JuicyPixels-webp

Pure Haskell WebP decoder and encoder for JuicyPixels.

Features

• VP8L Lossless: Full decode and encode support
• VP8 Lossy: Full decode and encode with quality control (0-100)
• Alpha Channels: RGBA support for both lossless and lossy
• Animations: Decode and encode animated WebP files
• All Container Formats: Simple and extended WebP

Installation

stack build

Usage

Decoding

import Codec.Picture.WebP
import qualified Data.ByteString as B

-- Decode any WebP file
fileData <- B.readFile "image.webp"
case decodeWebP fileData of
  Right (ImageRGB8 img)  -> -- VP8 lossy without alpha
  Right (ImageRGBA8 img) -> -- VP8L lossless or VP8 with alpha
  Left err               -> -- Handle error

Encoding

import Codec.Picture
import Codec.Picture.WebP

-- Lossless encoding (takes Image PixelRGBA8)
let webpData = encodeWebPLossless img
B.writeFile "output.webp" webpData

-- Lossy encoding with quality (0-100, takes Image PixelRGB8)
let webpData = encodeWebPLossy img 80
B.writeFile "output.webp" webpData

-- Lossy with alpha channel (takes Image PixelRGBA8)
let webpData = encodeWebPLossyWithAlpha img 80
B.writeFile "output.webp" webpData

Animations

-- Decode animation frames
case decodeWebPAnimation fileData of
  Right frames -> mapM_ processFrame frames
  Left err     -> handleError err

-- Encode animation
let frames = [WebPEncodeFrame img1 100 0 0, WebPEncodeFrame img2 100 0 0]
let webpData = encodeWebPAnimation frames canvasWidth canvasHeight quality

Testing

stack test  # 421 tests passing

API

Decoding

• decodeWebP :: ByteString -> Either String DynamicImage
• decodeWebPFirstFrame :: ByteString -> Either String DynamicImage
• decodeWebPAnimation :: ByteString -> Either String [WebPAnimFrame]
• decodeWebPAnimationComposited :: ByteString -> Either String [Image PixelRGBA8]

Encoding

• encodeWebPLossless :: Image PixelRGBA8 -> ByteString
• encodeWebPLossy :: Image PixelRGB8 -> Int -> ByteString
• encodeWebPLossyWithAlpha :: Image PixelRGBA8 -> Int -> ByteString
• encodeWebPAnimation :: [WebPEncodeFrame] -> Int -> Int -> Int -> ByteString

Documentation

• docs/webp-format.md - VP8L lossless specification
• docs/vp8-bitstream.md - VP8 lossy specification
• STATUS.md - Current implementation status
• PLAN.md - Original implementation plan (historical)

License

BSD-3-Clause