InPoint.Cloud.OpenBarcode 0.1.0

OpenBarcode

An open-source barcode reader for .NET that reads images and PDF files with managed code only: no native libraries, no System.Drawing, no Ghostscript or PDFium. It runs anywhere .NET runs (Windows, Linux, macOS, containers, Azure Functions) and targets .NET Standard 2.0 and .NET 8.

using InPoint.Cloud.OpenBarcode;

var reader = new BarcodeReader();
foreach (var barcode in reader.ReadFile("invoice.pdf"))
    Console.WriteLine($"page {barcode.PageNumber}: {barcode.Format} {barcode.Text}");

Install

dotnet add package InPoint.Cloud.OpenBarcode
dotnet tool install -g InPoint.Cloud.OpenBarcode.Cli   # command: openbarcode

The namespace is InPoint.Cloud.OpenBarcode.

What it reads

Symbologies: QR Code, Data Matrix, PDF417, Aztec, Code 128 (incl. GS1-128), Code 39, Code 93, Codabar, EAN-13, EAN-8, UPC-A, UPC-E, ITF, GS1 DataBar (+ Expanded), MaxiCode (clean crops only) and MSI (opt-in).

Images: PNG, JPEG, BMP, GIF, TIFF (all pages, incl. CCITT G3/G4 fax compression), TGA, PSD, PBM/PGM/PPM. Transparent images are composited on white, so black-on-transparent barcode PNGs work.

PDFs: two kinds of content are searched on every page:

• Embedded images such as scans: JPEG (DCT), Flate, LZW, CCITT G3/G4 and JBIG2 (generic and symbol-coded), in gray, RGB, CMYK and indexed colour, image masks and /Decode inversions.
• Vector graphics: barcodes that PDF generators draw as filled rectangles, paths or stroked lines (reportlab, iText, Crystal Reports, label printers' "print to PDF", ...). The reader rasterizes the page's paths at 300 dpi with its own scanline renderer and decodes the result.

The same code found twice on one page (for example as both an image and vector art) is reported once.

Usage

var reader = new BarcodeReader(new BarcodeReaderOptions
{
    Formats = BarcodeFormat.QrCode | BarcodeFormat.Code128,  // fewer formats = faster, fewer false positives
    PdfFirstPage = 1,
    PdfLastPage = 3,
});

// From a path, a Stream or a byte[]; the type is detected from the content, not the extension.
IReadOnlyList<BarcodeResult> results = reader.ReadFile("scan.tif");

// PDFs: find out which images had to be skipped.
var warnings = new List<string>();
results = reader.Read(File.ReadAllBytes("doc.pdf"), warnings);

// Pixels you already have (System.Drawing, SkiaSharp, ImageSharp, a camera frame, ...).
var image = GrayImage.FromPixels(bgraBytes, width, height, PixelLayout.Bgra32, stride);
results = reader.Read(image);

Each BarcodeResult has Text, Format, RawBytes, Points (corner or end points, in pixels of the image it was decoded from), Source (Image, PdfImage, PdfVector), PageNumber (PDFs, 1-based) and FrameIndex (TIFF page, or image index on a PDF page).

BarcodeReader is immutable and thread-safe; share one instance.

Options

Command line

dotnet run --project src/OpenBarcode.Cli -- invoice.pdf scans/*.tif
dotnet run --project src/OpenBarcode.Cli -- --json --formats qr,datamatrix label.png

Run with --help for all options. Output is file[:page]<TAB>format<TAB>text; the exit code is 0 when something was found, 1 when nothing was, 2 on errors.

Performance

A full A4 page scanned at 300 dpi takes roughly 0.5–2 s with the thorough defaults on one core. Restricting Formats, setting ReadMultiple = false (stop at the first code) or TryHarder = false makes it several times faster. Pages are independent, so batches parallelise well.

Limitations

• Barcodes set as text in a barcode font inside a PDF are not detected (glyphs are not rendered). Most generators draw bars as paths or images, which work.
• JPEG 2000 (JPXDecode) images in PDFs are skipped with a warning; no managed decoder is used.
• The vector renderer ignores clipping paths, soft masks and shading patterns.
• Damaged, very blurry or strongly perspective-distorted photos may not decode; this is a document reader first, not a camera scanner.

How it works

file ──► sniff type ─┬─► image decoders (StbImageSharp, LibTiff.NET, built-in PNM) ──────────────┐
                     └─► PdfPig ─┬─► embedded images ─► filters (+ managed JBIG2) ─► grayscale ─┤
                                 └─► paths ─► scanline rasterizer (this project) ───────────────┤
                                                                                                 ▼
                         ZXing.Net detectors ◄── quiet-zone padding, upscaling of tiny images,
                                                 90° pass for 1D, blob crops for Data Matrix/Aztec,
                                                 fragment and duplicate filtering

ZXing's Data Matrix and Aztec detectors search outward from the image centre, so on a page with several codes they only see one. The reader proposes compact ink blobs and gives each its own crop. Partial reads that ZXing can report inside a longer 1D barcode (a "UPC-E" made of half an EAN-13) are filtered out.

Building and testing

Needs the .NET 10 SDK (for the .slnx solution file); the library itself targets .NET Standard 2.0 and .NET 8.

dotnet build
dotnet test

The tests generate barcodes in every supported symbology and file format, build PDFs with hand-written content streams and image dictionaries, and read real-world-style samples made by reportlab, poppler, ImageMagick and jbig2enc (tests/samples).

License

Apache-2.0. See THIRD-PARTY-NOTICES.md for the libraries it builds on.

Releasing

Push a tag such as v0.1.0 (or v0.2.0-beta.1 for a prerelease). The Release workflow builds, tests, packs and publishes both packages to nuget.org under the InPoint.Cloud account using Trusted Publishing, then creates a GitHub release with the packages attached. The package version comes from the tag.