从 Azure 计算机视觉 OCR 迁移到

// Azure: endpoint URL + API key + async + nested block traversal — before a single character
var client = new ImageAnalysisClient(new Uri(endpoint), new AzureKeyCredential(apiKey));
using var stream = File.OpenRead(imagePath);
var result = await client.AnalyzeAsync(BinaryData.FromStream(stream), VisualFeatures.Read);
var text = string.Join("\n", result.Value.Read.Blocks.SelectMany(b => b.Lines).Select(l => l.Text));

// IronOCR: no endpoint, no key rotation, no async, no traversal
var text = new IronTesseract().Read(imagePath).Text;

Imports System
Imports System.IO
Imports Azure
Imports Azure.AI.Vision
Imports IronOcr

' Azure: endpoint URL + API key + async + nested block traversal — before a single character
Dim client As New ImageAnalysisClient(New Uri(endpoint), New AzureKeyCredential(apiKey))
Using stream As FileStream = File.OpenRead(imagePath)
    Dim result = Await client.AnalyzeAsync(BinaryData.FromStream(stream), VisualFeatures.Read)
    Dim text As String = String.Join(vbLf, result.Value.Read.Blocks.SelectMany(Function(b) b.Lines).Select(Function(l) l.Text))
End Using

' IronOCR: no endpoint, no key rotation, no async, no traversal
Dim text As String = New IronTesseract().Read(imagePath).Text

dotnet remove package Azure.AI.Vision.ImageAnalysis

dotnet remove package Azure.AI.FormRecognizer

// Before (Azure Computer Vision)
using Azure;
using Azure.AI.Vision.ImageAnalysis;
// For PDF processing:
// using Azure.AI.FormRecognizer.DocumentAnalysis;

// After (IronOCR)
using IronOcr;

Imports IronOcr
' Before (Azure Computer Vision)
' Imports Azure
' Imports Azure.AI.Vision.ImageAnalysis
' For PDF processing:
' Imports Azure.AI.FormRecognizer.DocumentAnalysis

' After (IronOCR)

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

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

IronOcr.License.LicenseKey = Environment.GetEnvironmentVariable("IRONOCR_LICENSE");

Imports System

IronOcr.License.LicenseKey = Environment.GetEnvironmentVariable("IRONOCR_LICENSE")

// appsettings.json binds to this class
public class AzureComputerVisionOptions
{
    public string Endpoint { get; set; }   // "https://your-resource.cognitiveservices.azure.com/"
    public string ApiKey   { get; set; }   // rotated periodically
}

// Program.cs / Startup.cs
services.Configure<AzureComputerVisionOptions>(
    configuration.GetSection("AzureComputerVision"));

services.AddSingleton<ImageAnalysisClient>(sp =>
{
    var opts = sp.GetRequiredService<IOptions<AzureComputerVisionOptions>>().Value;
    return new ImageAnalysisClient(
        new Uri(opts.Endpoint),
        new AzureKeyCredential(opts.ApiKey));
});

services.AddScoped<IOcrService, AzureOcrService>();

' appsettings.json binds to this class
Public Class AzureComputerVisionOptions
    Public Property Endpoint As String   ' "https://your-resource.cognitiveservices.azure.com/"
    Public Property ApiKey As String     ' rotated periodically
End Class

' Program.vb / Startup.vb
services.Configure(Of AzureComputerVisionOptions)(
    configuration.GetSection("AzureComputerVision"))

services.AddSingleton(Of ImageAnalysisClient)(Function(sp)
    Dim opts = sp.GetRequiredService(Of IOptions(Of AzureComputerVisionOptions))().Value
    Return New ImageAnalysisClient(
        New Uri(opts.Endpoint),
        New AzureKeyCredential(opts.ApiKey))
End Function)

services.AddScoped(Of IOcrService, AzureOcrService)()

// AzureOcrService.cs
public class AzureOcrService : IOcrService
{
    private readonly ImageAnalysisClient _client;

    public AzureOcrService(ImageAnalysisClient client)
    {
        _client = client;
    }

    public async Task<string> ReadAsync(string imagePath)
    {
        using var stream = File.OpenRead(imagePath);
        var data = BinaryData.FromStream(stream);
        var result = await _client.AnalyzeAsync(data, VisualFeatures.Read);

        return string.Join("\n",
            result.Value.Read.Blocks
                .SelectMany(b => b.Lines)
                .Select(l => l.Text));
    }
}

Imports System.IO
Imports System.Threading.Tasks

Public Class AzureOcrService
    Implements IOcrService

    Private ReadOnly _client As ImageAnalysisClient

    Public Sub New(client As ImageAnalysisClient)
        _client = client
    End Sub

    Public Async Function ReadAsync(imagePath As String) As Task(Of String) Implements IOcrService.ReadAsync
        Using stream = File.OpenRead(imagePath)
            Dim data = BinaryData.FromStream(stream)
            Dim result = Await _client.AnalyzeAsync(data, VisualFeatures.Read)

            Return String.Join(vbLf, result.Value.Read.Blocks _
                .SelectMany(Function(b) b.Lines) _
                .Select(Function(l) l.Text))
        End Using
    End Function
End Class

// Program.cs / Startup.cs
// One-time license key — no endpoint, no credential class, no options binding
IronOcr.License.LicenseKey = Environment.GetEnvironmentVariable("IRONOCR_LICENSE");

// Register IronTesseract as a singleton — it is thread-safe
services.AddSingleton<IronTesseract>();
services.AddScoped<IOcrService, IronOcrService>();

' Program.vb / Startup.vb
' One-time license key — no endpoint, no credential class, no options binding
IronOcr.License.LicenseKey = Environment.GetEnvironmentVariable("IRONOCR_LICENSE")

' Register IronTesseract as a singleton — it is thread-safe
services.AddSingleton(Of IronTesseract)()
services.AddScoped(Of IOcrService, IronOcrService)()

// IronOcrService.cs
public class IronOcrService : IOcrService
{
    private readonly IronTesseract _ocr;

    public IronOcrService(IronTesseract ocr)
    {
        _ocr = ocr;
    }

    public string Read(string imagePath)
    {
        return _ocr.Read(imagePath).Text;
    }
}

' IronOcrService.vb
Public Class IronOcrService
    Implements IOcrService

    Private ReadOnly _ocr As IronTesseract

    Public Sub New(ocr As IronTesseract)
        _ocr = ocr
    End Sub

    Public Function Read(imagePath As String) As String Implements IOcrService.Read
        Return _ocr.Read(imagePath).Text
    End Function
End Class

// DocumentAnalysisClient — separate from ImageAnalysisClient, separate resource
public class FormRecognizerPdfService
{
    private readonly DocumentAnalysisClient _client;

    public FormRecognizerPdfService(string endpoint, string apiKey)
    {
        _client = new DocumentAnalysisClient(
            new Uri(endpoint),
            new AzureKeyCredential(apiKey));
    }

    // Blocking wait — thread is held for the duration of cloud processing
    public async Task<string> ExtractPdfTextBlocking(string pdfPath)
    {
        using var stream = File.OpenRead(pdfPath);

        var operation = await _client.AnalyzeDocumentAsync(
            WaitUntil.Completed,  // blocks until Azure finishes
            "prebuilt-read",
            stream);

        var docResult = operation.Value;
        var sb = new StringBuilder();
        foreach (var page in docResult.Pages)
        {
            foreach (var line in page.Lines)
            {
                sb.AppendLine(line.Content);  // .Content, not .Text
            }
        }
        return sb.ToString();
    }

    // True async — manual polling loop required
    public async Task<string> ExtractPdfTextNonBlocking(string pdfPath)
    {
        using var stream = File.OpenRead(pdfPath);

        var operation = await _client.AnalyzeDocumentAsync(
            WaitUntil.Started,  // returns immediately, not complete yet
            "prebuilt-read",
            stream);

        // Poll every 500ms until the operation finishes
        while (!operation.HasCompleted)
        {
            await Task.Delay(500);
            await operation.UpdateStatusAsync();
        }

        var docResult = operation.Value;
        var sb = new StringBuilder();
        foreach (var page in docResult.Pages)
        {
            foreach (var line in page.Lines)
            {
                sb.AppendLine(line.Content);
            }
        }
        return sb.ToString();
    }
}

Imports System
Imports System.IO
Imports System.Text
Imports System.Threading.Tasks
Imports Azure
Imports Azure.AI.FormRecognizer.DocumentAnalysis

' DocumentAnalysisClient — separate from ImageAnalysisClient, separate resource
Public Class FormRecognizerPdfService
    Private ReadOnly _client As DocumentAnalysisClient

    Public Sub New(endpoint As String, apiKey As String)
        _client = New DocumentAnalysisClient(
            New Uri(endpoint),
            New AzureKeyCredential(apiKey))
    End Sub

    ' Blocking wait — thread is held for the duration of cloud processing
    Public Async Function ExtractPdfTextBlocking(pdfPath As String) As Task(Of String)
        Using stream = File.OpenRead(pdfPath)
            Dim operation = Await _client.AnalyzeDocumentAsync(
                WaitUntil.Completed,  ' blocks until Azure finishes
                "prebuilt-read",
                stream)

            Dim docResult = operation.Value
            Dim sb = New StringBuilder()
            For Each page In docResult.Pages
                For Each line In page.Lines
                    sb.AppendLine(line.Content)  ' .Content, not .Text
                Next
            Next
            Return sb.ToString()
        End Using
    End Function

    ' True async — manual polling loop required
    Public Async Function ExtractPdfTextNonBlocking(pdfPath As String) As Task(Of String)
        Using stream = File.OpenRead(pdfPath)
            Dim operation = Await _client.AnalyzeDocumentAsync(
                WaitUntil.Started,  ' returns immediately, not complete yet
                "prebuilt-read",
                stream)

            ' Poll every 500ms until the operation finishes
            While Not operation.HasCompleted
                Await Task.Delay(500)
                Await operation.UpdateStatusAsync()
            End While

            Dim docResult = operation.Value
            Dim sb = New StringBuilder()
            For Each page In docResult.Pages
                For Each line In page.Lines
                    sb.AppendLine(line.Content)
                Next
            Next
            Return sb.ToString()
        End Using
    End Function
End Class

// One class handles both images and PDFs — no second client or second resource
public class IronOcrDocumentService
{
    private readonly IronTesseract _ocr;

    public IronOcrDocumentService(IronTesseract ocr)
    {
        _ocr = ocr;
    }

    // Synchronous — returns immediately when local processing completes
    public string ExtractPdfText(string pdfPath)
    {
        using var input = new OcrInput();
        input.LoadPdf(pdfPath);
        return _ocr.Read(input).Text;
    }

    // Specific page range — no per-page billing penalty
    public string ExtractPageRange(string pdfPath, int startPage, int endPage)
    {
        using var input = new OcrInput();
        input.LoadPdfPages(pdfPath, startPage, endPage);
        return _ocr.Read(input).Text;
    }

    // If an async signature is required by an interface or controller
    public Task<string> ExtractPdfTextAsync(string pdfPath)
    {
        return Task.Run(() => ExtractPdfText(pdfPath));
    }
}

Imports System.Threading.Tasks

' One class handles both images and PDFs — no second client or second resource
Public Class IronOcrDocumentService
    Private ReadOnly _ocr As IronTesseract

    Public Sub New(ocr As IronTesseract)
        _ocr = ocr
    End Sub

    ' Synchronous — returns immediately when local processing completes
    Public Function ExtractPdfText(pdfPath As String) As String
        Using input As New OcrInput()
            input.LoadPdf(pdfPath)
            Return _ocr.Read(input).Text
        End Using
    End Function

    ' Specific page range — no per-page billing penalty
    Public Function ExtractPageRange(pdfPath As String, startPage As Integer, endPage As Integer) As String
        Using input As New OcrInput()
            input.LoadPdfPages(pdfPath, startPage, endPage)
            Return _ocr.Read(input).Text
        End Using
    End Function

    ' If an async signature is required by an interface or controller
    Public Function ExtractPdfTextAsync(pdfPath As String) As Task(Of String)
        Return Task.Run(Function() ExtractPdfText(pdfPath))
    End Function
End Class

public async Task<List<WordResult>> ExtractWordPositionsAsync(string imagePath)
{
    using var stream = File.OpenRead(imagePath);
    var imageData = BinaryData.FromStream(stream);

    var response = await _client.AnalyzeAsync(imageData, VisualFeatures.Read);
    var words = new List<WordResult>();

    foreach (var block in response.Value.Read.Blocks)
    {
        foreach (var line in block.Lines)
        {
            foreach (var word in line.Words)
            {
                // BoundingPolygon is a list of ImagePoint — variable vertex count
                var polygon = word.BoundingPolygon;
                int minX = polygon.Min(p => p.X);
                int minY = polygon.Min(p => p.Y);
                int maxX = polygon.Max(p => p.X);
                int maxY = polygon.Max(p => p.Y);

                words.Add(new WordResult
                {
                    Text        = word.Text,
                    // Azure confidence: 0.0 to 1.0 — multiply by 100 for comparison
                    Confidence  = (double)word.Confidence * 100.0,
                    X           = minX,
                    Y           = minY,
                    Width       = maxX - minX,
                    Height      = maxY - minY
                });
            }
        }
    }
    return words;
}

public record WordResult(string Text, double Confidence, int X, int Y, int Width, int Height);

Imports System.IO
Imports System.Threading.Tasks
Imports System.Linq

Public Class ImageAnalyzer
    Private _client As SomeClientType ' Replace with the actual type of _client

    Public Async Function ExtractWordPositionsAsync(imagePath As String) As Task(Of List(Of WordResult))
        Using stream = File.OpenRead(imagePath)
            Dim imageData = BinaryData.FromStream(stream)

            Dim response = Await _client.AnalyzeAsync(imageData, VisualFeatures.Read)
            Dim words = New List(Of WordResult)()

            For Each block In response.Value.Read.Blocks
                For Each line In block.Lines
                    For Each word In line.Words
                        ' BoundingPolygon is a list of ImagePoint — variable vertex count
                        Dim polygon = word.BoundingPolygon
                        Dim minX = polygon.Min(Function(p) p.X)
                        Dim minY = polygon.Min(Function(p) p.Y)
                        Dim maxX = polygon.Max(Function(p) p.X)
                        Dim maxY = polygon.Max(Function(p) p.Y)

                        words.Add(New WordResult With {
                            .Text = word.Text,
                            ' Azure confidence: 0.0 to 1.0 — multiply by 100 for comparison
                            .Confidence = CDbl(word.Confidence) * 100.0,
                            .X = minX,
                            .Y = minY,
                            .Width = maxX - minX,
                            .Height = maxY - minY
                        })
                    Next
                Next
            Next
            Return words
        End Using
    End Function
End Class

Public Class WordResult
    Public Property Text As String
    Public Property Confidence As Double
    Public Property X As Integer
    Public Property Y As Integer
    Public Property Width As Integer
    Public Property Height As Integer
End Class

public List<WordResult> ExtractWordPositions(string imagePath)
{
    var result = new IronTesseract().Read(imagePath);
    var words = new List<WordResult>();

    foreach (var page in result.Pages)
    {
        foreach (var line in page.Lines)
        {
            foreach (var word in line.Words)
            {
                // Rectangle-based bounding box — no polygon math required
                // Confidence is already 0–100, matching the converted Azure scale
                words.Add(new WordResult
                {
                    Text       = word.Text,
                    Confidence = word.Confidence,   // 0–100, no conversion needed
                    X          = word.X,
                    Y          = word.Y,
                    Width      = word.Width,
                    Height     = word.Height
                });
            }
        }
    }
    return words;
}

// Filter to only high-confidence words — common post-processing pattern
public IEnumerable<string> ExtractHighConfidenceWords(string imagePath, double threshold = 80.0)
{
    var result = new IronTesseract().Read(imagePath);
    return result.Words
        .Where(w => w.Confidence >= threshold)
        .Select(w => w.Text);
}

public record WordResult(string Text, double Confidence, int X, int Y, int Width, int Height);

Imports System.Collections.Generic
Imports System.Linq

Public Class WordExtractor

    Public Function ExtractWordPositions(imagePath As String) As List(Of WordResult)
        Dim result = New IronTesseract().Read(imagePath)
        Dim words = New List(Of WordResult)()

        For Each page In result.Pages
            For Each line In page.Lines
                For Each word In line.Words
                    ' Rectangle-based bounding box — no polygon math required
                    ' Confidence is already 0–100, matching the converted Azure scale
                    words.Add(New WordResult With {
                        .Text = word.Text,
                        .Confidence = word.Confidence,   ' 0–100, no conversion needed
                        .X = word.X,
                        .Y = word.Y,
                        .Width = word.Width,
                        .Height = word.Height
                    })
                Next
            Next
        Next

        Return words
    End Function

    ' Filter to only high-confidence words — common post-processing pattern
    Public Function ExtractHighConfidenceWords(imagePath As String, Optional threshold As Double = 80.0) As IEnumerable(Of String)
        Dim result = New IronTesseract().Read(imagePath)
        Return result.Words _
            .Where(Function(w) w.Confidence >= threshold) _
            .Select(Function(w) w.Text)
    End Function

End Class

Public Class WordResult
    Public Property Text As String
    Public Property Confidence As Double
    Public Property X As Integer
    Public Property Y As Integer
    Public Property Width As Integer
    Public Property Height As Integer
End Class

// Azure does not support multi-frame TIFF directly via ImageAnalysisClient
// Must split frames manually and upload each as a separate transaction
public async Task<string> ExtractMultiFrameTiffAsync(string tiffPath)
{
    // Load TIFF using System.Drawing or a third-party library
    using var bitmap = new System.Drawing.Bitmap(tiffPath);
    int frameCount = bitmap.GetFrameCount(
        System.Drawing.Imaging.FrameDimension.Page);

    var allText = new StringBuilder();

    for (int i = 0; i < frameCount; i++)
    {
        // Select frame, save to temporary PNG, upload to Azure
        bitmap.SelectActiveFrame(System.Drawing.Imaging.FrameDimension.Page, i);

        using var ms = new MemoryStream();
        bitmap.Save(ms, System.Drawing.Imaging.ImageFormat.Png);
        ms.Position = 0;

        // Each frame = 1 Azure transaction = $0.001
        var imageData = BinaryData.FromStream(ms);
        var result = await _client.AnalyzeAsync(imageData, VisualFeatures.Read);

        foreach (var block in result.Value.Read.Blocks)
            foreach (var line in block.Lines)
                allText.AppendLine(line.Text);
    }

    return allText.ToString();
}

Imports System.Drawing
Imports System.Drawing.Imaging
Imports System.IO
Imports System.Text
Imports System.Threading.Tasks

Public Class TiffProcessor
    Private _client As ImageAnalysisClient

    Public Async Function ExtractMultiFrameTiffAsync(tiffPath As String) As Task(Of String)
        ' Load TIFF using System.Drawing or a third-party library
        Using bitmap As New Bitmap(tiffPath)
            Dim frameCount As Integer = bitmap.GetFrameCount(FrameDimension.Page)

            Dim allText As New StringBuilder()

            For i As Integer = 0 To frameCount - 1
                ' Select frame, save to temporary PNG, upload to Azure
                bitmap.SelectActiveFrame(FrameDimension.Page, i)

                Using ms As New MemoryStream()
                    bitmap.Save(ms, Imaging.ImageFormat.Png)
                    ms.Position = 0

                    ' Each frame = 1 Azure transaction = $0.001
                    Dim imageData As BinaryData = BinaryData.FromStream(ms)
                    Dim result = Await _client.AnalyzeAsync(imageData, VisualFeatures.Read)

                    For Each block In result.Value.Read.Blocks
                        For Each line In block.Lines
                            allText.AppendLine(line.Text)
                        Next
                    Next
                End Using
            Next

            Return allText.ToString()
        End Using
    End Function
End Class

//IronOCRhandles multi-frame TIFF natively — single call, no frame splitting
public string ExtractMultiFrameTiff(string tiffPath)
{
    using var input = new OcrInput();
    input.LoadImageFrames(tiffPath);  // all frames loaded automatically
    var result = new IronTesseract().Read(input);
    return result.Text;
}

// Access per-page data for frame-level reporting
public void ExtractTiffWithPageStats(string tiffPath)
{
    using var input = new OcrInput();
    input.LoadImageFrames(tiffPath);

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

    Console.WriteLine($"Total frames processed: {result.Pages.Length}");
    foreach (var page in result.Pages)
    {
        Console.WriteLine($"Frame {page.PageNumber}: " +
            $"{page.Words.Length} words, " +
            $"confidence {page.Confidence:F1}%");
    }
}

// Combine with preprocessing for scanned TIFF archives
public string ExtractLowQualityTiffArchive(string tiffPath)
{
    using var input = new OcrInput();
    input.LoadImageFrames(tiffPath);
    input.Deskew();
    input.DeNoise();
    input.Contrast();

    var result = new IronTesseract().Read(input);
    return result.Text;
}

Imports System

' IronOCR handles multi-frame TIFF natively — single call, no frame splitting
Public Function ExtractMultiFrameTiff(tiffPath As String) As String
    Using input As New OcrInput()
        input.LoadImageFrames(tiffPath)  ' all frames loaded automatically
        Dim result = New IronTesseract().Read(input)
        Return result.Text
    End Using
End Function

' Access per-page data for frame-level reporting
Public Sub ExtractTiffWithPageStats(tiffPath As String)
    Using input As New OcrInput()
        input.LoadImageFrames(tiffPath)

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

        Console.WriteLine($"Total frames processed: {result.Pages.Length}")
        For Each page In result.Pages
            Console.WriteLine($"Frame {page.PageNumber}: " &
                              $"{page.Words.Length} words, " &
                              $"confidence {page.Confidence:F1}%")
        Next
    End Using
End Sub

' Combine with preprocessing for scanned TIFF archives
Public Function ExtractLowQualityTiffArchive(tiffPath As String) As String
    Using input As New OcrInput()
        input.LoadImageFrames(tiffPath)
        input.Deskew()
        input.DeNoise()
        input.Contrast()

        Dim result = New IronTesseract().Read(input)
        Return result.Text
    End Using
End Function

// Must throttle to 10 TPS to avoid 429 errors on S1 tier
public class ThrottledAzureBatchProcessor
{
    private readonly ImageAnalysisClient _client;
    // Semaphore limits concurrent Azure calls to stay under 10 TPS
    private readonly SemaphoreSlim _throttle = new SemaphoreSlim(10, 10);

    public async Task<Dictionary<string, string>> ProcessBatchAsync(
        IEnumerable<string> imagePaths)
    {
        var results = new ConcurrentDictionary<string, string>();
        var tasks = imagePaths.Select(async path =>
        {
            await _throttle.WaitAsync();
            try
            {
                using var stream = File.OpenRead(path);
                var data = BinaryData.FromStream(stream);
                var response = await _client.AnalyzeAsync(data, VisualFeatures.Read);

                var text = string.Join("\n",
                    response.Value.Read.Blocks
                        .SelectMany(b => b.Lines)
                        .Select(l => l.Text));

                results[path] = text;

                // Respect 1-second window for the 10 TPS ceiling
                await Task.Delay(100);
            }
            catch (RequestFailedException ex) when (ex.Status == 429)
            {
                // Rate limited despite throttling — back off and retry
                await Task.Delay(2000);
                // Re-queue or log failure — simplified here
                results[path] = string.Empty;
            }
            finally
            {
                _throttle.Release();
            }
        });

        await Task.WhenAll(tasks);
        return new Dictionary<string, string>(results);
    }
}

Imports System.Collections.Concurrent
Imports System.IO
Imports System.Threading
Imports System.Threading.Tasks

' Must throttle to 10 TPS to avoid 429 errors on S1 tier
Public Class ThrottledAzureBatchProcessor
    Private ReadOnly _client As ImageAnalysisClient
    ' Semaphore limits concurrent Azure calls to stay under 10 TPS
    Private ReadOnly _throttle As New SemaphoreSlim(10, 10)

    Public Async Function ProcessBatchAsync(imagePaths As IEnumerable(Of String)) As Task(Of Dictionary(Of String, String))
        Dim results As New ConcurrentDictionary(Of String, String)()
        Dim tasks = imagePaths.Select(Async Function(path)
                                          Await _throttle.WaitAsync()
                                          Try
                                              Using stream = File.OpenRead(path)
                                                  Dim data = BinaryData.FromStream(stream)
                                                  Dim response = Await _client.AnalyzeAsync(data, VisualFeatures.Read)

                                                  Dim text = String.Join(vbLf,
                                                                         response.Value.Read.Blocks _
                                                                         .SelectMany(Function(b) b.Lines) _
                                                                         .Select(Function(l) l.Text))

                                                  results(path) = text

                                                  ' Respect 1-second window for the 10 TPS ceiling
                                                  Await Task.Delay(100)
                                              End Using
                                          Catch ex As RequestFailedException When ex.Status = 429
                                              ' Rate limited despite throttling — back off and retry
                                              Await Task.Delay(2000)
                                              ' Re-queue or log failure — simplified here
                                              results(path) = String.Empty
                                          Finally
                                              _throttle.Release()
                                          End Try
                                      End Function)

        Await Task.WhenAll(tasks)
        Return New Dictionary(Of String, String)(results)
    End Function
End Class

// 否 rate limiting needed — throughput is hardware-bound
public Dictionary<string, string> ProcessBatch(IEnumerable<string> imagePaths)
{
    var results = new ConcurrentDictionary<string, string>();

    Parallel.ForEach(imagePaths, imagePath =>
    {
        // Each thread gets its own IronTesseract instance — fully thread-safe
        var ocr = new IronTesseract();
        var result = ocr.Read(imagePath);
        results[imagePath] = result.Text;
    });

    return new Dictionary<string, string>(results);
}

// With controlled parallelism for memory-constrained environments
public Dictionary<string, string> ProcessBatchControlled(
    IEnumerable<string> imagePaths, int maxDegreeOfParallelism = 4)
{
    var results = new ConcurrentDictionary<string, string>();
    var options = new ParallelOptions { MaxDegreeOfParallelism = maxDegreeOfParallelism };

    Parallel.ForEach(imagePaths, options, imagePath =>
    {
        var ocr = new IronTesseract();
        var result = ocr.Read(imagePath);
        results[imagePath] = result.Text;
    });

    return new Dictionary<string, string>(results);
}

Imports System.Collections.Concurrent
Imports System.Collections.Generic
Imports System.Threading.Tasks

' 否 rate limiting needed — throughput is hardware-bound
Public Function ProcessBatch(imagePaths As IEnumerable(Of String)) As Dictionary(Of String, String)
    Dim results As New ConcurrentDictionary(Of String, String)()

    Parallel.ForEach(imagePaths, Sub(imagePath)
                                     ' Each thread gets its own IronTesseract instance — fully thread-safe
                                     Dim ocr As New IronTesseract()
                                     Dim result = ocr.Read(imagePath)
                                     results(imagePath) = result.Text
                                 End Sub)

    Return New Dictionary(Of String, String)(results)
End Function

' With controlled parallelism for memory-constrained environments
Public Function ProcessBatchControlled(imagePaths As IEnumerable(Of String), Optional maxDegreeOfParallelism As Integer = 4) As Dictionary(Of String, String)
    Dim results As New ConcurrentDictionary(Of String, String)()
    Dim options As New ParallelOptions With {.MaxDegreeOfParallelism = maxDegreeOfParallelism}

    Parallel.ForEach(imagePaths, options, Sub(imagePath)
                                              Dim ocr As New IronTesseract()
                                              Dim result = ocr.Read(imagePath)
                                              results(imagePath) = result.Text
                                          End Sub)

    Return New Dictionary(Of String, String)(results)
End Function

// 否 client-side preprocessing API — must preprocess externally before upload
public async Task<string> ExtractFromLowQualityScanAsync(string imagePath)
{
    // Option 1: Accept whatever Azure returns (may be empty or low-quality)
    using var stream = File.OpenRead(imagePath);
    var imageData = BinaryData.FromStream(stream);

    var result = await _client.AnalyzeAsync(imageData, VisualFeatures.Read);

    // 否 way to know if the server applied enhancement
    // 否 confidence on the overall result — only per-word
    var text = string.Join("\n",
        result.Value.Read.Blocks
            .SelectMany(b => b.Lines)
            .Select(l => l.Text));

    if (string.IsNullOrWhiteSpace(text))
    {
        // Option 2: Apply external preprocessing using System.Drawing, SkiaSharp,
        // or ImageMagick, re-serialize to stream, re-upload — second billable transaction
        throw new Exception("Azure returned empty result; manual preprocessing needed");
    }

    return text;
}

Imports System.IO
Imports System.Threading.Tasks

Public Class Example
    Public Async Function ExtractFromLowQualityScanAsync(imagePath As String) As Task(Of String)
        ' 否 client-side preprocessing API — must preprocess externally before upload
        ' Option 1: Accept whatever Azure returns (may be empty or low-quality)
        Using stream = File.OpenRead(imagePath)
            Dim imageData = BinaryData.FromStream(stream)

            Dim result = Await _client.AnalyzeAsync(imageData, VisualFeatures.Read)

            ' 否 way to know if the server applied enhancement
            ' 否 confidence on the overall result — only per-word
            Dim text = String.Join(vbLf, result.Value.Read.Blocks.SelectMany(Function(b) b.Lines).Select(Function(l) l.Text))

            If String.IsNullOrWhiteSpace(text) Then
                ' Option 2: Apply external preprocessing using System.Drawing, SkiaSharp,
                ' or ImageMagick, re-serialize to stream, re-upload — second billable transaction
                Throw New Exception("Azure returned empty result; manual preprocessing needed")
            End If

            Return text
        End Using
    End Function
End Class

// Preprocessing is part of the same call — no re-upload, no second transaction
public string ExtractFromLowQualityScan(string imagePath)
{
    using var input = new OcrInput();
    input.LoadImage(imagePath);

    // Correct common scanning defects before OCR
    input.Deskew();           // Fix rotated documents
    input.DeNoise();          // Remove scanner noise
    input.Contrast();         // Improve contrast for faded documents
    input.Binarize();         // Convert to black and white

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

    Console.WriteLine($"Confidence after preprocessing: {result.Confidence:F1}%");
    return result.Text;
}

// For severely degraded documents
public string ExtractFromDegradedDocument(string imagePath)
{
    using var input = new OcrInput();
    input.LoadImage(imagePath);
    input.DeepCleanBackgroundNoise();  // Deep learning-based noise removal
    input.Deskew();
    input.Scale(150);                  // Upscale for better character resolution

    var result = new IronTesseract().Read(input);
    return result.Text;
}

Imports System

Public Class OcrProcessor
    ' Preprocessing is part of the same call — no re-upload, no second transaction
    Public Function ExtractFromLowQualityScan(imagePath As String) As String
        Using input As New OcrInput()
            input.LoadImage(imagePath)

            ' Correct common scanning defects before OCR
            input.Deskew()           ' Fix rotated documents
            input.DeNoise()          ' Remove scanner noise
            input.Contrast()         ' Improve contrast for faded documents
            input.Binarize()         ' Convert to black and white

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

            Console.WriteLine($"Confidence after preprocessing: {result.Confidence:F1}%")
            Return result.Text
        End Using
    End Function

    ' For severely degraded documents
    Public Function ExtractFromDegradedDocument(imagePath As String) As String
        Using input As New OcrInput()
            input.LoadImage(imagePath)
            input.DeepCleanBackgroundNoise()  ' Deep learning-based noise removal
            input.Deskew()
            input.Scale(150)                  ' Upscale for better character resolution

            Dim result = New IronTesseract().Read(input)
            Return result.Text
        End Using
    End Function
End Class

// Existing interface — do not change it
public interface IOcrService
{
    Task<string> ReadAsync(string imagePath);
}

// NewIronOCRimplementation — fulfills the contract
public class IronOcrService : IOcrService
{
    private readonly IronTesseract _ocr;

    public IronOcrService(IronTesseract ocr) => _ocr = ocr;

    public Task<string> ReadAsync(string imagePath)
    {
        // Task.Run offloads to thread pool — no await chain needed
        return Task.Run(() => _ocr.Read(imagePath).Text);
    }
}

' Existing interface — do not change it
Public Interface IOcrService
    Function ReadAsync(imagePath As String) As Task(Of String)
End Interface

' NewIronOCRimplementation — fulfills the contract
Public Class IronOcrService
    Implements IOcrService

    Private ReadOnly _ocr As IronTesseract

    Public Sub New(ocr As IronTesseract)
        _ocr = ocr
    End Sub

    Public Function ReadAsync(imagePath As String) As Task(Of String) Implements IOcrService.ReadAsync
        ' Task.Run offloads to thread pool — no await chain needed
        Return Task.Run(Function() _ocr.Read(imagePath).Text)
    End Function
End Class

// Before: Azure threshold (0.0 - 1.0 scale)
var highConfidenceWords = azureWords
    .Where(w => w.Confidence > 0.85f)
    .Select(w => w.Text);

// After:IronOCRthreshold (0 - 100 scale)
var result = new IronTesseract().Read(imagePath);
var highConfidenceWords = result.Words
    .Where(w => w.Confidence > 85.0)
    .Select(w => w.Text);

// Overall document confidence — also on 0-100 scale
if (result.Confidence < 70.0)
{
    // Document may need preprocessing or manual review
}

Imports System.Linq

' Before: Azure threshold (0.0 - 1.0 scale)
Dim highConfidenceWords = azureWords _
    .Where(Function(w) w.Confidence > 0.85F) _
    .Select(Function(w) w.Text)

' After: IronOCR threshold (0 - 100 scale)
Dim result = New IronTesseract().Read(imagePath)
Dim highConfidenceWords = result.Words _
    .Where(Function(w) w.Confidence > 85.0) _
    .Select(Function(w) w.Text)

' Overall document confidence — also on 0-100 scale
If result.Confidence < 70.0 Then
    ' Document may need preprocessing or manual review
End If

var ocr = new IronTesseract();

// Define extraction zones for a known invoice template
var headerZone    = new CropRectangle(50,  40,  400, 60);
var totalZone     = new CropRectangle(350, 600, 250, 50);
var dateZone      = new CropRectangle(400, 100, 200, 40);

string header, total, date;

using (var input = new OcrInput())
{
    input.LoadImage("invoice.jpg", headerZone);
    header = ocr.Read(input).Text.Trim();
}

using (var input = new OcrInput())
{
    input.LoadImage("invoice.jpg", totalZone);
    total = ocr.Read(input).Text.Trim();
}

using (var input = new OcrInput())
{
    input.LoadImage("invoice.jpg", dateZone);
    date = ocr.Read(input).Text.Trim();
}

Imports IronOcr

Dim ocr As New IronTesseract()

' Define extraction zones for a known invoice template
Dim headerZone As New CropRectangle(50, 40, 400, 60)
Dim totalZone As New CropRectangle(350, 600, 250, 50)
Dim dateZone As New CropRectangle(400, 100, 200, 40)

Dim header As String
Dim total As String
Dim date As String

Using input As New OcrInput()
    input.LoadImage("invoice.jpg", headerZone)
    header = ocr.Read(input).Text.Trim()
End Using

Using input As New OcrInput()
    input.LoadImage("invoice.jpg", totalZone)
    total = ocr.Read(input).Text.Trim()
End Using

Using input As New OcrInput()
    input.LoadImage("invoice.jpg", dateZone)
    date = ocr.Read(input).Text.Trim()
End Using

var result = new IronTesseract().Read("document.jpg");

// Write hOCR file — recognized by most document analysis tools
result.SaveAsHocrFile("document.hocr");

// Searchable PDF — alternative for archive and search indexing workflows
result.SaveAsSearchablePdf("document-searchable.pdf");

Dim result = (New IronTesseract()).Read("document.jpg")

' Write hOCR file — recognized by most document analysis tools
result.SaveAsHocrFile("document.hocr")

' Searchable PDF — alternative for archive and search indexing workflows
result.SaveAsSearchablePdf("document-searchable.pdf")

# Remove only the OCR-related Azure packages
dotnet remove package Azure.AI.Vision.ImageAnalysis
dotnet remove package Azure.AI.FormRecognizer

# Verify remaining Azure packages have no new conflicts
dotnet restore
dotnet build

using var input = new OcrInput();
input.LoadImage("low-quality-scan.jpg");
input.Deskew();
input.DeNoise();
input.Scale(200);       // Upscale to improve character resolution
input.Contrast();
input.Sharpen();

var result = new IronTesseract().Read(input);
Console.WriteLine($"Extraction confidence: {result.Confidence:F1}%");

Imports IronOcr

Using input As New OcrInput()
    input.LoadImage("low-quality-scan.jpg")
    input.Deskew()
    input.DeNoise()
    input.Scale(200) ' Upscale to improve character resolution
    input.Contrast()
    input.Sharpen()

    Dim result = New IronTesseract().Read(input)
    Console.WriteLine($"Extraction confidence: {result.Confidence:F1}%")
End Using

# Find all Azure OCR-related using statements
grep -r "Azure.AI.Vision.ImageAnalysis" --include="*.cs" .
grep -r "Azure.AI.FormRecognizer" --include="*.cs" .
grep -r "ImageAnalysisClient" --include="*.cs" .
grep -r "DocumentAnalysisClient" --include="*.cs" .
grep -r "AnalyzeAsync" --include="*.cs" .
grep -r "AnalyzeDocumentAsync" --include="*.cs" .
grep -r "VisualFeatures.Read" --include="*.cs" .
grep -r "WaitUntil.Completed" --include="*.cs" .
grep -r "UpdateStatusAsync" --include="*.cs" .
grep -r "AzureKeyCredential" --include="*.cs" .

grep -r "cognitiveservices.azure.com" --include="*.json" .
grep -r "AzureComputerVision\|FormRecognizer" --include="*.json" .
grep -r "ComputerVision\|FormRecognizer" --include="appsettings*.json" .