Invoice OCR API (Developer Tutorial)

What is IronOCR?

IronOCR, developed by Iron Software, provides comprehensive OCR tools for developers. It uses machine learning and computer vision to extract text from scanned documents, images, and PDFs, enabling automated processing. Its APIs integrate seamlessly with various languages and platforms, reducing manual data entry errors and improving efficiency. Extracted data flows directly into existing systems for analysis and decision-making. Features like image preprocessing, barcode recognition, and flexible file parsing enhance its versatility. IronOCR empowers developers to incorporate robust text recognition into their applications.

The library supports 125 international languages through specialized language packs, making it ideal for global invoice processing. Advanced features include computer vision to find text automatically, particularly useful for invoices with varying layouts. Additionally, IronOCR provides multithreaded processing capabilities to handle high-volume invoice processing efficiently.

What Prerequisites Do I Need?

Before working with IronOCR, ensure these prerequisites are in place:

1. A suitable development environment with an IDE such as Visual Studio installed
2. Basic understanding of C# programming to comprehend and modify code examples effectively
3. IronOCR library installed in your project via NuGet Package Manager or command line

Meeting these prerequisites prepares you to dive into working with IronOCR successfully.

IronOCR provides comprehensive setup guides for Windows, Linux, and macOS. The library supports cloud deployment with specific tutorials for AWS Lambda and Azure Functions.

How Do I Create a New Visual Studio Project?

To begin with IronOCR, first create a new Visual Studio project.

Open Visual Studio, go to Files, hover on New, and click on Project.

New Project

In the new window, select Console Application and click Next.

Console Application

A new window appears. Enter your project name and location, then click Next.

Project Configuration

Finally, select the Target framework and click Create.

Target Framework

Your new Visual Studio project is ready. Let's install IronOCR.

How Do I Install IronOCR?

Two simple methods exist for downloading and installing IronOCR:

1. Using Visual Studio NuGet Package Manager
2. Using Visual Studio Command Line

How Do I Extract Data from Invoices Using IronOCR?

Extract invoice data easily with IronOCR using just a few lines of code. This replaces manual data entry and streamlines your workflow.

Here's an example invoice for text extraction:

The sample invoice

Let's extract all data from this invoice:

using IronOcr;
using System;

// Initialize a new instance of the IronTesseract class
// This is the main OCR engine that will process our invoice
var ocr = new IronTesseract();

// Configure OCR settings for better invoice processing
ocr.Configuration.BlackListCharacters = "~`$#^*_}{]___PROTECTED_LINK_48___ method from ___PROTECTED_LINK_49___ class. Key enhancements include:

- **Image preprocessing**: ___PROTECTED_LINK_50___ corrects tilted scans; ___PROTECTED_LINK_51___ removes artifacts
- **Resolution enhancement**: Setting ___PROTECTED_LINK_52___ improves recognition
- **Character blacklisting**: Prevents common OCR misinterpretations
- **Confidence scoring**: Assesses extraction reliability

!___PROTECTED_LINK_53___
**Invoice Parser**

### How Do I Handle Different Invoice Formats?

Invoice formats vary between vendors, but IronOCR provides flexible solutions:

1. **Template-based**: Define ___PROTECTED_LINK_54___
2. **Computer vision**: Use ___PROTECTED_LINK_55___ to locate text
3. **Table extraction**: Leverage ___PROTECTED_LINK_56___ for line items
4. **Multi-format**: Process ___PROTECTED_LINK_57___, ___PROTECTED_LINK_58___, and ___PROTECTED_LINK_59___

For complex layouts, implement the ___PROTECTED_LINK_60___ which uses machine learning to identify structures automatically.

### What Are Common Extraction Patterns for Invoice Data?

Invoice data follows recognizable patterns extractable using regular expressions with OCR results:

```csharp
using IronOcr;
using System;
using System.Text.`RegularExpressions`;
using System.Collections.Generic;

public class `InvoiceDataExtractor`
{
    private readonly `IronTesseract` ocr;

    public `InvoiceDataExtractor`()
    {
        ocr = new `IronTesseract`();
        // Configure for optimal invoice reading
        `ocr.Configuration`.`ReadBarcodes` = true; // Many invoices include barcodes
        `ocr.Configuration`.`TesseractVersion` = `TesseractVersion`.Tesseract5;
    }

    public `InvoiceData` `ExtractInvoiceData`(string imagePath)
    {
        var invoiceData = new `InvoiceData`();

        using (var input = new `OcrInput`(imagePath))
        {
            // Apply filters for better accuracy
            input.`EnhanceResolution`(300);
            `input.Sharpen`();

            var result = `ocr.Read`(input);
            var text = `result.Text`;

            // Extract invoice number
            invoiceData.`InvoiceNumber` = `ExtractPattern`(text, 
                @"INV[/-]?\d{4}[/-]?\d{5}|Invoice\s*#?\s*:?\s*(\d+)");

            // Extract dates
            invoiceData.`InvoiceDate` = `ExtractDate`(text, 
                @"Invoice\s*Date\s*:?\s*(\d{1,2}[/-]\d{1,2}[/-]\d{2,4})");
            invoiceData.`DueDate` = `ExtractDate`(text, 
                @"Due\s*Date\s*:?\s*(\d{1,2}[/-]\d{1,2}[/-]\d{2,4})");

            // Extract amounts
            `invoiceData.Total` = `ExtractAmount`(text, 
                @"Total\s*:?\s*\$?\s*([\d,]+\.?\d*)");
            `invoiceData.Tax` = `ExtractAmount`(text, 
                @"Tax\s*:?\s*\$?\s*([\d,]+\.?\d*)");

            // Extract vendor information
            invoiceData.`VendorName` = `ExtractVendorName`(text);

            // Extract line items using table detection
            invoiceData.`LineItems` = `ExtractLineItems`(result);

            // Extract any barcodes found
            if (`result.Barcodes`.Length > 0)
            {
                invoiceData.`BarcodeValues` = new List<string>();
                foreach (var barcode in `result.Barcodes`)
                {
                    invoiceData.`BarcodeValues`.Add(`barcode.Value`);
                }
            }
        }

        return invoiceData;
    }

    private string `ExtractPattern`(string text, string pattern)
    {
        var match = Regex.Match(text, pattern, `RegexOptions`.`IgnoreCase`);
        return `match.Success` ? `match.Value` : `string.Empty`;
    }

    private `DateTime`? `ExtractDate`(string text, string pattern)
    {
        var match = Regex.Match(text, pattern, `RegexOptions`.`IgnoreCase`);
        if (`match.Success` && `match.Groups`.Count > 1)
        {
            if (`DateTime`.`TryParse`(`match.Groups`[1].Value, out `DateTime` date))
                return date;
        }
        return null;
    }

    private decimal `ExtractAmount`(string text, string pattern)
    {
        var match = Regex.Match(text, pattern, `RegexOptions`.`IgnoreCase`);
        if (`match.Success` && `match.Groups`.Count > 1)
        {
            var amountStr = `match.Groups`[1].Value.Replace(",", "");
            if (decimal.`TryParse`(amountStr, out decimal amount))
                return amount;
        }
        return 0;
    }

    private string `ExtractVendorName`(string text)
    {
        // Usually the vendor name appears in the first few lines
        var lines = `text.Split`('\n');
        if (`lines.Length` > 0)
        {
            // Simple heuristic: first non-empty line that's not a common header
            foreach (var line in lines)
            {
                var trimmed = `line.Trim`();
                if (!string.`IsNullOrEmpty`(trimmed) && 
                    !trimmed.`ToLower`().Contains("invoice") &&
                    `trimmed.Length` > 3)
                {
                    return trimmed;
                }
            }
        }
        return `string.Empty`;
    }

    private List<`LineItem`> `ExtractLineItems`(`OcrResult` result)
    {
        var lineItems = new List<`LineItem`>();

        // Use IronOCR's table detection capabilities
        if (`result.Tables` != null && `result.Tables`.Count > 0)
        {
            foreach (var table in `result.Tables`)
            {
                // Process each row as a potential line item
                for (int i = 1; i < table.`RowCount`; i++) // Skip header row
                {
                    var item = new `LineItem`
                    {
                        Description = table[i, 0]?.Text ?? "",
                        Quantity = `ParseQuantity`(table[i, 1]?.Text),
                        `UnitPrice` = `ParseAmount`(table[i, 2]?.Text),
                        Total = `ParseAmount`(table[i, 3]?.Text)
                    };

                    if (!string.`IsNullOrEmpty`(`item.Description`))
                        `lineItems.Add`(item);
                }
            }
        }

        return lineItems;
    }

    private int `ParseQuantity`(string text)
    {
        if (string.`IsNullOrEmpty`(text)) return 0;
        var cleaned = Regex.Replace(text, @"[^\d]", "");
        return int.`TryParse`(cleaned, out int qty) ? qty : 0;
    }

    private decimal `ParseAmount`(string text)
    {
        if (string.`IsNullOrEmpty`(text)) return 0;
        var cleaned = Regex.Replace(text, @"[^\d.]", "");
        return decimal.`TryParse`(cleaned, out decimal amt) ? amt : 0;
    }
}

// Data classes for structured invoice information
public class `InvoiceData`
{
    public string `InvoiceNumber` { get; set; }
    public `DateTime`? `InvoiceDate` { get; set; }
    public `DateTime`? `DueDate` { get; set; }
    public string `VendorName` { get; set; }
    public decimal Total { get; set; }
    public decimal Tax { get; set; }
    public List<`LineItem`> `LineItems` { get; set; }
    public List<string> `BarcodeValues` { get; set; }
}

public class `LineItem`
{
    public string Description { get; set; }
    public int Quantity { get; set; }
    public decimal `UnitPrice` { get; set; }
    public decimal Total { get; set; }
}

using IronOcr;
using System;

// Initialize a new instance of the IronTesseract class
// This is the main OCR engine that will process our invoice
var ocr = new IronTesseract();

// Configure OCR settings for better invoice processing
ocr.Configuration.BlackListCharacters = "~`$#^*_}{]___PROTECTED_LINK_48___ method from ___PROTECTED_LINK_49___ class. Key enhancements include:

- **Image preprocessing**: ___PROTECTED_LINK_50___ corrects tilted scans; ___PROTECTED_LINK_51___ removes artifacts
- **Resolution enhancement**: Setting ___PROTECTED_LINK_52___ improves recognition
- **Character blacklisting**: Prevents common OCR misinterpretations
- **Confidence scoring**: Assesses extraction reliability

!___PROTECTED_LINK_53___
**Invoice Parser**

### How Do I Handle Different Invoice Formats?

Invoice formats vary between vendors, but IronOCR provides flexible solutions:

1. **Template-based**: Define ___PROTECTED_LINK_54___
2. **Computer vision**: Use ___PROTECTED_LINK_55___ to locate text
3. **Table extraction**: Leverage ___PROTECTED_LINK_56___ for line items
4. **Multi-format**: Process ___PROTECTED_LINK_57___, ___PROTECTED_LINK_58___, and ___PROTECTED_LINK_59___

For complex layouts, implement the ___PROTECTED_LINK_60___ which uses machine learning to identify structures automatically.

### What Are Common Extraction Patterns for Invoice Data?

Invoice data follows recognizable patterns extractable using regular expressions with OCR results:

```csharp
using IronOcr;
using System;
using System.Text.`RegularExpressions`;
using System.Collections.Generic;

public class `InvoiceDataExtractor`
{
    private readonly `IronTesseract` ocr;

    public `InvoiceDataExtractor`()
    {
        ocr = new `IronTesseract`();
        // Configure for optimal invoice reading
        `ocr.Configuration`.`ReadBarcodes` = true; // Many invoices include barcodes
        `ocr.Configuration`.`TesseractVersion` = `TesseractVersion`.Tesseract5;
    }

    public `InvoiceData` `ExtractInvoiceData`(string imagePath)
    {
        var invoiceData = new `InvoiceData`();

        using (var input = new `OcrInput`(imagePath))
        {
            // Apply filters for better accuracy
            input.`EnhanceResolution`(300);
            `input.Sharpen`();

            var result = `ocr.Read`(input);
            var text = `result.Text`;

            // Extract invoice number
            invoiceData.`InvoiceNumber` = `ExtractPattern`(text, 
                @"INV[/-]?\d{4}[/-]?\d{5}|Invoice\s*#?\s*:?\s*(\d+)");

            // Extract dates
            invoiceData.`InvoiceDate` = `ExtractDate`(text, 
                @"Invoice\s*Date\s*:?\s*(\d{1,2}[/-]\d{1,2}[/-]\d{2,4})");
            invoiceData.`DueDate` = `ExtractDate`(text, 
                @"Due\s*Date\s*:?\s*(\d{1,2}[/-]\d{1,2}[/-]\d{2,4})");

            // Extract amounts
            `invoiceData.Total` = `ExtractAmount`(text, 
                @"Total\s*:?\s*\$?\s*([\d,]+\.?\d*)");
            `invoiceData.Tax` = `ExtractAmount`(text, 
                @"Tax\s*:?\s*\$?\s*([\d,]+\.?\d*)");

            // Extract vendor information
            invoiceData.`VendorName` = `ExtractVendorName`(text);

            // Extract line items using table detection
            invoiceData.`LineItems` = `ExtractLineItems`(result);

            // Extract any barcodes found
            if (`result.Barcodes`.Length > 0)
            {
                invoiceData.`BarcodeValues` = new List<string>();
                foreach (var barcode in `result.Barcodes`)
                {
                    invoiceData.`BarcodeValues`.Add(`barcode.Value`);
                }
            }
        }

        return invoiceData;
    }

    private string `ExtractPattern`(string text, string pattern)
    {
        var match = Regex.Match(text, pattern, `RegexOptions`.`IgnoreCase`);
        return `match.Success` ? `match.Value` : `string.Empty`;
    }

    private `DateTime`? `ExtractDate`(string text, string pattern)
    {
        var match = Regex.Match(text, pattern, `RegexOptions`.`IgnoreCase`);
        if (`match.Success` && `match.Groups`.Count > 1)
        {
            if (`DateTime`.`TryParse`(`match.Groups`[1].Value, out `DateTime` date))
                return date;
        }
        return null;
    }

    private decimal `ExtractAmount`(string text, string pattern)
    {
        var match = Regex.Match(text, pattern, `RegexOptions`.`IgnoreCase`);
        if (`match.Success` && `match.Groups`.Count > 1)
        {
            var amountStr = `match.Groups`[1].Value.Replace(",", "");
            if (decimal.`TryParse`(amountStr, out decimal amount))
                return amount;
        }
        return 0;
    }

    private string `ExtractVendorName`(string text)
    {
        // Usually the vendor name appears in the first few lines
        var lines = `text.Split`('\n');
        if (`lines.Length` > 0)
        {
            // Simple heuristic: first non-empty line that's not a common header
            foreach (var line in lines)
            {
                var trimmed = `line.Trim`();
                if (!string.`IsNullOrEmpty`(trimmed) && 
                    !trimmed.`ToLower`().Contains("invoice") &&
                    `trimmed.Length` > 3)
                {
                    return trimmed;
                }
            }
        }
        return `string.Empty`;
    }

    private List<`LineItem`> `ExtractLineItems`(`OcrResult` result)
    {
        var lineItems = new List<`LineItem`>();

        // Use IronOCR's table detection capabilities
        if (`result.Tables` != null && `result.Tables`.Count > 0)
        {
            foreach (var table in `result.Tables`)
            {
                // Process each row as a potential line item
                for (int i = 1; i < table.`RowCount`; i++) // Skip header row
                {
                    var item = new `LineItem`
                    {
                        Description = table[i, 0]?.Text ?? "",
                        Quantity = `ParseQuantity`(table[i, 1]?.Text),
                        `UnitPrice` = `ParseAmount`(table[i, 2]?.Text),
                        Total = `ParseAmount`(table[i, 3]?.Text)
                    };

                    if (!string.`IsNullOrEmpty`(`item.Description`))
                        `lineItems.Add`(item);
                }
            }
        }

        return lineItems;
    }

    private int `ParseQuantity`(string text)
    {
        if (string.`IsNullOrEmpty`(text)) return 0;
        var cleaned = Regex.Replace(text, @"[^\d]", "");
        return int.`TryParse`(cleaned, out int qty) ? qty : 0;
    }

    private decimal `ParseAmount`(string text)
    {
        if (string.`IsNullOrEmpty`(text)) return 0;
        var cleaned = Regex.Replace(text, @"[^\d.]", "");
        return decimal.`TryParse`(cleaned, out decimal amt) ? amt : 0;
    }
}

// Data classes for structured invoice information
public class `InvoiceData`
{
    public string `InvoiceNumber` { get; set; }
    public `DateTime`? `InvoiceDate` { get; set; }
    public `DateTime`? `DueDate` { get; set; }
    public string `VendorName` { get; set; }
    public decimal Total { get; set; }
    public decimal Tax { get; set; }
    public List<`LineItem`> `LineItems` { get; set; }
    public List<string> `BarcodeValues` { get; set; }
}

public class `LineItem`
{
    public string Description { get; set; }
    public int Quantity { get; set; }
    public decimal `UnitPrice` { get; set; }
    public decimal Total { get; set; }
}

using IronOcr;
using System;
using System.Text.`RegularExpressions`;

// Initialize a new instance of the `IronTesseract` class
var ocr = new `IronTesseract`();

// Use the `OcrInput` object to load the image file
using (var input = new `OcrInput`(@"`r2.png`"))
{
    // Perform OCR on the image
    var result = `ocr.Read`(input);

    // Define a regular expression pattern for the invoice number
    var linePattern = @"INV\/\d{4}\/\d{5}";

    // Match the pattern in the extracted text
    var lineMatch = Regex.Match(`result.Text`, linePattern);

    // Check if the pattern matches any part of the text
    if (`lineMatch.Success`)
    {
        // If a match is found, print the invoice number
        var lineValue = `lineMatch.Value`;
        Console.`WriteLine`("Customer Invoice number: " + lineValue);
    }
}

using IronOcr;
using System;
using System.Text.`RegularExpressions`;

// Initialize a new instance of the `IronTesseract` class
var ocr = new `IronTesseract`();

// Use the `OcrInput` object to load the image file
using (var input = new `OcrInput`(@"`r2.png`"))
{
    // Perform OCR on the image
    var result = `ocr.Read`(input);

    // Define a regular expression pattern for the invoice number
    var linePattern = @"INV\/\d{4}\/\d{5}";

    // Match the pattern in the extracted text
    var lineMatch = Regex.Match(`result.Text`, linePattern);

    // Check if the pattern matches any part of the text
    if (`lineMatch.Success`)
    {
        // If a match is found, print the invoice number
        var lineValue = `lineMatch.Value`;
        Console.`WriteLine`("Customer Invoice number: " + lineValue);
    }
}

What Are the Key Benefits of Invoice OCR API?

IronOCR's Invoice OCR API transforms invoice processing through machine learning and computer vision. This technology converts invoice text into machine-readable formats, simplifying data extraction for analysis, integration, and process improvement. It delivers robust automation for invoice processing, improving accuracy and optimizing workflows like accounts payable.

IronOCR offers exceptional accuracy using optimized Tesseract results without additional configuration. It supports multipage frame TIFF, PDF files, and all popular image formats. Barcode reading from images adds another extraction dimension.

Key benefits for invoice processing:

1. Time Savings: Reduce hours to seconds
2. Accuracy: Minimize errors with confidence scoring
3. Scalability: Process thousands with multithreading
4. Integration: Export to searchable PDFs or structured formats
5. Cost Reduction: Lower operational costs

The library's deployment flexibility enables integration into existing systems—on-premises, cloud, or hybrid. With support for Docker, Azure, and AWS, IronOCR scales with your needs.

Production environments benefit from IronOCR's licensing options including dedicated support and regular updates. The library's troubleshooting guides and engineering support ensure smooth implementation.

Visit the homepage for more information on IronOCR. For additional invoice OCR tutorials, see this detailed invoice OCR guide. To learn about using computer vision for invoice fields, check out this computer vision tutorial.