OfficeIMO.Reader.Ocr.Tesseract 3.0.0

OfficeIMO.Reader.Ocr.Tesseract - Tesseract OCR provider

OfficeIMO.Reader.Ocr.Tesseract is an optional IOfficeOcrEngine backed by an installed Tesseract command-line executable. It does not bundle native binaries or trained language data.

Install

dotnet add package OfficeIMO.Reader.Ocr.Tesseract
dotnet add package OfficeIMO.Reader.Pdf

Install Tesseract separately for the host operating system, then verify the executable and required languages:

tesseract --version
tesseract --list-langs

Tesseract 5 is the current stable major line. Its command contract supports image input, language expressions, and TSV output; see the official Tesseract manual.

Recognize Reader candidates

using OfficeIMO.Reader;
using OfficeIMO.Reader.Ocr.Tesseract;
using OfficeIMO.Reader.Pdf;

OfficeDocumentReader reader = new OfficeDocumentReaderBuilder()
    .AddPdfHandler()
    .Build();
OfficeDocumentReadResult source = reader.ReadDocument("scanned.pdf");
var engine = new TesseractOcrEngine(new TesseractOcrEngineOptions {
    ExecutablePath = "tesseract",
    Language = "eng+pol",
    PageSegmentationMode = 3,
    Timeout = TimeSpan.FromMinutes(1)
});

OfficeDocumentOcrExecutionResult execution = await source.ApplyOcrAsync(
    engine,
    new OfficeDocumentOcrExecutionOptions {
        MaxCandidates = 25,
        MaxDegreeOfParallelism = 2,
        MaxTotalInputBytes = 64L * 1024L * 1024L
    });

foreach (OfficeDocumentOcrRecognition recognition in execution.Recognitions) {
    foreach (OfficeOcrTextSpan span in recognition.Result.Spans) {
        Console.WriteLine($"{span.Level}: {span.Text} ({span.Confidence:P0})");
    }
}

The provider parses Tesseract TSV into line and word spans with pixel bounding boxes and normalized confidence. Tesseract TSV does not expose character boxes, so SupportsCharacterSpans is false. A process or delegate engine can still return character spans through the shared core contract.

GetVersionAsync() and GetLanguagesAsync() provide explicit installation discovery. Missing executables, trained data, unsupported input formats, and nonzero process exits surface as engine failures; ApplyOcrAsync converts them to structured diagnostics when ContinueOnError is enabled.

Per-request payload and output files use owner-only Unix directories and permissions. Temporary files are deleted by default; enable KeepTemporaryFiles only for controlled diagnostics.

Targets and licenses

• Targets: netstandard2.0, net8.0, net10.0 (net472 is also included on Windows builds).
• OfficeIMO provider license: MIT.
• Tesseract is an external dependency distributed under its own Apache 2.0 license.

Dependency footprint

• External: An installed Tesseract CLI and its language data; neither is bundled.
• OfficeIMO: OfficeIMO.Reader.Core and OfficeIMO.Reader.Ocr.Process own the OCR contract, bounded process execution, TSV projection, and diagnostics.

See the complete OfficeIMO package map for related formats and conversion paths.