どのTesseract OCRライブラリを選ぶべきか？開発者によるトップ3オプションの比較

using Veryfi;

public class VeryfiReceiptService
{
    private readonly VeryfiClient _client;

    public VeryfiReceiptService(string clientId, string clientSecret,
                                string username, string apiKey)
    {
        // Four credentials required — four secrets to manage
        _client = new VeryfiClient(clientId, clientSecret, username, apiKey);
    }

    public async Task<ReceiptData> ProcessReceiptAsync(string imagePath)
    {
        // Receipt image leaves your infrastructure here

        var imageBytes = File.ReadAllBytes(imagePath);
        var base64Image = Convert.ToBase64String(imageBytes);

        var response = await _client.ProcessDocumentAsync(
            fileData: base64Image,
            fileName: Path.GetFileName(imagePath)
        );

        return new ReceiptData
        {
            VendorName   = response.Vendor?.Name,
            Total        = response.Total,
            Date         = response.Date,
            Tax          = response.Tax,
            PaymentType  = response.Payment?.Type,
            CardLastFour = response.Payment?.Last4,
            LineItems    = response.LineItems?.Select(li => new LineItem
            {
                Description = li.Description,
                Quantity    = li.Quantity,
                UnitPrice   = li.UnitPrice,
                Total       = li.Total
            }).ToList()
        };
    }
}

Imports Veryfi
Imports System.IO
Imports System.Threading.Tasks

Public Class VeryfiReceiptService
    Private ReadOnly _client As VeryfiClient

    Public Sub New(clientId As String, clientSecret As String, username As String, apiKey As String)
        ' Four credentials required — four secrets to manage
        _client = New VeryfiClient(clientId, clientSecret, username, apiKey)
    End Sub

    Public Async Function ProcessReceiptAsync(imagePath As String) As Task(Of ReceiptData)
        ' Receipt image leaves your infrastructure here

        Dim imageBytes = File.ReadAllBytes(imagePath)
        Dim base64Image = Convert.ToBase64String(imageBytes)

        Dim response = Await _client.ProcessDocumentAsync(
            fileData:=base64Image,
            fileName:=Path.GetFileName(imagePath)
        )

        Return New ReceiptData With {
            .VendorName = response.Vendor?.Name,
            .Total = response.Total,
            .Date = response.Date,
            .Tax = response.Tax,
            .PaymentType = response.Payment?.Type,
            .CardLastFour = response.Payment?.Last4,
            .LineItems = response.LineItems?.Select(Function(li) New LineItem With {
                .Description = li.Description,
                .Quantity = li.Quantity,
                .UnitPrice = li.UnitPrice,
                .Total = li.Total
            }).ToList()
        }
    End Function
End Class

public async Task<InvoiceData> ProcessInvoiceAsync(string pdfPath)
{
    var pdfBytes = File.ReadAllBytes(pdfPath);

    // Invoice uploaded to ベリーフィ — banking details included
    var response = await _client.ProcessDocumentAsync(
        fileData: pdfBytes,
        fileName: Path.GetFileName(pdfPath),
        categories: new[] { "invoices" }
    );

    return new InvoiceData
    {
        InvoiceNumber    = response.InvoiceNumber,
        VendorName       = response.Vendor?.Name,
        VendorTaxId      = response.Vendor?.TaxId,       // transmitted
        Total            = response.Total,
        DueDate          = response.DueDate,
        PaymentTerms     = response.PaymentTerms,
        BankAccountNumber = response.BankAccount?.AccountNumber, // transmitted
        BankRoutingNumber = response.BankAccount?.RoutingNumber  // transmitted
    };
}

Imports System.IO
Imports System.Threading.Tasks

Public Async Function ProcessInvoiceAsync(pdfPath As String) As Task(Of InvoiceData)
    Dim pdfBytes = File.ReadAllBytes(pdfPath)

    ' Invoice uploaded to ベリーフィ — banking details included
    Dim response = Await _client.ProcessDocumentAsync(
        fileData:=pdfBytes,
        fileName:=Path.GetFileName(pdfPath),
        categories:=New String() {"invoices"}
    )

    Return New InvoiceData With {
        .InvoiceNumber = response.InvoiceNumber,
        .VendorName = response.Vendor?.Name,
        .VendorTaxId = response.Vendor?.TaxId,       ' transmitted
        .Total = response.Total,
        .DueDate = response.DueDate,
        .PaymentTerms = response.PaymentTerms,
        .BankAccountNumber = response.BankAccount?.AccountNumber, ' transmitted
        .BankRoutingNumber = response.BankAccount?.RoutingNumber  ' transmitted
    }
End Function

// 銀行取引明細書の処理 — critical sensitivity
public async Task<BankStatementData> ProcessBankStatementAsync(string pdfPath)
{
    var pdfBytes = File.ReadAllBytes(pdfPath);

    // AT THIS POINT: full financial history leaves your infrastructure
    // Account numbers, transaction history, balances — all transmitted
    var response = await _client.ProcessDocumentAsync(
        fileData: pdfBytes,
        categories: new[] { "bank_statements" }
    );

    return new BankStatementData
    {
        AccountNumber  = response.AccountNumber,  // critical — transmitted
        RoutingNumber  = response.RoutingNumber,  // critical — transmitted
        OpeningBalance = response.OpeningBalance,
        ClosingBalance = response.ClosingBalance,
        Transactions   = response.Transactions?.Select(t => new Transaction
        {
            Date        = t.Date,
            Description = t.Description,
            Amount      = t.Amount,
            Balance     = t.RunningBalance
        }).ToList()
    };
}

Imports System.IO
Imports System.Threading.Tasks

' 銀行取引明細書の処理 — critical sensitivity
Public Async Function ProcessBankStatementAsync(pdfPath As String) As Task(Of BankStatementData)
    Dim pdfBytes = File.ReadAllBytes(pdfPath)

    ' AT THIS POINT: full financial history leaves your infrastructure
    ' Account numbers, transaction history, balances — all transmitted
    Dim response = Await _client.ProcessDocumentAsync(
        fileData:=pdfBytes,
        categories:=New String() {"bank_statements"}
    )

    Return New BankStatementData With {
        .AccountNumber = response.AccountNumber,  ' critical — transmitted
        .RoutingNumber = response.RoutingNumber,  ' critical — transmitted
        .OpeningBalance = response.OpeningBalance,
        .ClosingBalance = response.ClosingBalance,
        .Transactions = If(response.Transactions?.Select(Function(t) New Transaction With {
            .Date = t.Date,
            .Description = t.Description,
            .Amount = t.Amount,
            .Balance = t.RunningBalance
        }).ToList(), Nothing)
    }
End Function

using IronOcr;
using System.Text.RegularExpressions;

IronOcr.License.LicenseKey = "YOUR-LICENSE-KEY";

public class LocalFinancialDocumentProcessor
{
    private readonly IronTesseract _ocr = new IronTesseract();

    public BankStatementResult ProcessBankStatement(string pdfPath)
    {
        // All processing on your infrastructure
        // なし network calls — no external access
        using var input = new OcrInput();
        input.LoadPdf(pdfPath);

        var result = _ocr.Read(input);
        var text   = result.Text;

        // Account numbers stay on your server
        return new BankStatementResult
        {
            AccountNumber = ExtractAccountNumber(text),
            Balance       = ExtractBalance(text),
            RawText       = text,
            Confidence    = result.Confidence
        };
    }

    private string ExtractAccountNumber(string text)
    {
        var match = Regex.Match(text,
            @"Account\s*#?\s*:?\s*(\d{4,})",
            RegexOptions.IgnoreCase);
        return match.Success ? match.Groups[1].Value : null;
    }

    private decimal? ExtractBalance(string text)
    {
        var match = Regex.Match(text,
            @"Balance:?\s*\$?([\d,]+\.?\d*)",
            RegexOptions.IgnoreCase);
        if (match.Success && decimal.TryParse(
            match.Groups[1].Value.Replace(",", ""), out var bal))
            return bal;
        return null;
    }
}

Imports IronOcr
Imports System.Text.RegularExpressions

IronOcr.License.LicenseKey = "YOUR-LICENSE-KEY"

Public Class LocalFinancialDocumentProcessor
    Private ReadOnly _ocr As New IronTesseract()

    Public Function ProcessBankStatement(pdfPath As String) As BankStatementResult
        ' All processing on your infrastructure
        ' なし network calls — no external access
        Using input As New OcrInput()
            input.LoadPdf(pdfPath)

            Dim result = _ocr.Read(input)
            Dim text = result.Text

            ' Account numbers stay on your server
            Return New BankStatementResult With {
                .AccountNumber = ExtractAccountNumber(text),
                .Balance = ExtractBalance(text),
                .RawText = text,
                .Confidence = result.Confidence
            }
        End Using
    End Function

    Private Function ExtractAccountNumber(text As String) As String
        Dim match = Regex.Match(text,
            "Account\s*#?\s*:?\s*(\d{4,})",
            RegexOptions.IgnoreCase)
        Return If(match.Success, match.Groups(1).Value, Nothing)
    End Function

    Private Function ExtractBalance(text As String) As Decimal?
        Dim match = Regex.Match(text,
            "Balance:?\s*\$?([\d,]+\.?\d*)",
            RegexOptions.IgnoreCase)
        If match.Success AndAlso Decimal.TryParse(
            match.Groups(1).Value.Replace(",", ""), bal) Then
            Return bal
        End If
        Return Nothing
    End Function
End Class

// Veryfi: works for invoices, fails for shipping manifests
var invoiceResponse = await _client.ProcessDocumentAsync(
    fileData: invoiceBytes,
    categories: new[] { "invoices" }
);

// For anything outside the supported list, you need a second tool
// Contracts: limited support
// Medical forms: not supported
// Shipping documents: not supported
// Custom forms: paid training required

Imports System.Threading.Tasks

' Veryfi: works for invoices, fails for shipping manifests
Dim invoiceResponse = Await _client.ProcessDocumentAsync(
    fileData:=invoiceBytes,
    categories:=New String() {"invoices"}
)

' For anything outside the supported list, you need a second tool
' Contracts: limited support
' Medical forms: not supported
' Shipping documents: not supported
' Custom forms: paid training required

using IronOcr;

var ocr = new IronTesseract();

// Receipts
var receiptResult = ocr.Read("receipt.jpg");
var receiptTotal  = ExtractTotal(receiptResult.Text);

// Contracts — not in Veryfi's scope
using var contractInput = new OcrInput();
contractInput.LoadPdf("contract.pdf");
var contractResult = ocr.Read(contractInput);
var parties        = ExtractContractParties(contractResult.Text);

// Medical forms — requires HIPAA BAA with Veryfi; stays local with IronOCR
var medicalResult = ocr.Read("patient-intake-form.jpg");
var patientName   = medicalResult.Lines.FirstOrDefault()?.Text;

// Shipping documents
var shipResult    = ocr.Read("bill-of-lading.jpg");
var trackingNum   = ExtractPattern(shipResult.Text, @"Tracking\s*#?\s*:?\s*(\w+)");

Imports IronOcr

Dim ocr As New IronTesseract()

' Receipts
Dim receiptResult = ocr.Read("receipt.jpg")
Dim receiptTotal = ExtractTotal(receiptResult.Text)

' Contracts — not in Veryfi's scope
Using contractInput As New OcrInput()
    contractInput.LoadPdf("contract.pdf")
    Dim contractResult = ocr.Read(contractInput)
    Dim parties = ExtractContractParties(contractResult.Text)
End Using

' Medical forms — requires HIPAA BAA with Veryfi; stays local with IronOCR
Dim medicalResult = ocr.Read("patient-intake-form.jpg")
Dim patientName = medicalResult.Lines.FirstOrDefault()?.Text

' Shipping documents
Dim shipResult = ocr.Read("bill-of-lading.jpg")
Dim trackingNum = ExtractPattern(shipResult.Text, "Tracking\s*#?\s*:?\s*(\w+)")

// This method call costs money — every time
// Costs accumulate with every document processed
var response = await _client.ProcessDocumentAsync(bytes);

' This method call costs money — every time
' Costs accumulate with every document processed
Dim response = Await _client.ProcessDocumentAsync(bytes)

// Configure once at startup — no per-call cost
IronOcr.License.LicenseKey = "YOUR-LICENSE-KEY";

var ocr = new IronTesseract();

// This processes 50,000 documents/month at $0 marginal cost
foreach (var documentPath in documentBatch)
{
    var result = ocr.Read(documentPath);
    ProcessExtractedData(result.Text, result.Lines);
}

Imports IronOcr

' Configure once at startup — no per-call cost
IronOcr.License.LicenseKey = "YOUR-LICENSE-KEY"

Dim ocr As New IronTesseract()

' This processes 50,000 documents/month at $0 marginal cost
For Each documentPath In documentBatch
    Dim result = ocr.Read(documentPath)
    ProcessExtractedData(result.Text, result.Lines)
Next

// ベリーフィ error categories reflect cloud dependencies
public async Task<ReceiptData> ProcessWithHandlingAsync(string path)
{
    try
    {
        var bytes    = File.ReadAllBytes(path);
        var response = await _client.ProcessDocumentAsync(bytes);
        return MapToReceiptData(response);
    }
    catch (VeryfiApiException ex) when (ex.StatusCode == 401)
    {
        // Credential failure — check all four credentials
        throw new Exception("Authentication failed. Verify clientId, clientSecret, username, apiKey.", ex);
    }
    catch (VeryfiApiException ex) when (ex.StatusCode == 402)
    {
        // Plan quota exceeded — processing halted until billing resolved
        throw new Exception("Quota exceeded. Check plan limits and billing.", ex);
    }
    catch (VeryfiApiException ex) when (ex.StatusCode == 429)
    {
        // Rate limited — requires exponential backoff implementation
        throw new Exception("Rate limit exceeded. Implement retry with backoff.", ex);
    }
    catch (VeryfiApiException ex) when (ex.StatusCode == 500)
    {
        // ベリーフィ infrastructure failure — your processing is down
        throw new Exception("Veryfi server error. Processing unavailable.", ex);
    }
}

Imports System.IO
Imports System.Threading.Tasks

Public Async Function ProcessWithHandlingAsync(path As String) As Task(Of ReceiptData)
    Try
        Dim bytes = File.ReadAllBytes(path)
        Dim response = Await _client.ProcessDocumentAsync(bytes)
        Return MapToReceiptData(response)
    Catch ex As VeryfiApiException When ex.StatusCode = 401
        ' Credential failure — check all four credentials
        Throw New Exception("Authentication failed. Verify clientId, clientSecret, username, apiKey.", ex)
    Catch ex As VeryfiApiException When ex.StatusCode = 402
        ' Plan quota exceeded — processing halted until billing resolved
        Throw New Exception("Quota exceeded. Check plan limits and billing.", ex)
    Catch ex As VeryfiApiException When ex.StatusCode = 429
        ' Rate limited — requires exponential backoff implementation
        Throw New Exception("Rate limit exceeded. Implement retry with backoff.", ex)
    Catch ex As VeryfiApiException When ex.StatusCode = 500
        ' ベリーフィ infrastructure failure — your processing is down
        Throw New Exception("Veryfi server error. Processing unavailable.", ex)
    End Try
End Function

using IronOcr;

var ocr = new IronTesseract();

// Synchronous — result immediately available
// なし network, no quota, no rate limits
var result = ocr.Read("receipt.jpg");

Console.WriteLine(result.Text);
Console.WriteLine($"Confidence: {result.Confidence}%");

// Word-level positioning for precise field extraction
foreach (var line in result.Lines)
{
    Console.WriteLine($"Y={line.Y}: {line.Text}");
}

Imports IronOcr

Dim ocr As New IronTesseract()

' Synchronous — result immediately available
' なし network, no quota, no rate limits
Dim result = ocr.Read("receipt.jpg")

Console.WriteLine(result.Text)
Console.WriteLine($"Confidence: {result.Confidence}%")

' Word-level positioning for precise field extraction
For Each line In result.Lines
    Console.WriteLine($"Y={line.Y}: {line.Text}")
Next

using IronOcr;
using System.Text.RegularExpressions;

var ocr    = new IronTesseract();
var result = ocr.Read("receipt.jpg");
var text   = result.Text;

// Vendor: first non-empty line, ordered by Y position
var vendor = result.Lines
    .OrderBy(l => l.Y)
    .Select(l => l.Text.Trim())
    .FirstOrDefault(t => !string.IsNullOrWhiteSpace(t) && t.Length > 3);

// Total: pattern matching against common receipt labels
decimal? total = null;
foreach (var pattern in new[] {
    @"Total:?\s*\$?\s*([\d,]+\.?\d*)",
    @"Grand Total:?\s*\$?\s*([\d,]+\.?\d*)",
    @"Amount Due:?\s*\$?\s*([\d,]+\.?\d*)" })
{
    var match = Regex.Match(text, pattern, RegexOptions.IgnoreCase);
    if (match.Success && decimal.TryParse(
        match.Groups[1].Value.Replace(",", ""), out var t))
    {
        total = t;
        break;
    }
}

// Tax
var taxMatch = Regex.Match(text,
    @"(?:Tax|Sales Tax|VAT):?\s*\$?\s*([\d,]+\.?\d*)",
    RegexOptions.IgnoreCase);

Imports IronOcr
Imports System.Text.RegularExpressions

Dim ocr As New IronTesseract()
Dim result = ocr.Read("receipt.jpg")
Dim text = result.Text

' Vendor: first non-empty line, ordered by Y position
Dim vendor = result.Lines _
    .OrderBy(Function(l) l.Y) _
    .Select(Function(l) l.Text.Trim()) _
    .FirstOrDefault(Function(t) Not String.IsNullOrWhiteSpace(t) AndAlso t.Length > 3)

' Total: pattern matching against common receipt labels
Dim total As Decimal? = Nothing
For Each pattern In {
    "Total:?\s*\$?\s*([\d,]+\.?\d*)",
    "Grand Total:?\s*\$?\s*([\d,]+\.?\d*)",
    "Amount Due:?\s*\$?\s*([\d,]+\.?\d*)"
}
    Dim match = Regex.Match(text, pattern, RegexOptions.IgnoreCase)
    If match.Success AndAlso Decimal.TryParse(match.Groups(1).Value.Replace(",", ""), total) Then
        Exit For
    End If
Next

' Tax
Dim taxMatch = Regex.Match(text,
    "(?:Tax|Sales Tax|VAT):?\s*\$?\s*([\d,]+\.?\d*)",
    RegexOptions.IgnoreCase)

// Preserve async signature during transition
public async Task<ReceiptResult> ProcessReceiptAsync(string path)
{
    // Run IronOCR on a background thread
    return await Task.Run(() =>
    {
        var result = _ocr.Read(path);
        return new ReceiptResult
        {
            Vendor = result.Lines.FirstOrDefault()?.Text,
            Total  = ExtractTotal(result.Text),
            Date   = ExtractDate(result.Text)
        };
    });
}

Imports System.Threading.Tasks

Public Async Function ProcessReceiptAsync(path As String) As Task(Of ReceiptResult)
    ' Run IronOCR on a background thread
    Return Await Task.Run(Function()
                              Dim result = _ocr.Read(path)
                              Return New ReceiptResult With {
                                  .Vendor = result.Lines.FirstOrDefault()?.Text,
                                  .Total = ExtractTotal(result.Text),
                                  .Date = ExtractDate(result.Text)
                              }
                          End Function)
End Function

// Multi-page invoice PDF — all pages processed locally
using var input = new OcrInput();
input.LoadPdf("invoice.pdf");

var result       = new IronTesseract().Read(input);
var invoiceText  = result.Text;
var invoiceNumber = Regex.Match(invoiceText,
    @"Invoice\s*#?\s*:?\s*(\w+[-\w]*)",
    RegexOptions.IgnoreCase).Groups[1].Value;

Imports System.Text.RegularExpressions
Imports IronOcr

' Multi-page invoice PDF — all pages processed locally
Dim input As New OcrInput()
input.LoadPdf("invoice.pdf")

Dim result = New IronTesseract().Read(input)
Dim invoiceText As String = result.Text
Dim invoiceNumber As String = Regex.Match(invoiceText, _
    "Invoice\s*#?\s*:?\s*(\w+[-\w]*)", _
    RegexOptions.IgnoreCase).Groups(1).Value