SharpAstro.Jpeg.GainMap 3.7.651

SharpAstro Codecs

A family of pure-managed, AOT-compatible image-codec packages for .NET 10 — no native binaries. Each format ships as an independent NuGet, and SharpAstro.Codecs is a thin facade that sniffs a byte stream by its magic bytes and dispatches to the right decoder, so a consumer can reference one package instead of cherry-picking codecs.

See CODECS.md for the full per-package matrix, what each codec does and does not support, and how to pick the right one. A bundled sRGB ICC profile ships in SharpAstro.Color.Icc for embedding.

All packages target net10.0, are IsAotCompatible, ship SourceLink debugging, and publish in lockstep (shared Major.Minor + CI run-number patch).

NuGet

# One facade for sniff-and-decode (PNG, JPEG incl. Ultra HDR, TIFF, JXR, EXR, JXL, .jb2):
dotnet add package SharpAstro.Codecs

# ...or reference just the format(s) you need:
dotnet add package SharpAstro.Png
dotnet add package SharpAstro.Jxr

Usage

Decode any supported still image through the facade — sniff the header, size a buffer, decode into it:

using SharpAstro.Codecs;

var bytes = File.ReadAllBytes(path);
if (ImageCodecs.TryReadInfo(bytes, out var info))
{
    var rgba = new byte[info.Width * info.Height * 4];
    ImageCodecs.TryDecodeIntoRgba8(bytes, rgba);      // zero-copy into your buffer
    // ...or ImageCodecs.TryDecode(bytes, out IDecodedImage img) for the full-fidelity raster.
}

Each codec is also usable directly — e.g. PngReader / PngWriter, JpegDecoder.Decode / DecodeTo, TiffReader / TiffWriter, JxrImageCodec, ExrImageCodec, JxlImageCodec. See CODECS.md.

JBIG2 is the one format whose main entry point is not the facade. A PDF-embedded JBIG2 stream has no file header to sniff, keeps its shared segment dictionaries in a separate /JBIG2Globals stream, and takes its dimensions from the image dictionary — so those callers pass all three explicitly:

using SharpAstro.Jbig2;

// `embedded` / `globals` are the PDF streams; width/height come from the image dictionary.
var page = Jbig2Decoder.Decode(embedded, globals, width, height);
var bits = page.Bits;        // one byte per pixel, 1 = black (T.88 polarity)
var gray = page.ToGray8();   // ...or the 8-bit projection, black 0 / white 255

Standalone .jb2 files do have a signature, and decode through the facade like anything else — generic, symbol-coded and halftone pages alike.

JBIG2 covers every region type T.88 defines on the arithmetic path: generic regions (both the template coder and MMR / ITU-T T.6, the Group 4 fax coding), refinement regions, symbol dictionaries and text regions, and pattern dictionaries with halftone regions. The Huffman-coded variants (SDHUFF / SBHUFF) are refused rather than guessed at — no available encoder emits them, so an implementation would have nothing to validate itself against.

Building from source

git clone https://github.com/SharpAstro/Codecs
cd Codecs
dotnet build Codecs.JustTests.sln -c Release
dotnet test  Codecs.JustTests.sln -c Release

Requires the .NET 10 SDK.

License

Unlicense (public domain).

Credits

This repository began as a fork of StbSharp/StbImageSharp (Roman Shapiro's C# port of Sean Barrett's stb_image.h, via the Hebron C-to-C# transpiler). SharpAstro.Jpeg's decoder was ported from and validated byte-exact against that reference decoder before the stb port itself was retired from the repo.