pura-webp

A pure Ruby WebP decoder and encoder with zero C extension dependencies.

Part of the pura-* series — pure Ruby image codec gems.

Features

• VP8 lossy WebP decoding
• VP8L lossless WebP encoding
• No native extensions, no FFI, no external dependencies
• CLI tool included

Installation

gem install pura-webp

Usage

require "pura-webp"

# Decode
image = Pura::Webp.decode("photo.webp")
image.width      #=> 800
image.height     #=> 600
image.pixels     #=> Raw RGB byte string
image.pixel_at(0, 0) #=> [r, g, b]

# Encode (VP8L lossless)
Pura::Webp.encode(image, "output.webp")

# Resize
thumb = image.resize(200, 200)
Pura::Webp.encode(thumb, "thumb.webp")

Benchmark

Decode performance on a 400×400 WebP image, Ruby 4.0.2 + YJIT:

Operation	pura-webp	ffmpeg (C + SIMD)	vs ffmpeg
Decode	207 ms	66 ms	3.1× slower

Why pure Ruby?

• gem install and go — no brew install webp, no apt install libwebp-dev
• Works everywhere Ruby works — CRuby, ruby.wasm, mruby, JRuby, TruffleRuby
• Edge/Wasm ready — browsers (ruby.wasm), sandboxed environments
• No system library needed — unlike every other Ruby WebP solution

Current Limitations

• Decoder: VP8 lossy only (VP8L lossless and VP8X extended not yet decoded)
• Encoder: VP8L lossless format, works best with images up to ~200×200
• Loop filter not implemented in decoder (slight quality difference)

Related Gems

Gem	Format	Status
pura-jpeg	JPEG	✅
pura-png	PNG	✅
pura-bmp	BMP	✅
pura-gif	GIF	✅
pura-tiff	TIFF	✅
pura-ico	ICO	✅
pura-webp	WebP	✅
pura-image	All formats	✅

License

MIT — see LICENSE.

The VP8 decoder is a Ruby port of the Go package golang.org/x/image/vp8, which is distributed under the BSD-3-Clause license. See LICENSE-GO for that notice. The Go copyright is retained on the ported files as required.