從 AWS Textract 遷移到 IronOCR

// Textract: five environment variables, an IAM role, and an S3 bucket
// — all required before the first OCR call

// Environment must have:
//   AWS_ACCESS_KEY_ID=AKIA...
//   AWS_SECRET_ACCESS_KEY=...
//   AWS_DEFAULT_REGION=us-east-1
//   IAM role: textract:DetectDocumentText, textract:AnalyzeDocument
//   IAM role: s3:PutObject, s3:DeleteObject (for any PDF processing)
//   S3 bucket: my-textract-staging-bucket (with lifecycle policy to prevent cost accumulation)

public class TextractOcrService
{
    private readonly AmazonTextractClient _textractClient;
    private readonly AmazonS3Client _s3Client; // required for PDFs

    public TextractOcrService()
    {
        // Fails with AmazonClientException if credentials not found in chain
        _textractClient = new AmazonTextractClient(Amazon.RegionEndpoint.USEast1);
        _s3Client = new AmazonS3Client(Amazon.RegionEndpoint.USEast1);
    }
}

Imports Amazon
Imports Amazon.Textract
Imports Amazon.S3

' Textract: five environment variables, an IAM role, and an S3 bucket
' — all required before the first OCR call

' Environment must have:
'   AWS_ACCESS_KEY_ID=AKIA...
'   AWS_SECRET_ACCESS_KEY=...
'   AWS_DEFAULT_REGION=us-east-1
'   IAM role: textract:DetectDocumentText, textract:AnalyzeDocument
'   IAM role: s3:PutObject, s3:DeleteObject (for any PDF processing)
'   S3 bucket: my-textract-staging-bucket (with lifecycle policy to prevent cost accumulation)

Public Class TextractOcrService
    Private ReadOnly _textractClient As AmazonTextractClient
    Private ReadOnly _s3Client As AmazonS3Client ' required for PDFs

    Public Sub New()
        ' Fails with AmazonClientException if credentials not found in chain
        _textractClient = New AmazonTextractClient(Amazon.RegionEndpoint.USEast1)
        _s3Client = New AmazonS3Client(Amazon.RegionEndpoint.USEast1)
    End Sub
End Class

// IronOCR: one line, one string, done
IronOcr.License.LicenseKey = "YOUR-LICENSE-KEY";

// Or from environment (no IAM, no rotation, no S3)
IronOcr.License.LicenseKey = Environment.GetEnvironmentVariable("IRONOCR_LICENSE");

Imports System

' IronOCR: one line, one string, done
IronOcr.License.LicenseKey = "YOUR-LICENSE-KEY"

' Or from environment (no IAM, no rotation, no S3)
IronOcr.License.LicenseKey = Environment.GetEnvironmentVariable("IRONOCR_LICENSE")

dotnet remove package AWSSDK.Textract
dotnet remove package AWSSDK.S3
dotnet remove package AWSSDK.Core

// Before (AWS Textract)
using Amazon.Textract;
using Amazon.Textract.Model;
using Amazon.S3;
using Amazon.S3.Model;
using Amazon.Runtime;

// After (IronOCR)
using IronOcr;

Imports Amazon.Textract
Imports Amazon.Textract.Model
Imports Amazon.S3
Imports Amazon.S3.Model
Imports Amazon.Runtime

Imports IronOcr

// Remove from startup:
//   AWS_ACCESS_KEY_ID environment variable
//   AWS_SECRET_ACCESS_KEY environment variable
//   AWS_DEFAULT_REGION environment variable
//   ~/.aws/credentials file entries
//   IAM role bindings on the execution context

// Add instead:
IronOcr.License.LicenseKey = "YOUR-LICENSE-KEY";

' Remove from startup:
'   AWS_ACCESS_KEY_ID environment variable
'   AWS_SECRET_ACCESS_KEY environment variable
'   AWS_DEFAULT_REGION environment variable
'   ~/.aws/credentials file entries
'   IAM role bindings on the execution context

' Add instead:
IronOcr.License.LicenseKey = "YOUR-LICENSE-KEY"

// Requires: NuGet AWSSDK.Textract, AWSSDK.S3
// Requires: AWS_ACCESS_KEY_ID, AWS_SECRET_ACCESS_KEY, AWS_DEFAULT_REGION in environment
// Requires: IAM policy with textract:* and s3:PutObject, s3:DeleteObject

using Amazon.S3;
using Amazon.Textract;

public class DocumentOcrService
{
    private readonly AmazonTextractClient _textractClient;
    private readonly AmazonS3Client _s3Client;
    private readonly string _stagingBucket;

    public DocumentOcrService(IConfiguration config)
    {
        // Credential chain: environment → ~/.aws/credentials → EC2 instance profile
        // Fails if none found — runtime exception, not compile-time
        _textractClient = new AmazonTextractClient(Amazon.RegionEndpoint.USEast1);
        _s3Client = new AmazonS3Client(Amazon.RegionEndpoint.USEast1);
        _stagingBucket = config["Textract:StagingBucket"]; // bucket must exist and have permissions
    }

    public async Task<string> ReadImageAsync(string imagePath)
    {
        var bytes = File.ReadAllBytes(imagePath);
        var response = await _textractClient.DetectDocumentTextAsync(
            new DetectDocumentTextRequest
            {
                Document = new Document { Bytes = new MemoryStream(bytes) }
            });

        return string.Join("\n", response.Blocks
            .Where(b => b.BlockType == BlockType.LINE)
            .Select(b => b.Text));
    }
}

Imports Amazon.S3
Imports Amazon.Textract
Imports System.IO
Imports System.Threading.Tasks
Imports Microsoft.Extensions.Configuration

Public Class DocumentOcrService
    Private ReadOnly _textractClient As AmazonTextractClient
    Private ReadOnly _s3Client As AmazonS3Client
    Private ReadOnly _stagingBucket As String

    Public Sub New(config As IConfiguration)
        ' Credential chain: environment → ~/.aws/credentials → EC2 instance profile
        ' Fails if none found — runtime exception, not compile-time
        _textractClient = New AmazonTextractClient(Amazon.RegionEndpoint.USEast1)
        _s3Client = New AmazonS3Client(Amazon.RegionEndpoint.USEast1)
        _stagingBucket = config("Textract:StagingBucket") ' bucket must exist and have permissions
    End Sub

    Public Async Function ReadImageAsync(imagePath As String) As Task(Of String)
        Dim bytes = File.ReadAllBytes(imagePath)
        Dim response = Await _textractClient.DetectDocumentTextAsync(
            New DetectDocumentTextRequest With {
                .Document = New Document With {.Bytes = New MemoryStream(bytes)}
            })

        Return String.Join(vbCrLf, response.Blocks _
            .Where(Function(b) b.BlockType = BlockType.LINE) _
            .Select(Function(b) b.Text))
    End Function
End Class

// Requires: NuGet IronOcr
// Requires: one license key string — nothing else

using IronOcr;

public class DocumentOcrService
{
    private readonly IronTesseract _ocr;

    public DocumentOcrService()
    {
        IronOcr.License.LicenseKey = "YOUR-LICENSE-KEY"; // or set at Program.cs startup
        _ocr = new IronTesseract();
    }

    public string ReadImage(string imagePath)
    {
        // No credential chain, no region, no bucket — just read
        return _ocr.Read(imagePath).Text;
    }
}

Imports IronOcr

Public Class DocumentOcrService
    Private ReadOnly _ocr As IronTesseract

    Public Sub New()
        IronOcr.License.LicenseKey = "YOUR-LICENSE-KEY" ' or set at Program.vb startup
        _ocr = New IronTesseract()
    End Sub

    Public Function ReadImage(imagePath As String) As String
        ' No credential chain, no region, no bucket — just read
        Return _ocr.Read(imagePath).Text
    End Function
End Class

// Textract cannot accept TIFF directly — requires PDF conversion + S3 + async job
// This shows the conversion overhead plus the minimum async pipeline

using Amazon.S3;
using Amazon.S3.Model;
using Amazon.Textract;
using Amazon.Textract.Model;

public async Task<string> ProcessScannedTiffAsync(string tiffPath, string s3Bucket)
{
    // Step 0: Convert TIFF to PDF first (Textract does not accept TIFF for async jobs)
    // Requires a separate PDF conversion library — not shown here
    var pdfPath = Path.ChangeExtension(tiffPath, ".pdf");
    ConvertTiffToPdf(tiffPath, pdfPath); // external dependency required

    // Step 1: Upload converted PDF to S3
    var s3Key = $"staging/{Guid.NewGuid()}.pdf";
    using (var stream = File.OpenRead(pdfPath))
    {
        await _s3Client.PutObjectAsync(new PutObjectRequest
        {
            BucketName = s3Bucket,
            Key = s3Key,
            InputStream = stream
        });
    }

    try
    {
        // Step 2: Start async detection job
        var startResp = await _textractClient.StartDocumentTextDetectionAsync(
            new StartDocumentTextDetectionRequest
            {
                DocumentLocation = new DocumentLocation
                {
                    S3Object = new S3Object { Bucket = s3Bucket, Name = s3Key }
                }
            });

        // Step 3: Poll every 5 seconds — can block for 30–120 seconds on large files
        GetDocumentTextDetectionResponse pollResp;
        do
        {
            await Task.Delay(5000);
            pollResp = await _textractClient.GetDocumentTextDetectionAsync(
                new GetDocumentTextDetectionRequest { JobId = startResp.JobId });
        } while (pollResp.JobStatus == JobStatus.IN_PROGRESS);

        if (pollResp.JobStatus != JobStatus.SUCCEEDED)
            throw new Exception($"Job failed: {pollResp.StatusMessage}");

        // Step 4: Collect paginated results
        var text = new StringBuilder();
        string token = null;
        do
        {
            var page = await _textractClient.GetDocumentTextDetectionAsync(
                new GetDocumentTextDetectionRequest
                {
                    JobId = startResp.JobId,
                    NextToken = token
                });
            foreach (var block in page.Blocks.Where(b => b.BlockType == BlockType.LINE))
                text.AppendLine(block.Text);
            token = page.NextToken;
        } while (token != null);

        return text.ToString();
    }
    finally
    {
        // Step 5: Clean up S3 — orphaned objects accumulate storage costs
        await _s3Client.DeleteObjectAsync(s3Bucket, s3Key);
        File.Delete(pdfPath); // clean up intermediate PDF
    }
}

Imports Amazon.S3
Imports Amazon.S3.Model
Imports Amazon.Textract
Imports Amazon.Textract.Model
Imports System.IO
Imports System.Text
Imports System.Threading.Tasks

Public Async Function ProcessScannedTiffAsync(tiffPath As String, s3Bucket As String) As Task(Of String)
    ' Step 0: Convert TIFF to PDF first (Textract does not accept TIFF for async jobs)
    ' Requires a separate PDF conversion library — not shown here
    Dim pdfPath = Path.ChangeExtension(tiffPath, ".pdf")
    ConvertTiffToPdf(tiffPath, pdfPath) ' external dependency required

    ' Step 1: Upload converted PDF to S3
    Dim s3Key = $"staging/{Guid.NewGuid()}.pdf"
    Using stream = File.OpenRead(pdfPath)
        Await _s3Client.PutObjectAsync(New PutObjectRequest With {
            .BucketName = s3Bucket,
            .Key = s3Key,
            .InputStream = stream
        })
    End Using

    Try
        ' Step 2: Start async detection job
        Dim startResp = Await _textractClient.StartDocumentTextDetectionAsync(
            New StartDocumentTextDetectionRequest With {
                .DocumentLocation = New DocumentLocation With {
                    .S3Object = New S3Object With {.Bucket = s3Bucket, .Name = s3Key}
                }
            })

        ' Step 3: Poll every 5 seconds — can block for 30–120 seconds on large files
        Dim pollResp As GetDocumentTextDetectionResponse
        Do
            Await Task.Delay(5000)
            pollResp = Await _textractClient.GetDocumentTextDetectionAsync(
                New GetDocumentTextDetectionRequest With {.JobId = startResp.JobId})
        Loop While pollResp.JobStatus = JobStatus.IN_PROGRESS

        If pollResp.JobStatus <> JobStatus.SUCCEEDED Then
            Throw New Exception($"Job failed: {pollResp.StatusMessage}")
        End If

        ' Step 4: Collect paginated results
        Dim text = New StringBuilder()
        Dim token As String = Nothing
        Do
            Dim page = Await _textractClient.GetDocumentTextDetectionAsync(
                New GetDocumentTextDetectionRequest With {
                    .JobId = startResp.JobId,
                    .NextToken = token
                })
            For Each block In page.Blocks.Where(Function(b) b.BlockType = BlockType.LINE)
                text.AppendLine(block.Text)
            Next
            token = page.NextToken
        Loop While token IsNot Nothing

        Return text.ToString()
    Finally
        ' Step 5: Clean up S3 — orphaned objects accumulate storage costs
        Await _s3Client.DeleteObjectAsync(s3Bucket, s3Key)
        File.Delete(pdfPath) ' clean up intermediate PDF
    End Try
End Function

//IronOCRreads multi-frame TIFF directly — no conversion, no S3, no polling

using IronOcr;

public string ProcessScannedTiff(string tiffPath)
{
    using var input = new OcrInput();
    input.LoadImageFrames(tiffPath); // reads all frames natively

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

    // Access per-page results if needed
    foreach (var page in result.Pages)
        Console.WriteLine($"Page {page.PageNumber}: {page.Words.Length} words detected");

    return result.Text;
}

Imports IronOcr

Public Function ProcessScannedTiff(tiffPath As String) As String
    Using input As New OcrInput()
        input.LoadImageFrames(tiffPath) ' reads all frames natively

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

        ' Access per-page results if needed
        For Each page In result.Pages
            Console.WriteLine($"Page {page.PageNumber}: {page.Words.Length} words detected")
        Next

        Return result.Text
    End Using
End Function

// Textract extracts text but cannot produce searchable PDFs
// Requires: S3 upload + async job + separate PDF library to embed the text layer

using Amazon.S3;
using Amazon.S3.Model;
using Amazon.Textract;
using Amazon.Textract.Model;

public async Task<string> ExtractTextForSearchableLayerAsync(
    string scannedPdfPath,
    string s3Bucket)
{
    // Must upload to S3 — cannot pass PDF bytes directly for async jobs
    var key = $"ocr-input/{Guid.NewGuid()}.pdf";

    await using (var fs = File.OpenRead(scannedPdfPath))
    {
        await _s3Client.PutObjectAsync(new PutObjectRequest
        {
            BucketName = s3Bucket,
            Key = key,
            InputStream = fs,
            ContentType = "application/pdf"
        });
    }

    string jobId;
    try
    {
        var startResp = await _textractClient.StartDocumentTextDetectionAsync(
            new StartDocumentTextDetectionRequest
            {
                DocumentLocation = new DocumentLocation
                {
                    S3Object = new S3Object { Bucket = s3Bucket, Name = key }
                }
            });
        jobId = startResp.JobId;
    }
    catch
    {
        await _s3Client.DeleteObjectAsync(s3Bucket, key);
        throw;
    }

    // Poll — minimum 5s wait; typical 15–60s for a 10-page PDF
    GetDocumentTextDetectionResponse pollResp;
    int pollAttempts = 0;
    const int maxAttempts = 120; // 10 minute timeout

    do
    {
        await Task.Delay(5000);
        pollResp = await _textractClient.GetDocumentTextDetectionAsync(
            new GetDocumentTextDetectionRequest { JobId = jobId });

        if (++pollAttempts >= maxAttempts)
            throw new TimeoutException("Textract job timed out after 10 minutes");

    } while (pollResp.JobStatus == JobStatus.IN_PROGRESS);

    await _s3Client.DeleteObjectAsync(s3Bucket, key); // cleanup regardless of outcome

    if (pollResp.JobStatus != JobStatus.SUCCEEDED)
        throw new Exception($"Textract job status: {pollResp.JobStatus} — {pollResp.StatusMessage}");

    // Return extracted text — caller must use a separate library to produce searchable PDF
    return string.Join("\n", pollResp.Blocks
        .Where(b => b.BlockType == BlockType.LINE)
        .Select(b => b.Text));

    // Caller still needs: iTextSharp, PdfSharp, or similar to embed text layer
}

Imports Amazon.S3
Imports Amazon.S3.Model
Imports Amazon.Textract
Imports Amazon.Textract.Model

Public Async Function ExtractTextForSearchableLayerAsync(
    scannedPdfPath As String,
    s3Bucket As String) As Task(Of String)

    ' Must upload to S3 — cannot pass PDF bytes directly for async jobs
    Dim key = $"ocr-input/{Guid.NewGuid()}.pdf"

    Await Using fs = File.OpenRead(scannedPdfPath)
        Await _s3Client.PutObjectAsync(New PutObjectRequest With {
            .BucketName = s3Bucket,
            .Key = key,
            .InputStream = fs,
            .ContentType = "application/pdf"
        })
    End Using

    Dim jobId As String
    Try
        Dim startResp = Await _textractClient.StartDocumentTextDetectionAsync(
            New StartDocumentTextDetectionRequest With {
                .DocumentLocation = New DocumentLocation With {
                    .S3Object = New S3Object With {.Bucket = s3Bucket, .Name = key}
                }
            })
        jobId = startResp.JobId
    Catch
        Await _s3Client.DeleteObjectAsync(s3Bucket, key)
        Throw
    End Try

    ' Poll — minimum 5s wait; typical 15–60s for a 10-page PDF
    Dim pollResp As GetDocumentTextDetectionResponse
    Dim pollAttempts As Integer = 0
    Const maxAttempts As Integer = 120 ' 10 minute timeout

    Do
        Await Task.Delay(5000)
        pollResp = Await _textractClient.GetDocumentTextDetectionAsync(
            New GetDocumentTextDetectionRequest With {.JobId = jobId})

        If System.Threading.Interlocked.Increment(pollAttempts) >= maxAttempts Then
            Throw New TimeoutException("Textract job timed out after 10 minutes")
        End If

    Loop While pollResp.JobStatus = JobStatus.IN_PROGRESS

    Await _s3Client.DeleteObjectAsync(s3Bucket, key) ' cleanup regardless of outcome

    If pollResp.JobStatus <> JobStatus.SUCCEEDED Then
        Throw New Exception($"Textract job status: {pollResp.JobStatus} — {pollResp.StatusMessage}")
    End If

    ' Return extracted text — caller must use a separate library to produce searchable PDF
    Return String.Join(vbLf, pollResp.Blocks _
        .Where(Function(b) b.BlockType = BlockType.LINE) _
        .Select(Function(b) b.Text))

    ' Caller still needs: iTextSharp, PdfSharp, or similar to embed text layer
End Function

//IronOCRreads the PDF and produces a searchable PDF output directly
// No S3, no polling, no external PDF library needed

using IronOcr;

public void ConvertToSearchablePdf(string scannedPdfPath, string outputPath)
{
    var ocr = new IronTesseract();

    using var input = new OcrInput();
    input.LoadPdf(scannedPdfPath);

    var result = ocr.Read(input);

    // Embed extracted text as searchable layer in one call
    result.SaveAsSearchablePdf(outputPath);

    Console.WriteLine($"Pages processed: {result.Pages.Length}");
    Console.WriteLine($"Overall confidence: {result.Confidence:F1}%");
}

Imports IronOcr

Public Sub ConvertToSearchablePdf(scannedPdfPath As String, outputPath As String)
    Dim ocr As New IronTesseract()

    Using input As New OcrInput()
        input.LoadPdf(scannedPdfPath)

        Dim result = ocr.Read(input)

        ' Embed extracted text as searchable layer in one call
        result.SaveAsSearchablePdf(outputPath)

        Console.WriteLine($"Pages processed: {result.Pages.Length}")
        Console.WriteLine($"Overall confidence: {result.Confidence:F1}%")
    End Using
End Sub

// AnalyzeDocument with TABLES returns blocks that must be graph-traversed
// to determine which words belong to which paragraphs

using Amazon.Textract;
using Amazon.Textract.Model;

public async Task<List<DocumentSection>> ExtractDocumentStructureAsync(string imagePath)
{
    var bytes = File.ReadAllBytes(imagePath);

    var response = await _textractClient.AnalyzeDocumentAsync(
        new AnalyzeDocumentRequest
        {
            Document = new Document { Bytes = new MemoryStream(bytes) },
            FeatureTypes = new List<string> { "TABLES", "FORMS" }
            // Note: AnalyzeDocument (TABLES) costs $0.015/page — 10x DetectDocumentText
        });

    var sections = new List<DocumentSection>();

    // Filter LINE blocks for paragraph reconstruction
    // LINE blocks are not grouped into paragraphs — must infer from Y proximity
    var lineBlocks = response.Blocks
        .Where(b => b.BlockType == BlockType.LINE)
        .OrderBy(b => b.Geometry?.BoundingBox?.Top ?? 0)
        .ToList();

    // Group lines into pseudo-paragraphs by vertical gap heuristic
    var currentParagraph = new List<Block>();
    float? lastBottom = null;
    const float paragraphGapThreshold = 0.02f; // 2% of page height

    foreach (var line in lineBlocks)
    {
        var top = line.Geometry?.BoundingBox?.Top ?? 0;
        var height = line.Geometry?.BoundingBox?.Height ?? 0;

        if (lastBottom.HasValue && (top - lastBottom.Value) > paragraphGapThreshold)
        {
            if (currentParagraph.Any())
            {
                sections.Add(new DocumentSection
                {
                    Text = string.Join(" ", currentParagraph.Select(b => b.Text)),
                    LineCount = currentParagraph.Count,
                    // Confidence: average of all LINE block confidence values
                    Confidence = (float)currentParagraph.Average(b => b.Confidence ?? 0)
                });
                currentParagraph.Clear();
            }
        }

        currentParagraph.Add(line);
        lastBottom = top + height;
    }

    if (currentParagraph.Any())
        sections.Add(new DocumentSection
        {
            Text = string.Join(" ", currentParagraph.Select(b => b.Text)),
            LineCount = currentParagraph.Count,
            Confidence = (float)currentParagraph.Average(b => b.Confidence ?? 0)
        });

    return sections;
}

public class DocumentSection
{
    public string Text { get; set; }
    public int LineCount { get; set; }
    public float Confidence { get; set; }
}

Imports Amazon.Textract
Imports Amazon.Textract.Model
Imports System.IO
Imports System.Linq
Imports System.Threading.Tasks

Public Class DocumentProcessor
    Private _textractClient As IAmazonTextract

    Public Sub New(textractClient As IAmazonTextract)
        _textractClient = textractClient
    End Sub

    Public Async Function ExtractDocumentStructureAsync(imagePath As String) As Task(Of List(Of DocumentSection))
        Dim bytes = File.ReadAllBytes(imagePath)

        Dim response = Await _textractClient.AnalyzeDocumentAsync(
            New AnalyzeDocumentRequest With {
                .Document = New Document With {.Bytes = New MemoryStream(bytes)},
                .FeatureTypes = New List(Of String) From {"TABLES", "FORMS"}
            })

        Dim sections = New List(Of DocumentSection)()

        Dim lineBlocks = response.Blocks _
            .Where(Function(b) b.BlockType = BlockType.LINE) _
            .OrderBy(Function(b) If(b.Geometry?.BoundingBox?.Top, 0)) _
            .ToList()

        Dim currentParagraph = New List(Of Block)()
        Dim lastBottom As Single? = Nothing
        Const paragraphGapThreshold As Single = 0.02F

        For Each line In lineBlocks
            Dim top = If(line.Geometry?.BoundingBox?.Top, 0)
            Dim height = If(line.Geometry?.BoundingBox?.Height, 0)

            If lastBottom.HasValue AndAlso (top - lastBottom.Value) > paragraphGapThreshold Then
                If currentParagraph.Any() Then
                    sections.Add(New DocumentSection With {
                        .Text = String.Join(" ", currentParagraph.Select(Function(b) b.Text)),
                        .LineCount = currentParagraph.Count,
                        .Confidence = CSng(currentParagraph.Average(Function(b) If(b.Confidence, 0)))
                    })
                    currentParagraph.Clear()
                End If
            End If

            currentParagraph.Add(line)
            lastBottom = top + height
        Next

        If currentParagraph.Any() Then
            sections.Add(New DocumentSection With {
                .Text = String.Join(" ", currentParagraph.Select(Function(b) b.Text)),
                .LineCount = currentParagraph.Count,
                .Confidence = CSng(currentParagraph.Average(Function(b) If(b.Confidence, 0)))
            })
        End If

        Return sections
    End Function
End Class

Public Class DocumentSection
    Public Property Text As String
    Public Property LineCount As Integer
    Public Property Confidence As Single
End Class

//IronOCRreturns a typed hierarchy — paragraphs are first-class objects
// No block graph, no heuristic gap detection, no confidence averaging

using IronOcr;

public List<DocumentSection> ExtractDocumentStructure(string imagePath)
{
    var ocr = new IronTesseract();
    var result = ocr.Read(imagePath);

    var sections = new List<DocumentSection>();

    foreach (var page in result.Pages)
    {
        foreach (var paragraph in page.Paragraphs)
        {
            sections.Add(new DocumentSection
            {
                Text = paragraph.Text,
                LineCount = paragraph.Lines.Length,
                // Coordinate access: exact pixel position on the page
                LocationX = paragraph.X,
                LocationY = paragraph.Y,
                Width = paragraph.Width,
                Height = paragraph.Height,
                Confidence = paragraph.Confidence
            });
        }
    }

    return sections;
}

public class DocumentSection
{
    public string Text { get; set; }
    public int LineCount { get; set; }
    public int LocationX { get; set; }
    public int LocationY { get; set; }
    public int Width { get; set; }
    public int Height { get; set; }
    public double Confidence { get; set; }
}

Imports IronOcr

Public Function ExtractDocumentStructure(imagePath As String) As List(Of DocumentSection)
    Dim ocr As New IronTesseract()
    Dim result = ocr.Read(imagePath)

    Dim sections As New List(Of DocumentSection)()

    For Each page In result.Pages
        For Each paragraph In page.Paragraphs
            sections.Add(New DocumentSection With {
                .Text = paragraph.Text,
                .LineCount = paragraph.Lines.Length,
                .LocationX = paragraph.X,
                .LocationY = paragraph.Y,
                .Width = paragraph.Width,
                .Height = paragraph.Height,
                .Confidence = paragraph.Confidence
            })
        Next
    Next

    Return sections
End Function

Public Class DocumentSection
    Public Property Text As String
    Public Property LineCount As Integer
    Public Property LocationX As Integer
    Public Property LocationY As Integer
    Public Property Width As Integer
    Public Property Height As Integer
    Public Property Confidence As Double
End Class

// Batch processing requires SemaphoreSlim throttle + retry on rate limit exceeded

using Amazon.Textract;
using Amazon.Textract.Model;
using System.Collections.Concurrent;

public async Task<Dictionary<string, string>> ProcessImageBatchAsync(
    IReadOnlyList<string> imagePaths,
    IProgress<(int Completed, int Total)> progress = null)
{
    var results = new ConcurrentDictionary<string, string>();
    var semaphore = new SemaphoreSlim(5); // 5 concurrent — Textract default TPS limit
    var tasks = new List<Task>();
    int completed = 0;

    foreach (var path in imagePaths)
    {
        await semaphore.WaitAsync();

        tasks.Add(Task.Run(async () =>
        {
            try
            {
                string text = null;
                int retryCount = 0;

                while (text == null && retryCount < 3)
                {
                    try
                    {
                        var bytes = await File.ReadAllBytesAsync(path);
                        var response = await _textractClient.DetectDocumentTextAsync(
                            new DetectDocumentTextRequest
                            {
                                Document = new Document { Bytes = new MemoryStream(bytes) }
                            });

                        text = string.Join("\n", response.Blocks
                            .Where(b => b.BlockType == BlockType.LINE)
                            .Select(b => b.Text));
                    }
                    catch (AmazonTextractException ex)
                        when (ex.ErrorCode == "ProvisionedThroughputExceededException")
                    {
                        // Exponential backoff on rate limit — blocks the entire thread
                        await Task.Delay(TimeSpan.FromSeconds(Math.Pow(2, retryCount)));
                        retryCount++;
                    }
                }

                results[path] = text ?? string.Empty;
                var done = Interlocked.Increment(ref completed);
                progress?.Report((done, imagePaths.Count));
            }
            finally
            {
                semaphore.Release();
            }
        }));
    }

    await Task.WhenAll(tasks);
    return results.ToDictionary(x => x.Key, x => x.Value);
}

Imports Amazon.Textract
Imports Amazon.Textract.Model
Imports System.Collections.Concurrent
Imports System.IO
Imports System.Threading

Public Async Function ProcessImageBatchAsync(
    imagePaths As IReadOnlyList(Of String),
    Optional progress As IProgress(Of (Completed As Integer, Total As Integer)) = Nothing) As Task(Of Dictionary(Of String, String))

    Dim results As New ConcurrentDictionary(Of String, String)()
    Dim semaphore As New SemaphoreSlim(5) ' 5 concurrent — Textract default TPS limit
    Dim tasks As New List(Of Task)()
    Dim completed As Integer = 0

    For Each path In imagePaths
        Await semaphore.WaitAsync()

        tasks.Add(Task.Run(Async Function()
            Try
                Dim text As String = Nothing
                Dim retryCount As Integer = 0

                While text Is Nothing AndAlso retryCount < 3
                    Try
                        Dim bytes = Await File.ReadAllBytesAsync(path)
                        Dim response = Await _textractClient.DetectDocumentTextAsync(
                            New DetectDocumentTextRequest With {
                                .Document = New Document With {.Bytes = New MemoryStream(bytes)}
                            })

                        text = String.Join(vbLf, response.Blocks _
                            .Where(Function(b) b.BlockType = BlockType.LINE) _
                            .Select(Function(b) b.Text))
                    Catch ex As AmazonTextractException When ex.ErrorCode = "ProvisionedThroughputExceededException"
                        ' Exponential backoff on rate limit — blocks the entire thread
                        Await Task.Delay(TimeSpan.FromSeconds(Math.Pow(2, retryCount)))
                        retryCount += 1
                    End Try
                End While

                results(path) = If(text, String.Empty)
                Dim done = Interlocked.Increment(completed)
                If progress IsNot Nothing Then
                    progress.Report((done, imagePaths.Count))
                End If
            Finally
                semaphore.Release()
            End Try
        End Function))
    Next

    Await Task.WhenAll(tasks)
    Return results.ToDictionary(Function(x) x.Key, Function(x) x.Value)
End Function

// No rate limits, no semaphore, no retry logic — Parallel.ForEach saturates all cores

using IronOcr;
using System.Collections.Concurrent;

public Dictionary<string, string> ProcessImageBatch(
    IReadOnlyList<string> imagePaths,
    IProgress<(int Completed, int Total)> progress = null)
{
    var ocr = new IronTesseract();
    var results = new ConcurrentDictionary<string, string>();
    int completed = 0;

    Parallel.ForEach(imagePaths, path =>
    {
        var result = ocr.Read(path);
        results[path] = result.Text;

        var done = Interlocked.Increment(ref completed);
        progress?.Report((done, imagePaths.Count));
    });

    return results.ToDictionary(x => x.Key, x => x.Value);
}

Imports IronOcr
Imports System.Collections.Concurrent
Imports System.Threading

Public Function ProcessImageBatch(
    imagePaths As IReadOnlyList(Of String),
    Optional progress As IProgress(Of (Completed As Integer, Total As Integer)) = Nothing) As Dictionary(Of String, String)

    Dim ocr As New IronTesseract()
    Dim results As New ConcurrentDictionary(Of String, String)()
    Dim completed As Integer = 0

    Parallel.ForEach(imagePaths, Sub(path)
                                     Dim result = ocr.Read(path)
                                     results(path) = result.Text

                                     Dim done = Interlocked.Increment(completed)
                                     If progress IsNot Nothing Then
                                         progress.Report((done, imagePaths.Count))
                                     End If
                                 End Sub)

    Return results.ToDictionary(Function(x) x.Key, Function(x) x.Value)
End Function

// FORMS mode costs $0.05/page — the most expensive Textract tier
// Relationship graph traversal required to reconstruct key-value pairs

using Amazon.Textract;
using Amazon.Textract.Model;

public async Task<Dictionary<string, string>> ExtractInvoiceFieldsAsync(string imagePath)
{
    var bytes = File.ReadAllBytes(imagePath);

    // $0.05/page for FORMS analysis
    var response = await _textractClient.AnalyzeDocumentAsync(
        new AnalyzeDocumentRequest
        {
            Document = new Document { Bytes = new MemoryStream(bytes) },
            FeatureTypes = new List<string> { "FORMS" }
        });

    var allBlocks = response.Blocks;
    var fields = new Dictionary<string, string>();

    // Find KEY blocks only
    var keyBlocks = allBlocks.Where(b =>
        b.BlockType == BlockType.KEY_VALUE_SET &&
        b.EntityTypes?.Contains("KEY") == true);

    foreach (var keyBlock in keyBlocks)
    {
        // Assemble key text from CHILD WORD blocks
        var keyText = GetTextFromBlock(allBlocks, keyBlock);

        // Find associated VALUE block via VALUE relationship
        var valueBlockId = keyBlock.Relationships?
            .FirstOrDefault(r => r.Type == RelationshipType.VALUE)?
            .Ids.FirstOrDefault();

        if (valueBlockId == null) continue;

        var valueBlock = allBlocks.FirstOrDefault(b => b.Id == valueBlockId);
        if (valueBlock == null) continue;

        var valueText = GetTextFromBlock(allBlocks, valueBlock);
        fields[keyText.TrimEnd(':')] = valueText;
    }

    return fields;
}

private string GetTextFromBlock(IList<Block> allBlocks, Block block)
{
    if (block.Relationships == null) return string.Empty;

    var childWordIds = block.Relationships
        .Where(r => r.Type == RelationshipType.CHILD)
        .SelectMany(r => r.Ids);

    return string.Join(" ", allBlocks
        .Where(b => b.BlockType == BlockType.WORD && childWordIds.Contains(b.Id))
        .Select(b => b.Text));
}

Imports Amazon.Textract
Imports Amazon.Textract.Model
Imports System.IO
Imports System.Threading.Tasks

Public Class InvoiceFieldExtractor
    Private _textractClient As AmazonTextractClient

    Public Async Function ExtractInvoiceFieldsAsync(imagePath As String) As Task(Of Dictionary(Of String, String))
        Dim bytes = File.ReadAllBytes(imagePath)

        ' $0.05/page for FORMS analysis
        Dim response = Await _textractClient.AnalyzeDocumentAsync(
            New AnalyzeDocumentRequest With {
                .Document = New Document With {.Bytes = New MemoryStream(bytes)},
                .FeatureTypes = New List(Of String) From {"FORMS"}
            })

        Dim allBlocks = response.Blocks
        Dim fields As New Dictionary(Of String, String)()

        ' Find KEY blocks only
        Dim keyBlocks = allBlocks.Where(Function(b) 
                                            Return b.BlockType = BlockType.KEY_VALUE_SET AndAlso
                                                   b.EntityTypes?.Contains("KEY") = True
                                        End Function)

        For Each keyBlock In keyBlocks
            ' Assemble key text from CHILD WORD blocks
            Dim keyText = GetTextFromBlock(allBlocks, keyBlock)

            ' Find associated VALUE block via VALUE relationship
            Dim valueBlockId = keyBlock.Relationships?.
                FirstOrDefault(Function(r) r.Type = RelationshipType.VALUE)?.
                Ids.FirstOrDefault()

            If valueBlockId Is Nothing Then Continue For

            Dim valueBlock = allBlocks.FirstOrDefault(Function(b) b.Id = valueBlockId)
            If valueBlock Is Nothing Then Continue For

            Dim valueText = GetTextFromBlock(allBlocks, valueBlock)
            fields(keyText.TrimEnd(":"c)) = valueText
        Next

        Return fields
    End Function

    Private Function GetTextFromBlock(allBlocks As IList(Of Block), block As Block) As String
        If block.Relationships Is Nothing Then Return String.Empty

        Dim childWordIds = block.Relationships.
            Where(Function(r) r.Type = RelationshipType.CHILD).
            SelectMany(Function(r) r.Ids)

        Return String.Join(" ", allBlocks.
            Where(Function(b) b.BlockType = BlockType.WORD AndAlso childWordIds.Contains(b.Id)).
            Select(Function(b) b.Text))
    End Function
End Class

// CropRectangle extracts each field zone directly — no relationship graph
// Works for any fixed-format form where field positions are known

using IronOcr;

// Define the field zones for your form template once
private static readonly Dictionary<string, CropRectangle> InvoiceFieldZones =
    new Dictionary<string, CropRectangle>
    {
        { "InvoiceNumber", new CropRectangle(450, 80,  300, 35) },
        { "InvoiceDate",   new CropRectangle(450, 120, 300, 35) },
        { "VendorName",    new CropRectangle(50,  160, 400, 35) },
        { "TotalAmount",   new CropRectangle(450, 680, 200, 35) },
        { "DueDate",       new CropRectangle(450, 720, 200, 35) }
    };

public Dictionary<string, string> ExtractInvoiceFields(string imagePath)
{
    var ocr = new IronTesseract();
    var fields = new Dictionary<string, string>();

    foreach (var zone in InvoiceFieldZones)
    {
        using var input = new OcrInput();
        input.LoadImage(imagePath, zone.Value); // load only the defined region

        var result = ocr.Read(input);
        fields[zone.Key] = result.Text.Trim();
    }

    return fields;
}

Imports IronOcr

' CropRectangle extracts each field zone directly — no relationship graph
' Works for any fixed-format form where field positions are known

' Define the field zones for your form template once
Private Shared ReadOnly InvoiceFieldZones As New Dictionary(Of String, CropRectangle) From {
    {"InvoiceNumber", New CropRectangle(450, 80, 300, 35)},
    {"InvoiceDate", New CropRectangle(450, 120, 300, 35)},
    {"VendorName", New CropRectangle(50, 160, 400, 35)},
    {"TotalAmount", New CropRectangle(450, 680, 200, 35)},
    {"DueDate", New CropRectangle(450, 720, 200, 35)}
}

Public Function ExtractInvoiceFields(imagePath As String) As Dictionary(Of String, String)
    Dim ocr As New IronTesseract()
    Dim fields As New Dictionary(Of String, String)()

    For Each zone In InvoiceFieldZones
        Using input As New OcrInput()
            input.LoadImage(imagePath, zone.Value) ' load only the defined region

            Dim result = ocr.Read(input)
            fields(zone.Key) = result.Text.Trim()
        End Using
    Next

    Return fields
End Function

// Single environment variable — no IAM, no rotation, no chain resolution
var key = Environment.GetEnvironmentVariable("IRONOCR_LICENSE");
if (string.IsNullOrEmpty(key))
    throw new InvalidOperationException("IRONOCR_LICENSE environment variable is not set");

IronOcr.License.LicenseKey = key;

Imports System

' Single environment variable — no IAM, no rotation, no chain resolution
Dim key As String = Environment.GetEnvironmentVariable("IRONOCR_LICENSE")
If String.IsNullOrEmpty(key) Then
    Throw New InvalidOperationException("IRONOCR_LICENSE environment variable is not set")
End If

IronOcr.License.LicenseKey = key

// If the call site must remain async (e.g., an ASP.NET controller action):
public async Task<IActionResult> ProcessUpload(IFormFile file)
{
    using var ms = new MemoryStream();
    await file.CopyToAsync(ms);

    // Offload synchronous OCR to thread pool — keeps controller non-blocking
    var text = await Task.Run(() =>
    {
        var ocr = new IronTesseract();
        using var input = new OcrInput();
        input.LoadImage(ms.ToArray());
        return ocr.Read(input).Text;
    });

    return Ok(text);
}

Imports System.IO
Imports System.Threading.Tasks
Imports Microsoft.AspNetCore.Mvc

Public Class YourController
    Inherits Controller

    ' If the call site must remain async (e.g., an ASP.NET controller action):
    Public Async Function ProcessUpload(file As IFormFile) As Task(Of IActionResult)
        Using ms As New MemoryStream()
            Await file.CopyToAsync(ms)

            ' Offload synchronous OCR to thread pool — keeps controller non-blocking
            Dim text = Await Task.Run(Function()
                                          Dim ocr = New IronTesseract()
                                          Using input As New OcrInput()
                                              input.LoadImage(ms.ToArray())
                                              Return ocr.Read(input).Text
                                          End Using
                                      End Function)

            Return Ok(text)
        End Using
    End Function
End Class

// Before: upload → job → poll → extract → cleanup (50+ lines)
// After: two lines, no cleanup required

using var input = new OcrInput();
input.LoadPdf(localPdfPath);
var text = new IronTesseract().Read(input).Text;

Imports IronOcr

Using input As New OcrInput()
    input.LoadPdf(localPdfPath)
    Dim text As String = New IronTesseract().Read(input).Text
End Using

// Before: filter by BlockType + traverse relationship IDs
var paragraphText = string.Join(" ", allBlocks
    .Where(b => b.BlockType == BlockType.WORD &&
                childIds.Contains(b.Id))
    .Select(b => b.Text));

// After: direct paragraph text (no filtering, no relationship lookup)
foreach (var page in result.Pages)
    foreach (var para in page.Paragraphs)
        Console.WriteLine(para.Text); // already assembled

' Before: filter by BlockType + traverse relationship IDs
Dim paragraphText As String = String.Join(" ", allBlocks _
    .Where(Function(b) b.BlockType = BlockType.WORD AndAlso _
                childIds.Contains(b.Id)) _
    .Select(Function(b) b.Text))

' After: direct paragraph text (no filtering, no relationship lookup)
For Each page In result.Pages
    For Each para In page.Paragraphs
        Console.WriteLine(para.Text) ' already assembled
    Next
Next

// Delete: SemaphoreSlim, retry loops, ProvisionedThroughputExceededException handlers
// Replace with:
Parallel.ForEach(imagePaths, path =>
{
    var result = new IronTesseract().Read(path);
    results[path] = result.Text;
});

Imports System.Threading.Tasks

Parallel.ForEach(imagePaths, Sub(path)
    Dim result = New IronTesseract().Read(path)
    results(path) = result.Text
End Sub)

grep -rn "Amazon.Textract\|AmazonTextractClient\|DetectDocumentText" --include="*.cs" .
grep -rn "StartDocumentTextDetection\|GetDocumentTextDetection\|JobStatus" --include="*.cs" .
grep -rn "AmazonS3Client\|PutObjectRequest\|DeleteObjectAsync" --include="*.cs" .
grep -rn "BlockType\|RelationshipType\|KEY_VALUE_SET" --include="*.cs" .
grep -rn "ProvisionedThroughputExceededException\|AmazonTextractException" --include="*.cs" .
grep -rn "AWSSDK\|Amazon.RegionEndpoint" --include="*.csproj" .