libwebp

libwebp, the WebP image codec, through C++23 modules.

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libwebp 1.5.0 decodes and encodes WebP: lossy (VP8) and lossless (VP8L), with alpha, still and animated. The upstream C API is unchanged: WebPGetInfo, WebPDecodeRGBA, WebPEncodeRGBA, WebPEncodeLosslessRGBA, WebPEncode with WebPConfig and WebPPicture, WebPAnimEncoder and WebPAnimDecoder are the upstream globals of the headers. The codec is compat.libwebp 1.5.0. The headers' static inline functions (WebPConfigInit, WebPPictureInit, WebPGetFeatures …) are adapted under the same names, and the macros are constants. On every CI run the bytes written and the pixels read are those of upstream's own cwebp and dwebp, and pinned hashes hold on every target, the Web included.

Modules

• import mcpplibs.mwrap.libwebp;: decoding (webp/decode.h), encoding (webp/encode.h), WebPData and the animation enums (webp/mux_types.h), re-exporting the two below
• import mcpplibs.mwrap.libwebp.sharpyuv;: libsharpyuv, the sharp RGB to YUV conversion (SharpYuvConvert …)
• import mcpplibs.mwrap.libwebp.macros;: WEBP_MAX_DIMENSION, the ABI versions, WEBP_ABI_IS_INCOMPATIBLE … in mcpplibs::mwrap::libwebp::macros
• import mcpplibs.mwrap.libwebp.demux;: WebPDemux, WebPAnimDecoder, with the demux feature
• import mcpplibs.mwrap.libwebp.mux;: WebPMux, WebPAnimEncoder, with the mux feature

More Modules API -> Usage and API

Getting started

mcpp new pictures --template mcpplibs.mwrap.libwebp@1.5.0
cd pictures
mcpp run

The default template encodes a picture with alpha lossy at three qualities and lossless, decodes each back to RGBA and prints its size and PSNR. The animation template (--template mcpplibs.mwrap.libwebp@1.5.0:animation) encodes frames with WebPAnimEncoder and plays them back with WebPAnimDecoder.

[dependencies]
"mcpplibs.mwrap.libwebp" = "1.5.0"

import std;
import mcpplibs.mwrap.libwebp;

int main() {
    std::vector<std::uint8_t> rgba(64 * 64 * 4, 200);   // a light grey, opaque square
    std::uint8_t* webp = nullptr;
    const std::size_t size = WebPEncodeRGBA(rgba.data(), 64, 64, 64 * 4, 80.f, &webp);  // lossy, quality 80
    int width = 0, height = 0;
    std::uint8_t* pixels = WebPDecodeRGBA(webp, size, &width, &height);
    std::println("{} bytes, {} x {}", size, width, height);
    WebPFree(pixels);
    WebPFree(webp);
}

Feature	Effect
demux	libwebpdemux (compat.libwebp's src/demux) and the demux module: WebPDemux*, WebPAnimDecoder*
mux	libwebpmux (compat.libwebp's src/mux) and the mux module: WebPMux*, WebPAnimEncoder*

Neither is on by default. Animated WebP needs demux to read and mux to write.

The codec

compat.libwebp builds the release's src/dec, src/enc, src/dsp, src/utils and sharpyuv (and src/demux, src/mux with the features) with SSE2 on x86-64 and NEON on arm64, SSE4.1 off, and without WEBP_USE_THREAD: thread_level and use_threads are accepted and run on the calling thread. Its output is deterministic: the same picture and settings give the same bytes on Linux, macOS, Windows and wasm32-emscripten, with GCC or LLVM, dev or release, and the same bytes as upstream's cwebp. Details and limits: docs/usage.md.

Examples

• examples/webpcodec: decodes WebP to PPM/PAM, encodes PPM/PAM to WebP (lossy or lossless) and prints a file's features, written against the module; tools/run_conformance.py compares it with upstream's cwebp and dwebp.

Build and testing

Linux (x86_64 GCC and LLVM, arm64 GCC), macOS, Windows and wasm32-emscripten (under node) CI build the modules and run the tests in the dev and release profiles, with and without the features; the native rows also run the export audit (tools/check_exports.py: the generated modules are fresh, every declaration exported, every macro mapped or excluded with its reason) and, but on Windows, the conformance run against upstream's tools. A separate job scaffolds both templates as an installed package and runs them.

License

Apache-2.0 for the wrapper, by mcpp-community; libwebp remains BSD-3-Clause with Google's patent grant (upstream/libwebp/COPYING, upstream/libwebp/PATENTS).