webp-rs

A Rust library to encode and decode WebP images via statically-linked libwebp.

⬇️ Installation

This library can be installed using Cargo. To do that, run the following command in your project's root directory:

cargo add webp-rs

The crate links as webp, so you import it with use webp; regardless of the package name.

[!NOTE] The first build downloads the prebuilt static binaries for your platform, so an internet connection is required (see Troubleshooting for offline builds).

🤖 Usage

Here are some examples of how to encode and decode WebP images using this library. These snippets don't have any error handling for the sake of simplicity, but you should always check for errors in production code.

Encoding

let img = image::open("/path/to/image.png").unwrap(); // an image to be encoded
let bytes = webp::encode(&img).unwrap(); // encode the image with default settings
std::fs::write("/path/to/image.webp", &bytes).unwrap(); // save the WebP to a file

Encoding with custom settings

use webp::WebpEncoder;

let img = image::open("/path/to/image.png").unwrap();
let mut bytes = Vec::new();
img.write_with_encoder(
    WebpEncoder::new(&mut bytes)
        .with_quality(80)      // 0–100, higher = better quality
        .with_compression(6)   // 0–6, higher = more effort, smaller file
        .with_threads(true),   // enable multi-threaded encoding
).unwrap();

Lossless encoding

use webp::WebpEncoder;

let img = image::open("/path/to/image.png").unwrap();
let mut bytes = Vec::new();
img.write_with_encoder(WebpEncoder::new(&mut bytes).with_lossless(true)).unwrap();

Decoding

let bytes = std::fs::read("/path/to/image.webp").unwrap(); // read the WebP file
let img = webp::decode(&bytes).unwrap(); // decode it into a DynamicImage
img.save("/path/to/image.png").unwrap(); // save it in another format

Probing (header only)

Read the image dimensions and color type without decoding the pixels — useful for validation or thumbnailing pipelines:

let bytes = std::fs::read("/path/to/image.webp").unwrap();
let info = webp::probe(&bytes).unwrap();
println!("{}x{} ({:?})", info.width, info.height, info.color_type);

The public API also exposes [encode_buffer] (encode a typed ImageBuffer directly), [WebpEncoder] / [WebpDecoder] for image-trait integration, [EncoderConfig] / [DecoderConfig] for full control, and [libwebp_version].

Encoder settings

WebP is an 8-bit format: inputs are encoded as 8-bit RGB/RGBA (grayscale is expanded automatically) and decoded back to the same. 16-bit inputs are rejected as unsupported.

Runnable examples

The examples/ directory has standalone programs covering each part of the API, runnable out of the box against the bundled assets:

cargo run --example encode          # encode with defaults
cargo run --example decode          # decode a WebP to PNG
cargo run --example custom_encoder  # WebpEncoder builder (quality/compression/threads)
cargo run --example encode_buffer   # encode a typed ImageBuffer
cargo run --example probe           # read the header without decoding pixels
cargo run --example roundtrip       # encode then decode
cargo run --example lossless        # lossless encoding via EncoderConfig
cargo run --example parallel_encode # concurrent encoding
cargo run --example version         # print the linked libwebp version

💣 Troubleshooting

My build fails because it can't download the binaries

The first build fetches the prebuilt static libraries for your platform over the network. For offline or air-gapped builds, download the archive for your target from binaries-webp, extract it, and point the build at it with the WEBP_BINARIES_DIR environment variable:

$ WEBP_BINARIES_DIR=/path/to/extracted/libs cargo build

📝 License

webp-rs is released under the Apache 2.0 License. See LICENSE for details.

👨🏾‍💻 Author

Vinicius Egidio (vinicius.io)