Darnelix.Webp 1.1.0

Darnelix.Webp

A WebP codec written entirely in C#. It decodes and encodes WebP — lossy, lossless, near-lossless, with alpha, still and animated — implemented from the published WebP container, VP8 and VP8L specifications. One managed assembly, no native code, zero runtime dependencies. This package targets .NET 8, .NET 9 and .NET 10.

What ships

• Decode. Still images (lossy VP8 and lossless VP8L, with alpha) into RGBA32, BGRA32, ARGB32, RGB24 or BGR24; cropped and scaled decode; incremental decode from bytes as they arrive; header-only feature reads; animated WebP played frame by frame onto a composited canvas.
• Encode. Still images, lossy (quality, effort, target size or PSNR, alpha quality and compression, sharp YUV, loop-filter settings) or lossless (effort, near-lossless preprocessing; the RGB under transparent pixels is always preserved); animated WebP assembled from full-canvas frames with per-frame durations, a loop count and a background colour.
• Deterministic. The same input and options produce the same bytes — with or without the optional worker threads (UseThreads on the decode and encode options, off by default).
• Defined failure. A truncated, corrupt or unsupported file raises a WebpException subtype (WebpFormatException, WebpDecodeException, WebpUnsupportedFeatureException); a bad argument raises an ArgumentException.
• SIMD-accelerated DSP kernels on every framework this package carries, each proven bit-identical to the scalar reference implementation they replace.

Two API styles cover the same functionality. The idiomatic API — WebpDecoder, WebpEncoder, WebpAnimDecoder, WebpAnimEncoder, each with an options type — exposes everything; the static Webp class mirrors the shape of the reference C API's classic entry points for the common cases (Decode, EncodeLossy, EncodeLossless, GetFeatures). Container metadata (ICC, EXIF, XMP) and animation parameters are edited with the companion command-line tool (below).

Quick start

using System;
using System.IO;
using Darnelix.Webp;
using Darnelix.Webp.Animation;
using Darnelix.Webp.Decoding;
using Darnelix.Webp.Encoding;

byte[] file = File.ReadAllBytes("input.webp");

// Header only — no pixels decoded; false (never an exception) when the bytes are not a WebP header.
if (WebpDecoder.TryGetInfo(file, out WebpImageInfo info))
{
    Console.WriteLine($"{info.Width}x{info.Height} {info.Format} alpha={info.HasAlpha} animated={info.HasAnimation}");
}

// Decode. The image owns a pooled pixel buffer: dispose it when you are done with the pixels.
using (WebpImage image = WebpDecoder.Decode(file))
{
    Span<byte> rgba = image.Pixels;   // RGBA32, top-down, 4 bytes per pixel, no row padding
    Console.WriteLine($"{image.Width}x{image.Height} {image.Format}, {rgba.Length} bytes");
}

// Encode RGBA32 pixels. The Webp facade applies the recommended defaults (effort 4, loop-filter
// strength 60, lossless alpha at effort 100); EncodeLossy takes the quality.
int width = 64, height = 64;
byte[] pixels = new byte[width * height * 4];   // RGBA32, top-down
byte[] lossless = Webp.EncodeLossless(pixels, width, height);
byte[] lossy = Webp.EncodeLossy(pixels, width, height, 85f);
File.WriteAllBytes("output.webp", lossy);

// For anything else, build the options yourself and set every field you rely on: a new
// WebpEncodeOptions starts at zero throughout, and zero means "off" for the loop filter and the
// alpha effort. Nothing is filled in for you.
var options = new WebpEncodeOptions { Quality = 85, Method = 4, FilterStrength = 60, AlphaQuality = 100, SharpYuv = true };
byte[] tuned = WebpEncoder.Encode(pixels, width, height, PixelFormat.Rgba32, options);

Animated WebP, frame by frame:

using (var animation = new WebpAnimDecoder(file))
{
    Console.WriteLine($"{animation.Info.CanvasWidth}x{animation.Info.CanvasHeight}, {animation.Info.FrameCount} frames");
    while (animation.TryGetNextFrame(out WebpFrame frame))
    {
        // frame.Pixels is the full composited canvas (RGBA32); frame.DurationMs is its display time.
    }
}

Command-line tool

The same codec drives webpx, packaged separately as Darnelix.Webp.Cli: encode, decode, inspect, edit container metadata and animation parameters, and build or extract animations from the shell.

dotnet tool install --global Darnelix.Webp.Cli
webpx encode photo.ppm photo.webp -q 90

License

Free of charge under a proprietary licence (not open source); the full terms are in LICENSE, packed with this package.

Project site: https://www.darnelix.com/products/webp-dotnet/

Support: support@darnelix.com