Invoice OCR Open Source Comparison: Find the Best Tool

Optical Character Recognition (OCR) is now a crucial technology for document processing, particularly for invoices. It has evolved significantly, influencing various sectors from education to industry. OCR software reduces the need for manual data entry, and developers can leverage numerous types of Invoice OCR APIs to build software applications for invoice processing.

In this article, we'll explore three open-source C# Invoice OCR software and libraries. We'll also discuss IronOCR, a premium option for developers seeking advanced OCR capabilities in C# projects.

Tesseract OCR

Tesseract OCR, originally developed by Hewlett Packard and now maintained by Google, is a powerful open-source OCR engine. It's capable of handling various document types and converting them into usable data. With support for multiple languages, it's a valuable resource for global businesses.

C# developers find Tesseract OCR particularly useful due to its versatility and accuracy in data extraction. By integrating Tesseract into software applications, developers can efficiently process invoices, extracting pertinent information such as purchase orders and tax amounts. The extracted data can then be used to identify invoice numbers and items from PDF invoices.

Capabilities and Features of Tesseract OCR in C#

Integration in .NET Applications: Integrating Tesseract OCR into C# projects involves using the Tesseract .NET SDK or wrapper. This provides an efficient way to incorporate OCR functionalities while working within the familiar .NET environment.

Text Recognition: Tesseract OCR excels at recognizing and extracting text from various image formats. It's adept at processing a range of document types, from scanned documents and PDF files to images captured in challenging lighting conditions or angles.

Support for Multiple Languages: Tesseract supports over 100 languages, making it incredibly versatile for global applications that process text from diverse linguistic sources.

Customization and Training: Tesseract allows developers to train the engine with new fonts and languages, offering tailored OCR solutions that suit specific business needs or document types.

Emgu CV

Emgu CV C# is a .NET wrapper for the OpenCV library, enabling developers to easily utilize OpenCV's functionalities within C# projects. It provides a rich toolkit for image processing and computer vision, proving useful for processing invoices to extract structured data.

Emgu CV utilizes the Tesseract OCR engine to extract text from images and documents, a critical step for accurate data extraction from invoices. The primary method used is Tesseract.Recognize(), which converts the image text into editable and searchable data.

Advantages of Emgu CV

Cross-Platform: Emgu CV functions on any platform that supports .NET, including iOS, Android, Mac OS, Linux, and Windows.

Cross-Language: Besides C#, Emgu CV is accessible in several languages, including VB.NET, C++, and IronPython, with extensive example code and robust documentation support.

At9T

At9T, also known as (a9t9), offers a free OCR software application that extracts data from PDFs and images using a user-friendly graphical interface. Completely written in C#, it provides an easy way to convert PDFs into searchable documents.

Its intuitive GUI broadens its appeal beyond developers to users seeking simple, one-click solutions. Suitable for both personal and professional use, it efficiently handles various OCR tasks. Users can upload PDF invoices and extract data like invoice dates, line items, and totals with a simple button press.

Features of At9T

User-Friendly Interface: The interface is designed for ease of use, allowing even those with no prior experience to navigate it easily.

Multiple Language Support: Supports various languages, including English, Dutch, Japanese, Korean, and more.

Batch Processing: Capable of processing multiple files simultaneously, saving time when extracting data from numerous documents.

Introducing IronOCR: An Advanced OCR Solution

As discussed, open-source options like Tesseract and Emgu CV can be challenging to integrate without additional components, like wrappers or prior knowledge of OpenCV. Moreover, At9T may not be suitable for complex documents.

To overcome these challenges, IronOCR offers an advanced alternative. As a .NET library, it extends the capabilities of the Tesseract 5 Engine with additional features, and it's easy to integrate into .NET projects.

IronOCR supports various document formats, including PDFs, PNG, JPG, BMP, etc. It operates across many .NET frameworks and platforms, including Windows and macOS, and supports OCR in over 127 languages, making it a global OCR product. It leverages machine learning for superior text recognition.

Key Features of IronOCR

Input Flexibility: Handles various formats like images (JPG, PNG, BMP), multi-page/frame files (TIFF, GIF), System.Drawing objects, streams, and PDFs with optimized DPI.

Advanced Filters: Offers filters for image correction (sharpening, resolution enhancement, etc.) and color correction to ensure optimal quality before OCR.

Region Selection: Allows for specific document regions to be selected for OCR using CropRectangle.

Data Output: Provides data output as .NET text strings, barcodes, QR data, and images.

Structured Data: Outputs structured data by pages, blocks, paragraphs, lines, words, and characters.

Document Export: Enables export as searchable PDFs, HTML, or images.

Text Highlighting & Saving: Features to highlight and save text at various granularities.

Languages & Frameworks: Supports C#, VB.NET, F#, and is compatible with various .NET frameworks.

Operating Systems: Compatible with Windows, macOS, Linux, Docker, Azure, and AWS.

IDE Support: Fully supported on Microsoft Visual Studio and JetBrains ReSharper & Rider.

Example

Below is an example code snippet to extract data from an invoice using IronOCR:

// Create an instance of IronTesseract
var tesseract = new IronTesseract();

// Create an OcrInput object
using (var input = new OcrInput("sample_invoice.png")) // Pass the image path directly to constructor
{
    // Read and store OcrResults object
    var result = tesseract.Read(input);

    // Get all text from the OCR result
    string allText = result.Text;

    // Print the extracted text to the console
    Console.WriteLine(allText);
}

// Create an instance of IronTesseract
var tesseract = new IronTesseract();

// Create an OcrInput object
using (var input = new OcrInput("sample_invoice.png")) // Pass the image path directly to constructor
{
    // Read and store OcrResults object
    var result = tesseract.Read(input);

    // Get all text from the OCR result
    string allText = result.Text;

    // Print the extracted text to the console
    Console.WriteLine(allText);
}

' Create an instance of IronTesseract
Dim tesseract = New IronTesseract()

' Create an OcrInput object
Using input = New OcrInput("sample_invoice.png") ' Pass the image path directly to constructor
	' Read and store OcrResults object
	Dim result = tesseract.Read(input)

	' Get all text from the OCR result
	Dim allText As String = result.Text

	' Print the extracted text to the console
	Console.WriteLine(allText)
End Using

The output data extracted from the invoice image is shown below:

Subsequent data analysis can convert this recognized data into formats such as CSVs for easier handling.

Conclusion

In conclusion, when implementing OCR technology to extract text from images or documents, several options exist. Tesseract OCR, Emgu CV, and At9T are viable open-source tools, each with distinct advantages.

For needs demanding greater sophistication, particularly in invoice OCR, IronOCR offers a robust solution with license options starting at $749.

Whether a programmer wanting to add text-reading capabilities to a project or a business aiming for improved document management, the choice of tool should align with specific needs—considering both free options and more advanced solutions like IronOCR.