ABBYY FineReader vs Tesseract：OCR 比较

// OCR.space: what you build before the first line of your actual application
public class OcrSpaceApiClient : IDisposable
{
    private readonly HttpClient _httpClient;
    private readonly string _apiKey;
    private readonly SemaphoreSlim _rateLimiter;
    private const string ApiEndpoint = "https://api.ocr.space/parse/image";
    private const int MaxFileSizeFree = 5 * 1024 * 1024; // 5MB — hard limit on free tier
    private const int RateLimitPerMinute = 60;

    public OcrSpaceApiClient(string apiKey)
    {
        _apiKey = apiKey ?? throw new ArgumentNullException(nameof(apiKey));
        _httpClient = new HttpClient();
        _httpClient.Timeout = TimeSpan.FromSeconds(120);
        _rateLimiter = new SemaphoreSlim(RateLimitPerMinute, RateLimitPerMinute);
    }

    public async Task<OcrResult> ExtractTextFromFileAsync(
        string filePath,
        string language = "eng",
        CancellationToken cancellationToken = default)
    {
        if (!File.Exists(filePath))
            throw new FileNotFoundException("Image file not found", filePath);

        var fileInfo = new FileInfo(filePath);
        if (fileInfo.Length > MaxFileSizeFree)
        {
            throw new InvalidOperationException(
                $"File size {fileInfo.Length / 1024 / 1024}MB exceeds free tier limit of 5MB.");
        }

        await _rateLimiter.WaitAsync(cancellationToken);

        try
        {
            // Document leaves your infrastructure here
            byte[] imageBytes = await File.ReadAllBytesAsync(filePath, cancellationToken);
            string base64Image = Convert.ToBase64String(imageBytes);
            string mimeType = GetMimeType(filePath);

            var formContent = new FormUrlEncodedContent(new[]
            {
                new KeyValuePair<string, string>("apikey", _apiKey),
                new KeyValuePair<string, string>("base64Image", $"data:{mimeType};base64,{base64Image}"),
                new KeyValuePair<string, string>("language", language),
                new KeyValuePair<string, string>("isOverlayRequired", "false"),
                new KeyValuePair<string, string>("filetype", Path.GetExtension(filePath).TrimStart('.')),
                new KeyValuePair<string, string>("detectOrientation", "true"),
                new KeyValuePair<string, string>("scale", "true"),
                new KeyValuePair<string, string>("OCREngine", "2")
            });

            var response = await _httpClient.PostAsync(ApiEndpoint, formContent, cancellationToken);

            if (!response.IsSuccessStatusCode)
            {
                string errorBody = await response.Content.ReadAsStringAsync(cancellationToken);
                throw new OcrSpaceException(
                    $"OCR.space API returned {response.StatusCode}: {errorBody}",
                    (int)response.StatusCode);
            }

            string jsonResponse = await response.Content.ReadAsStringAsync(cancellationToken);
            return ParseOcrResponse(jsonResponse);
        }
        finally
        {
            _ = Task.Run(async () =>
            {
                await Task.Delay(60000 / RateLimitPerMinute);
                _rateLimiter.Release();
            });
        }
    }

    private OcrResult ParseOcrResponse(string jsonResponse)
    {
        using var doc = JsonDocument.Parse(jsonResponse);
        var root = doc.RootElement;

        if (root.TryGetProperty("IsErroredOnProcessing", out var isErrored) && isErrored.GetBoolean())
        {
            string errorMessage = "OCR processing failed";
            if (root.TryGetProperty("ErrorMessage", out var errorMessages))
            {
                // Parse the array of error strings manually
                var messages = new List<string>();
                if (errorMessages.ValueKind == JsonValueKind.Array)
                {
                    foreach (var msg in errorMessages.EnumerateArray())
                        messages.Add(msg.GetString() ?? "Unknown error");
                }
                errorMessage = string.Join("; ", messages);
            }
            throw new OcrSpaceException(errorMessage, 500);
        }

        var result = new OcrResult();

        if (root.TryGetProperty("ParsedResults", out var parsedResults))
        {
            foreach (var parsedResult in parsedResults.EnumerateArray())
            {
                if (parsedResult.TryGetProperty("ParsedText", out var parsedText))
                    result.ParsedText += parsedText.GetString();

                if (parsedResult.TryGetProperty("FileParseExitCode", out var exitCode))
                    result.ExitCodes.Add(exitCode.GetInt32());
            }
        }

        return result;
    }

    private string GetMimeType(string filePath) =>
        Path.GetExtension(filePath).ToLowerInvariant() switch
        {
            ".png"          => "image/png",
            ".jpg" or ".jpeg" => "image/jpeg",
            ".bmp"          => "image/bmp",
            ".tiff" or ".tif" => "image/tiff",
            ".pdf"          => "application/pdf",
            _               => "application/octet-stream"
        };

    public void Dispose()
    {
        _httpClient?.Dispose();
        _rateLimiter?.Dispose();
    }
}

// Custom models — no SDK means you define these yourself
public class OcrResult
{
    public string ParsedText { get; set; } = string.Empty;
    public List<string> Warnings { get; } = new();
    public List<int> ExitCodes { get; } = new();
}

public class OcrSpaceException : Exception
{
    public int StatusCode { get; }
    public OcrSpaceException(string message, int statusCode) : base(message)
        => StatusCode = statusCode;
}

Imports System
Imports System.Collections.Generic
Imports System.IO
Imports System.Net.Http
Imports System.Text.Json
Imports System.Threading
Imports System.Threading.Tasks

' OCR.space: what you build before the first line of your actual application
Public Class OcrSpaceApiClient
    Implements IDisposable

    Private ReadOnly _httpClient As HttpClient
    Private ReadOnly _apiKey As String
    Private ReadOnly _rateLimiter As SemaphoreSlim
    Private Const ApiEndpoint As String = "https://api.ocr.space/parse/image"
    Private Const MaxFileSizeFree As Integer = 5 * 1024 * 1024 ' 5MB — hard limit on free tier
    Private Const RateLimitPerMinute As Integer = 60

    Public Sub New(apiKey As String)
        _apiKey = If(apiKey, Throw New ArgumentNullException(NameOf(apiKey)))
        _httpClient = New HttpClient()
        _httpClient.Timeout = TimeSpan.FromSeconds(120)
        _rateLimiter = New SemaphoreSlim(RateLimitPerMinute, RateLimitPerMinute)
    End Sub

    Public Async Function ExtractTextFromFileAsync(filePath As String, Optional language As String = "eng", Optional cancellationToken As CancellationToken = Nothing) As Task(Of OcrResult)
        If Not File.Exists(filePath) Then
            Throw New FileNotFoundException("Image file not found", filePath)
        End If

        Dim fileInfo = New FileInfo(filePath)
        If fileInfo.Length > MaxFileSizeFree Then
            Throw New InvalidOperationException($"File size {fileInfo.Length \ 1024 \ 1024}MB exceeds free tier limit of 5MB.")
        End If

        Await _rateLimiter.WaitAsync(cancellationToken)

        Try
            ' Document leaves your infrastructure here
            Dim imageBytes As Byte() = Await File.ReadAllBytesAsync(filePath, cancellationToken)
            Dim base64Image As String = Convert.ToBase64String(imageBytes)
            Dim mimeType As String = GetMimeType(filePath)

            Dim formContent = New FormUrlEncodedContent(New KeyValuePair(Of String, String)() {
                New KeyValuePair(Of String, String)("apikey", _apiKey),
                New KeyValuePair(Of String, String)("base64Image", $"data:{mimeType};base64,{base64Image}"),
                New KeyValuePair(Of String, String)("language", language),
                New KeyValuePair(Of String, String)("isOverlayRequired", "false"),
                New KeyValuePair(Of String, String)("filetype", Path.GetExtension(filePath).TrimStart("."c)),
                New KeyValuePair(Of String, String)("detectOrientation", "true"),
                New KeyValuePair(Of String, String)("scale", "true"),
                New KeyValuePair(Of String, String)("OCREngine", "2")
            })

            Dim response = Await _httpClient.PostAsync(ApiEndpoint, formContent, cancellationToken)

            If Not response.IsSuccessStatusCode Then
                Dim errorBody = Await response.Content.ReadAsStringAsync(cancellationToken)
                Throw New OcrSpaceException($"OCR.space API returned {response.StatusCode}: {errorBody}", CInt(response.StatusCode))
            End If

            Dim jsonResponse = Await response.Content.ReadAsStringAsync(cancellationToken)
            Return ParseOcrResponse(jsonResponse)
        Finally
            _ = Task.Run(Async Function()
                             Await Task.Delay(60000 \ RateLimitPerMinute)
                             _rateLimiter.Release()
                         End Function)
        End Try
    End Function

    Private Function ParseOcrResponse(jsonResponse As String) As OcrResult
        Using doc = JsonDocument.Parse(jsonResponse)
            Dim root = doc.RootElement

            If root.TryGetProperty("IsErroredOnProcessing", ByRef isErrored) AndAlso isErrored.GetBoolean() Then
                Dim errorMessage As String = "OCR processing failed"
                If root.TryGetProperty("ErrorMessage", ByRef errorMessages) Then
                    ' Parse the array of error strings manually
                    Dim messages = New List(Of String)()
                    If errorMessages.ValueKind = JsonValueKind.Array Then
                        For Each msg In errorMessages.EnumerateArray()
                            messages.Add(msg.GetString() OrElse "Unknown error")
                        Next
                    End If
                    errorMessage = String.Join("; ", messages)
                End If
                Throw New OcrSpaceException(errorMessage, 500)
            End If

            Dim result = New OcrResult()

            If root.TryGetProperty("ParsedResults", ByRef parsedResults) Then
                For Each parsedResult In parsedResults.EnumerateArray()
                    If parsedResult.TryGetProperty("ParsedText", ByRef parsedText) Then
                        result.ParsedText &= parsedText.GetString()
                    End If

                    If parsedResult.TryGetProperty("FileParseExitCode", ByRef exitCode) Then
                        result.ExitCodes.Add(exitCode.GetInt32())
                    End If
                Next
            End If

            Return result
        End Using
    End Function

    Private Function GetMimeType(filePath As String) As String
        Return Path.GetExtension(filePath).ToLowerInvariant() Select Case
            Case ".png" : Return "image/png"
            Case ".jpg", ".jpeg" : Return "image/jpeg"
            Case ".bmp" : Return "image/bmp"
            Case ".tiff", ".tif" : Return "image/tiff"
            Case ".pdf" : Return "application/pdf"
            Case Else : Return "application/octet-stream"
        End Select
    End Function

    Public Sub Dispose() Implements IDisposable.Dispose
        _httpClient?.Dispose()
        _rateLimiter?.Dispose()
    End Sub
End Class

' Custom models — no SDK means you define these yourself
Public Class OcrResult
    Public Property ParsedText As String = String.Empty
    Public ReadOnly Property Warnings As New List(Of String)()
    Public ReadOnly Property ExitCodes As New List(Of Integer)()
End Class

Public Class OcrSpaceException
    Inherits Exception

    Public ReadOnly Property StatusCode As Integer

    Public Sub New(message As String, statusCode As Integer)
        MyBase.New(message)
        Me.StatusCode = statusCode
    End Sub
End Class

// OCR.space: minimum viable extraction — 50岁以上 lines before business logic
public class OcrSpaceBasicExtraction
{
    private readonly HttpClient _httpClient;
    private readonly string _apiKey;

    public OcrSpaceBasicExtraction(string apiKey)
    {
        _apiKey = apiKey;
        _httpClient = new HttpClient();
    }

    public async Task<string> ExtractText(string imagePath)
    {
        // Read file and encode — document leaves your infrastructure
        byte[] imageBytes = File.ReadAllBytes(imagePath);
        string base64 = Convert.ToBase64String(imageBytes);

        var content = new FormUrlEncodedContent(new[]
        {
            new KeyValuePair<string, string>("apikey", _apiKey),
            new KeyValuePair<string, string>("base64Image", $"data:image/png;base64,{base64}"),
            new KeyValuePair<string, string>("language", "eng")
        });

        // Send to cloud
        var response = await _httpClient.PostAsync(
            "https://api.ocr.space/parse/image", content);

        if (!response.IsSuccessStatusCode)
            throw new Exception($"API error: {response.StatusCode}");

        // Parse JSON manually — no typed models
        string json = await response.Content.ReadAsStringAsync();
        using var doc = JsonDocument.Parse(json);

        return doc.RootElement
            .GetProperty("ParsedResults")[0]
            .GetProperty("ParsedText")
            .GetString() ?? string.Empty;
    }
}

Imports System
Imports System.Net.Http
Imports System.Threading.Tasks
Imports System.IO
Imports System.Collections.Generic
Imports System.Text.Json

Public Class OcrSpaceBasicExtraction
    Private ReadOnly _httpClient As HttpClient
    Private ReadOnly _apiKey As String

    Public Sub New(apiKey As String)
        _apiKey = apiKey
        _httpClient = New HttpClient()
    End Sub

    Public Async Function ExtractText(imagePath As String) As Task(Of String)
        ' Read file and encode — document leaves your infrastructure
        Dim imageBytes As Byte() = File.ReadAllBytes(imagePath)
        Dim base64 As String = Convert.ToBase64String(imageBytes)

        Dim content As New FormUrlEncodedContent(New KeyValuePair(Of String, String)() {
            New KeyValuePair(Of String, String)("apikey", _apiKey),
            New KeyValuePair(Of String, String)("base64Image", $"data:image/png;base64,{base64}"),
            New KeyValuePair(Of String, String)("language", "eng")
        })

        ' Send to cloud
        Dim response As HttpResponseMessage = Await _httpClient.PostAsync(
            "https://api.ocr.space/parse/image", content)

        If Not response.IsSuccessStatusCode Then
            Throw New Exception($"API error: {response.StatusCode}")
        End If

        ' Parse JSON manually — no typed models
        Dim json As String = Await response.Content.ReadAsStringAsync()
        Using doc As JsonDocument = JsonDocument.Parse(json)
            Return doc.RootElement _
                .GetProperty("ParsedResults")(0) _
                .GetProperty("ParsedText") _
                .GetString() OrElse String.Empty
        End Using
    End Function
End Class

// IronOCR: complete implementation
var result = new IronTesseract().Read("invoice.png");
Console.WriteLine(result.Text);

// OCR.space batch: 80岁以上 lines of rate-limit plumbing before actual work
public class OcrSpaceBatchProcessing
{
    private readonly HttpClient _httpClient;
    private readonly string _apiKey;
    private readonly SemaphoreSlim _rateLimiter;

    public OcrSpaceBatchProcessing(string apiKey)
    {
        _apiKey = apiKey;
        _httpClient = new HttpClient();
        _rateLimiter = new SemaphoreSlim(60, 60); // Free tier: 60/minute
    }

    public async Task<Dictionary<string, string>> ProcessBatch(string[] imagePaths)
    {
        var results = new Dictionary<string, string>();

        foreach (var imagePath in imagePaths)
        {
            await _rateLimiter.WaitAsync();

            try
            {
                string text = await ProcessWithRetry(imagePath);
                results[imagePath] = text;
            }
            finally
            {
                _ = Task.Run(async () =>
                {
                    await Task.Delay(1000); // 1 second spacing
                    _rateLimiter.Release();
                });
            }
        }

        return results;
    }

    private async Task<string> ProcessWithRetry(string imagePath, int maxRetries = 3)
    {
        for (int attempt = 0; attempt < maxRetries; attempt++)
        {
            try
            {
                byte[] imageBytes = File.ReadAllBytes(imagePath);
                string base64 = Convert.ToBase64String(imageBytes);

                var content = new FormUrlEncodedContent(new[]
                {
                    new KeyValuePair<string, string>("apikey", _apiKey),
                    new KeyValuePair<string, string>("base64Image", $"data:image/png;base64,{base64}"),
                    new KeyValuePair<string, string>("language", "eng")
                });

                var response = await _httpClient.PostAsync(
                    "https://api.ocr.space/parse/image", content);

                if (response.StatusCode == System.Net.HttpStatusCode.TooManyRequests)
                {
                    // Rate limited — exponential backoff
                    await Task.Delay(TimeSpan.FromSeconds(Math.Pow(2, attempt)));
                    continue;
                }

                response.EnsureSuccessStatusCode();

                string json = await response.Content.ReadAsStringAsync();
                using var doc = JsonDocument.Parse(json);

                return doc.RootElement
                    .GetProperty("ParsedResults")[0]
                    .GetProperty("ParsedText")
                    .GetString() ?? string.Empty;
            }
            catch (HttpRequestException) when (attempt < maxRetries - 1)
            {
                await Task.Delay(TimeSpan.FromSeconds(Math.Pow(2, attempt)));
            }
        }

        throw new Exception($"Failed to process {imagePath} after {maxRetries} attempts");
    }
}

Imports System
Imports System.Collections.Generic
Imports System.IO
Imports System.Net.Http
Imports System.Text.Json
Imports System.Threading
Imports System.Threading.Tasks

Public Class OcrSpaceBatchProcessing
    Private ReadOnly _httpClient As HttpClient
    Private ReadOnly _apiKey As String
    Private ReadOnly _rateLimiter As SemaphoreSlim

    Public Sub New(apiKey As String)
        _apiKey = apiKey
        _httpClient = New HttpClient()
        _rateLimiter = New SemaphoreSlim(60, 60) ' Free tier: 60/minute
    End Sub

    Public Async Function ProcessBatch(imagePaths As String()) As Task(Of Dictionary(Of String, String))
        Dim results As New Dictionary(Of String, String)()

        For Each imagePath In imagePaths
            Await _rateLimiter.WaitAsync()

            Try
                Dim text As String = Await ProcessWithRetry(imagePath)
                results(imagePath) = text
            Finally
                _ = Task.Run(Async Function()
                                 Await Task.Delay(1000) ' 1 second spacing
                                 _rateLimiter.Release()
                             End Function)
            End Try
        Next

        Return results
    End Function

    Private Async Function ProcessWithRetry(imagePath As String, Optional maxRetries As Integer = 3) As Task(Of String)
        For attempt As Integer = 0 To maxRetries - 1
            Try
                Dim imageBytes As Byte() = File.ReadAllBytes(imagePath)
                Dim base64 As String = Convert.ToBase64String(imageBytes)

                Dim content As New FormUrlEncodedContent(New KeyValuePair(Of String, String)() {
                    New KeyValuePair(Of String, String)("apikey", _apiKey),
                    New KeyValuePair(Of String, String)("base64Image", $"data:image/png;base64,{base64}"),
                    New KeyValuePair(Of String, String)("language", "eng")
                })

                Dim response As HttpResponseMessage = Await _httpClient.PostAsync("https://api.ocr.space/parse/image", content)

                If response.StatusCode = System.Net.HttpStatusCode.TooManyRequests Then
                    ' Rate limited — exponential backoff
                    Await Task.Delay(TimeSpan.FromSeconds(Math.Pow(2, attempt)))
                    Continue For
                End If

                response.EnsureSuccessStatusCode()

                Dim json As String = Await response.Content.ReadAsStringAsync()
                Using doc As JsonDocument = JsonDocument.Parse(json)
                    Return doc.RootElement _
                        .GetProperty("ParsedResults")(0) _
                        .GetProperty("ParsedText") _
                        .GetString() OrElse String.Empty
                End Using
            Catch ex As HttpRequestException When attempt < maxRetries - 1
                Await Task.Delay(TimeSpan.FromSeconds(Math.Pow(2, attempt)))
            End Try
        Next

        Throw New Exception($"Failed to process {imagePath} after {maxRetries} attempts")
    End Function
End Class

//IronOCRbatch: 8 lines, no rate limits, no retries needed
public Dictionary<string, string> ProcessBatch(string[] imagePaths)
{
    var results = new Dictionary<string, string>();
    var ocr = new IronTesseract();

    foreach (var imagePath in imagePaths)
    {
        // 否 rate limits, no retries, no cloud dependency
        var result = ocr.Read(imagePath);
        results[imagePath] = result.Text;
    }

    return results;
}

Imports System.Collections.Generic

Public Class IronOCRBatch
    Public Function ProcessBatch(imagePaths As String()) As Dictionary(Of String, String)
        Dim results As New Dictionary(Of String, String)()
        Dim ocr As New IronTesseract()

        For Each imagePath As String In imagePaths
            ' 否 rate limits, no retries, no cloud dependency
            Dim result = ocr.Read(imagePath)
            results(imagePath) = result.Text
        Next

        Return results
    End Function
End Class

// OCR.space PDF: size check required, watermarks on free tier
public async Task<List<string>> ExtractTextFromPdf(string pdfPath)
{
    var pageTexts = new List<string>();

    // Reject before wasting a request quota entry
    var fileInfo = new FileInfo(pdfPath);
    if (fileInfo.Length > 5 * 1024 * 1024)
        throw new InvalidOperationException("File exceeds 5MB free tier limit. Upgrade or split PDF.");

    byte[] pdfBytes = File.ReadAllBytes(pdfPath);
    string base64 = Convert.ToBase64String(pdfBytes);

    var content = new FormUrlEncodedContent(new[]
    {
        new KeyValuePair<string, string>("apikey", _apiKey),
        new KeyValuePair<string, string>("base64Image", $"data:application/pdf;base64,{base64}"),
        new KeyValuePair<string, string>("language", "eng"),
        new KeyValuePair<string, string>("filetype", "PDF"),
        new KeyValuePair<string, string>("isCreateSearchablePdf", "false") // Watermarked on free tier
    });

    var response = await _httpClient.PostAsync("https://api.ocr.space/parse/image", content);

    if (!response.IsSuccessStatusCode)
        throw new Exception($"API error: {response.StatusCode}");

    string json = await response.Content.ReadAsStringAsync();
    using var doc = JsonDocument.Parse(json);

    if (doc.RootElement.TryGetProperty("ParsedResults", out var results))
    {
        foreach (var result in results.EnumerateArray())
        {
            if (result.TryGetProperty("ParsedText", out var text))
                pageTexts.Add(text.GetString() ?? string.Empty);
        }
    }

    return pageTexts;
}

Imports System.IO
Imports System.Net.Http
Imports System.Text.Json
Imports System.Threading.Tasks

Public Class OCRSpaceClient
    Private ReadOnly _apiKey As String
    Private ReadOnly _httpClient As HttpClient

    Public Sub New(apiKey As String, httpClient As HttpClient)
        _apiKey = apiKey
        _httpClient = httpClient
    End Sub

    Public Async Function ExtractTextFromPdf(pdfPath As String) As Task(Of List(Of String))
        Dim pageTexts As New List(Of String)()

        ' Reject before wasting a request quota entry
        Dim fileInfo As New FileInfo(pdfPath)
        If fileInfo.Length > 5 * 1024 * 1024 Then
            Throw New InvalidOperationException("File exceeds 5MB free tier limit. Upgrade or split PDF.")
        End If

        Dim pdfBytes As Byte() = File.ReadAllBytes(pdfPath)
        Dim base64 As String = Convert.ToBase64String(pdfBytes)

        Dim content As New FormUrlEncodedContent(New KeyValuePair(Of String, String)() {
            New KeyValuePair(Of String, String)("apikey", _apiKey),
            New KeyValuePair(Of String, String)("base64Image", $"data:application/pdf;base64,{base64}"),
            New KeyValuePair(Of String, String)("language", "eng"),
            New KeyValuePair(Of String, String)("filetype", "PDF"),
            New KeyValuePair(Of String, String)("isCreateSearchablePdf", "false") ' Watermarked on free tier
        })

        Dim response As HttpResponseMessage = Await _httpClient.PostAsync("https://api.ocr.space/parse/image", content)

        If Not response.IsSuccessStatusCode Then
            Throw New Exception($"API error: {response.StatusCode}")
        End If

        Dim json As String = Await response.Content.ReadAsStringAsync()
        Using doc As JsonDocument = JsonDocument.Parse(json)
            If doc.RootElement.TryGetProperty("ParsedResults", results) Then
                For Each result In results.EnumerateArray()
                    If result.TryGetProperty("ParsedText", text) Then
                        pageTexts.Add(If(text.GetString(), String.Empty))
                    End If
                Next
            End If
        End Using

        Return pageTexts
    End Function
End Class

//IronOCRPDF: native support, no size limit, no watermarks
public List<string> ExtractTextFromPdf(string pdfPath)
{
    var pageTexts = new List<string>();

    using var input = new OcrInput();
    input.LoadPdf(pdfPath); // 否 5MB ceiling

    var result = new IronTesseract().Read(input);

    foreach (var page in result.Pages)
        pageTexts.Add(page.Text);

    return pageTexts;
}

// Generate searchable PDF — no watermarks
public void CreateSearchablePdf(string inputPath, string outputPath)
{
    var result = new IronTesseract().Read(inputPath);
    result.SaveAsSearchablePdf(outputPath);
}

Imports System.Collections.Generic

'IronOCRPDF: native support, no size limit, no watermarks
Public Function ExtractTextFromPdf(pdfPath As String) As List(Of String)
    Dim pageTexts As New List(Of String)()

    Using input As New OcrInput()
        input.LoadPdf(pdfPath) ' 否 5MB ceiling

        Dim result = New IronTesseract().Read(input)

        For Each page In result.Pages
            pageTexts.Add(page.Text)
        Next
    End Using

    Return pageTexts
End Function

' Generate searchable PDF — no watermarks
Public Sub CreateSearchablePdf(inputPath As String, outputPath As String)
    Dim result = New IronTesseract().Read(inputPath)
    result.SaveAsSearchablePdf(outputPath)
End Sub

// Before: OCR.space service (simplified — actual implementation is200+lines)
public class OcrSpaceService : IDisposable
{
    private readonly HttpClient _client = new();
    private readonly string _apiKey;

    public OcrSpaceService(string apiKey) => _apiKey = apiKey;

    public async Task<string> ProcessDocument(string path)
    {
        byte[] bytes = File.ReadAllBytes(path);
        string base64 = Convert.ToBase64String(bytes);

        var content = new FormUrlEncodedContent(new[]
        {
            new KeyValuePair<string, string>("apikey", _apiKey),
            new KeyValuePair<string, string>("base64Image", $"data:image/png;base64,{base64}")
        });

        var response = await _client.PostAsync("https://api.ocr.space/parse/image", content);
        response.EnsureSuccessStatusCode();

        string json = await response.Content.ReadAsStringAsync();
        using var doc = JsonDocument.Parse(json);
        return doc.RootElement.GetProperty("ParsedResults")[0].GetProperty("ParsedText").GetString()!;
    }

    public void Dispose() => _client.Dispose();
}

// After:IronOCRservice — no HttpClient, no JSON, no API key
public class IronOcrService
{
    private readonly IronTesseract _ocr = new();

    public string ProcessDocument(string path)
    {
        return _ocr.Read(path).Text;
    }
    // 否 Dispose — no external connections to close
}

Imports System
Imports System.Net.Http
Imports System.IO
Imports System.Threading.Tasks
Imports System.Collections.Generic
Imports System.Text.Json

' Before: OCR.space service (simplified — actual implementation is 200+ lines)
Public Class OcrSpaceService
    Implements IDisposable

    Private ReadOnly _client As New HttpClient()
    Private ReadOnly _apiKey As String

    Public Sub New(apiKey As String)
        _apiKey = apiKey
    End Sub

    Public Async Function ProcessDocument(path As String) As Task(Of String)
        Dim bytes As Byte() = File.ReadAllBytes(path)
        Dim base64 As String = Convert.ToBase64String(bytes)

        Dim content As New FormUrlEncodedContent(New KeyValuePair(Of String, String)() {
            New KeyValuePair(Of String, String)("apikey", _apiKey),
            New KeyValuePair(Of String, String)("base64Image", $"data:image/png;base64,{base64}")
        })

        Dim response As HttpResponseMessage = Await _client.PostAsync("https://api.ocr.space/parse/image", content)
        response.EnsureSuccessStatusCode()

        Dim json As String = Await response.Content.ReadAsStringAsync()
        Using doc As JsonDocument = JsonDocument.Parse(json)
            Return doc.RootElement.GetProperty("ParsedResults")(0).GetProperty("ParsedText").GetString()
        End Using
    End Function

    Public Sub Dispose() Implements IDisposable.Dispose
        _client.Dispose()
    End Sub
End Class

' After: IronOCR service — no HttpClient, no JSON, no API key
Public Class IronOcrService
    Private ReadOnly _ocr As New IronTesseract()

    Public Function ProcessDocument(path As String) As String
        Return _ocr.Read(path).Text
    End Function
    ' No Dispose — no external connections to close
End Class

// At application startup — once, not per request
IronOcr.License.LicenseKey = Environment.GetEnvironmentVariable("IRONOCR_LICENSE");

' At application startup — once, not per request
IronOcr.License.LicenseKey = Environment.GetEnvironmentVariable("IRONOCR_LICENSE")

using var input = new OcrInput();
input.LoadImage("low-quality-scan.jpg");
input.Deskew();
input.DeNoise();
input.Contrast();
input.Binarize();
input.EnhanceResolution(300);
var result = new IronTesseract().Read(input);

Imports IronOcr

Using input As New OcrInput()
    input.LoadImage("low-quality-scan.jpg")
    input.Deskew()
    input.DeNoise()
    input.Contrast()
    input.Binarize()
    input.EnhanceResolution(300)
    Dim result = New IronTesseract().Read(input)
End Using