pura-webp

A pure Ruby WebP decoder and encoder without additional image-processing libraries.

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

• VP8 lossy WebP decoding
• VP8L lossless WebP encoding
• No image-specific native extension or FFI dependency
• CLI tool included

gem install pura-webp

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")

These historical measurements include ffmpeg process startup. They do not compare against an in-process C codec or establish Rails pipeline throughput.

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

• gem install and go — no brew install webp, no apt install libwebp-dev
• No system library needed — unlike every other Ruby WebP solution

• 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)

Images contain 8-bit RGB pixels. The encoder produces VP8L, which this decoder cannot read back yet. Decoded pixels are RGB and do not retain alpha. Multi-partition VP8 frames are also unsupported.

crop(x, y, width, height) requires integer coordinates, positive dimensions, and a region entirely inside the image; invalid regions raise ArgumentError.

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.