DotImage 0.1.0

DotImage

A C# port of Go's standard library image package for .NET 8 and .NET 10.

DotImage provides 2D image types, color models, Porter–Duff compositing, and PNG, GIF, and JPEG codecs. The implementation follows Go's logic closely while exposing an idiomatic C# API (IImage, Memory<byte>, exceptions).

Features

• Core image types — RgbaImage, NrgbaImage, GrayImage, CmykImage, PalettedImage, YCbCrImage, and more
• Color — IColor, color models, RGB↔YCbCr, RGB↔CMYK, Plan9 and WebSafe palettes
• Drawing — DrawOps.Draw, DrawMask, Clip, Floyd–Steinberg dithering
• Codecs — PNG (all color types, interlaced, 16-bit), GIF (animation), JPEG (baseline + progressive decode)
• Auto-detect decode — FormatRegistry.Decode sniffs magic bytes and dispatches to the registered codec

Requirements

• .NET 8 SDK or .NET 10 SDK

Build & Test

dotnet build
dotnet test

Tests run on both net8.0 and net10.0 (209 tests).

Quick Start

Decode any supported format

PNG, GIF, and JPEG formats register automatically on the first call to FormatRegistry.Decode or DecodeConfig.

using DotImage;

using var stream = File.OpenRead("photo.png");
var (image, format) = FormatRegistry.Decode(stream);

Console.WriteLine($"{format}: {image.Bounds().Dx()}×{image.Bounds().Dy()}");

var (r, g, b, a) = image.At(0, 0).Rgba();

Decode config only (check dimensions before allocating)

using var stream = File.OpenRead("photo.jpg");
var (config, format) = FormatRegistry.DecodeConfig(stream);

Console.WriteLine($"{format}: {config.Width}×{config.Height}");

Create and draw on an image

using DotImage;
using DotImage.Color;
using DotImage.Draw;

var rect = Geometry.Rect(0, 0, 256, 256);
var dst = Images.NewRgba(rect);

DrawOps.Draw(dst, rect, UniformImages.White, Point.Origin, Op.Src);
DrawOps.Draw(dst, new Rect(new Point(64, 64), new Point(192, 192)), UniformImages.Black, Point.Origin, Op.Over);

Encode PNG

using DotImage.Png;

using var output = File.Create("output.png");
PngWriter.Encode(output, image);

Encode JPEG

using DotImage.Jpeg;

using var output = File.Create("output.jpg");
JpegWriter.Encode(output, image, new JpegOptions { Quality = 90 });

Decode GIF animation

using DotImage.Gif;

using var stream = File.OpenRead("animation.gif");
var gif = GifReader.DecodeAll(stream);

foreach (var frame in gif.Image)
{
    // process each frame
}

Project Structure

DotImage/
├── DotImage.slnx
├── src/DotImage/
│   ├── Color/           # color models, palettes, YCbCr/CMYK
│   ├── Draw/            # compositing
│   ├── Png/             # PNG codec
│   ├── Gif/             # GIF codec
│   ├── Jpeg/            # JPEG codec
│   ├── Compress/        # GIF LZW
│   ├── Util/            # YCbCr→RGBA fast paths
│   ├── Image.cs         # concrete image buffer types
│   ├── Geom.cs          # Point, Rect
│   ├── Format.cs        # FormatRegistry
│   └── ...
└── tests/DotImage.Tests/

API Mapping (Go → C#)

Relationship to Go

This library is a faithful port of Go's image tree:

Key differences from Go:

• Errors are thrown as exceptions instead of returned as error values
• Pixel buffers use byte[] (slice via Memory<byte> where applicable)
• Format registration is lazy (on first decode) instead of Go blank imports

License

The original Go source code is Copyright © The Go Authors and distributed under a BSD-style license.

This C# port retains the same license terms. See LICENSE and NOTICE for details.