    input.LoadImage("invoice_image.png");

    // Load PDF document
    input.AddPdf("invoice_pdf.pdf");

    // Perform OCR and get the result
    OcrResult result = ocr.Read(input);

    // Extract and store text from OCR result
    string text = result.Text;
}

using IronOcr;

var ocr = new IronTesseract();

using (var input = new OcrInput())
{
    // Load image from file
    input.LoadImage("invoice_image.png");

    // Load PDF document
    input.AddPdf("invoice_pdf.pdf");

    // Perform OCR and get the result
    OcrResult result = ocr.Read(input);

    // Extract and store text from OCR result
    string text = result.Text;
}

Imports IronOcr

Private ocr = New IronTesseract()

Using input = New OcrInput()
	' Load image from file
	input.LoadImage("invoice_image.png")

	' Load PDF document
	input.AddPdf("invoice_pdf.pdf")

	' Perform OCR and get the result
	Dim result As OcrResult = ocr.Read(input)

	' Extract and store text from OCR result
	Dim text As String = result.Text
End Using

For more detailed information on OCR automation projects using IronOCR, please visit the tutorial on OCR License Plate in C#.

The IronOCR documentation page serves as a comprehensive resource for developers, offering clear and detailed guidance on integrating, configuring, and optimizing the IronOCR library for seamless OCR automation in .NET applications. With thorough documentation, examples, and API references, developers can efficiently harness the power of IronOCR to enhance text recognition accuracy and streamline document processing workflows.