OCR Supermarket Receipts in C# (Developer Tutorial)

Receipts and Automation

Receipts are essential in today's fast-paced world. Whether you're buying groceries or dining in a restaurant, a receipt helps track the amount spent and can assist in budgeting. Meanwhile, grocery stores may use receipt scanners to analyze sales data, aiding them in forecasting demand.

However, receipts can be difficult to read, and it can be unclear how totals are calculated. Manual data entry from receipts for budgeting purposes is tedious and error-prone, especially when many items are involved. Losing a receipt can suddenly make it unclear why you exceeded your monthly budget.

To address this problem, budgeting and financial apps have adopted OCR (Optical Character Recognition) technology. By scanning receipts and converting them into digital format, OCR minimizes human error, automates data entry, tracks expenses, and provides insights into purchasing behavior.

OCR technology works by using machine learning algorithms to identify and extract text and numbers from images. However, OCR systems are not perfect, especially when dealing with images affected by noise, such as blurring or smudges, which can lead to incorrect data extraction. Thus, selecting a reliable OCR library that can efficiently process and optimize reading methods is crucial.

Why IronOCR?

IronOCR is a C# library based on a customized version of the Tesseract OCR engine. Here are some of its key features:

1. Cross-Compatibility: Fully compatible with .NET platforms, including .NET 8, 7, 6, 5, and Framework 4.6.2 onwards. It supports Windows, macOS, Azure, and Linux.
2. Flexibility and Scalability: Handles various input formats like jpg, png, and gif. It integrates smoothly with native "System.Drawing" objects in C#.
3. Ease of Use and Support: Well-documented, with a robust API and 24/5 support available.
4. Multi-Language Capabilities: Supports up to 125 languages, ideal for international documents. It excels at recognizing product names and prices, essential for receipt processing.

Implementing Receipt OCR

License Key

Before using IronOCR, obtain a license key. A free trial is available here.

// Replace the license key variable with the trial key you obtained
IronOcr.License.LicenseKey = "REPLACE-WITH-YOUR-KEY";

// Replace the license key variable with the trial key you obtained
IronOcr.License.LicenseKey = "REPLACE-WITH-YOUR-KEY";

' Replace the license key variable with the trial key you obtained
IronOcr.License.LicenseKey = "REPLACE-WITH-YOUR-KEY"

Example: Reading a Supermarket Receipt

Let's explore how IronOCR can be used in an app to scan supermarket receipts with a smartphone, extracting data like product names and prices to reward points based on total purchases.

Input Image

C# Code Implementation

using IronOcr;

class ReceiptScanner
{
    static void Main()
    {
        // Set the license key for IronOCR
        IronOcr.License.LicenseKey = "YOUR-KEY";

        // Instantiate OCR engine
        var ocr = new IronTesseract();

        using var inputPhoto = new OcrInput();
        inputPhoto.LoadImage("supermarketexample.jpg");

        // Perform OCR on the loaded image
        OcrResult result = ocr.Read(inputPhoto);

        // Output the text extracted from the receipt
        string text = result.Text;
        Console.WriteLine(text);
    }
}

using IronOcr;

class ReceiptScanner
{
    static void Main()
    {
        // Set the license key for IronOCR
        IronOcr.License.LicenseKey = "YOUR-KEY";

        // Instantiate OCR engine
        var ocr = new IronTesseract();

        using var inputPhoto = new OcrInput();
        inputPhoto.LoadImage("supermarketexample.jpg");

        // Perform OCR on the loaded image
        OcrResult result = ocr.Read(inputPhoto);

        // Output the text extracted from the receipt
        string text = result.Text;
        Console.WriteLine(text);
    }
}

Imports IronOcr

Friend Class ReceiptScanner
	Shared Sub Main()
		' Set the license key for IronOCR
		IronOcr.License.LicenseKey = "YOUR-KEY"

		' Instantiate OCR engine
		Dim ocr = New IronTesseract()

		Dim inputPhoto = New OcrInput()
		inputPhoto.LoadImage("supermarketexample.jpg")

		' Perform OCR on the loaded image
		Dim result As OcrResult = ocr.Read(inputPhoto)

		' Output the text extracted from the receipt
		Dim text As String = result.Text
		Console.WriteLine(text)
	End Sub
End Class

1. Import the IronOcr library.
2. Instantiate the OCR engine (IronTesseract).
3. Create a new OcrInput to load the image of the receipt.
4. Use the Read method from IronTesseract to extract text.
5. Output the results to the console.

Debugging and Confidence Testing

To ensure consistency, verify the extracted data's confidence level, which determines its accuracy.

OcrResult result = ocr.Read(inputPhoto);
string text = result.Text;
Console.WriteLine(text);
Console.WriteLine($"Confidence: {result.Confidence}");

OcrResult result = ocr.Read(inputPhoto);
string text = result.Text;
Console.WriteLine(text);
Console.WriteLine($"Confidence: {result.Confidence}");

Dim result As OcrResult = ocr.Read(inputPhoto)
Dim text As String = result.Text
Console.WriteLine(text)
Console.WriteLine($"Confidence: {result.Confidence}")

The Confidence property provides a statistical accuracy measure. It ranges from 0 (low confidence) to 1 (high confidence). Adjust your data handling strategies based on these confidence levels for reliability.

Noise Removal and Filtering

Before processing images, use these methods to clean and prepare images for better OCR results:

inputPhoto.DeNoise();      // Removes noise from the image
inputPhoto.ToGrayScale();  // Converts image to grayscale

inputPhoto.DeNoise();      // Removes noise from the image
inputPhoto.ToGrayScale();  // Converts image to grayscale

inputPhoto.DeNoise() ' Removes noise from the image
inputPhoto.ToGrayScale() ' Converts image to grayscale

These preprocessing steps help increase the accuracy of data extraction.

Conclusion

Receipt OCR technology is an asset for businesses and individuals, aiding in budgeting, preventing fraud by verifying transaction details, and automating data collection. IronOCR stands out for its accuracy, speed, and ease of integration with existing platforms, making it an excellent choice for developers aiming to implement receipt scanning solutions.

Try IronOCR's trial license to explore its capabilities.