Lyo.Pdf.Ocr 1.0.2

Lyo.Pdf.Ocr

Glues Lyo.Pdf.Rendering (PDFium → PNG) to an IOcrEngine from Lyo.Images.Ocr and projects OCR pixel boxes back into PDF coordinate space.

Targets net10.0.

Examples

Register with DI

services.AddTesseractOcrEngineFromConfiguration(configuration); // or any IOcrEngine
services.AddPdfOcr();

Example

public sealed class Worker(PdfOcrService pdfOcr, IPdfService pdfService)
{
    public async Task<PdfOcrDocumentPage> RunAsync(byte[] pdfBytes, CancellationToken ct)
    {
        await using var reader = await pdfService.OpenFromBytesAsync(pdfBytes, ct);
        var result = await pdfOcr.ReadPageAsync(reader, pageNumber1Based: 1, dpi: 200, cancellationToken: ct);
        return result.ValueOrThrow();
    }
}

API

PdfOcrService exposes a single method:

Task<Result<PdfOcrDocumentPage>> ReadPageAsync(
    IPdfReader pdfReader,
    int pageNumber1Based,
    int dpi,
    OcrReadRequest? ocrRequest = null,
    string? pdfPassword = null,
    CancellationToken cancellationToken = default);

The pipeline:

1. pdfReader.GetPageSizePoints(pageNumber1Based) for the PDF page dimensions.
2. IPdfPageRasterizer.RenderPageToPngAsync(pdfReader.SourceBytes, …) for the pixel raster (and bitmap width/height).
3. IOcrEngine.ReadAsync(pngStream, ocrRequest, …) for the per-word text and pixel-space bounding boxes (Y-up).
4. OcrCoordinateTransforms.MapPixelBoxToPdfPoints(box, pageWidthPts, pageHeightPts, widthPx, heightPx) to lift each OcrWord into a PdfWord.

PdfOcrDocumentPage carries the original OcrPageResult plus the projected IReadOnlyList<PdfWord> WordsInPdfPoints and the source page size.

Failures from either stage propagate as Result<PdfOcrDocumentPage>.Failure; unexpected exceptions are tagged with PdfOcrErrorCodes.ReadFailed ("PDF_OCR_READ_FAILED").

Dependency injection

AddPdfOcr registers PdfOcrService as a singleton and calls AddPdfPageRasterizer if IPdfPageRasterizer is not already registered. IOcrEngine must be registered separately.

Example

For selectable-text PDFs prefer IPdfReader.Text (PdfPig) directly — OCR only helps when the PDF lacks an embedded text layer.

Dependencies

Generated from ProjectReference / PackageReference (same model as docs/Lyo.ProjectGraph.html).

• Lyo.Exceptions — (direct, lyo)
• Lyo.Images.Ocr — (direct, lyo)
• Lyo.Pdf.Models — (direct, lyo)
• Lyo.Pdf.Rendering — (direct, lyo)
• Microsoft.Extensions.DependencyInjection.Abstractions 10.0.5 — (direct, microsoft)
• Microsoft.Extensions.Logging.Abstractions 10.0.5 — (direct, microsoft)
• Lyo.Common — (transitive, lyo)
• Lyo.DataTable.Models — (transitive, lyo)
• Lyo.Metrics — (transitive, lyo)
• Lyo.Result — (transitive, lyo)
• Microsoft.Extensions.Configuration.Binder 10.0.5 — (transitive, microsoft)
• Microsoft.Extensions.Options.ConfigurationExtensions 10.0.5 — (transitive, microsoft)
• PDFtoImage 5.2.1 — (transitive, third-party)
• SixLabors.ImageSharp 3.1.12 — (transitive, third-party)
• System.Memory 4.6.3 — (transitive, microsoft, netstandard2.0)
• System.Text.Json 10.0.5 — (transitive, microsoft, netstandard2.0)