go-libwebp

A implementation of Go binding for libwebp.

Forked from tidbyt/go-libwebp, which itself was forked from harukasan/go-libwebp.

Dependencies

No external dependencies are needed, as this module includes the source code of libwebp 1.3.2. This has the advantage that you don't need to install any header files or SDKs. libwebp is automatically built by the go toolchain (With CGO), no matter the platform or architecture.

For this to work you need a working CGO environment, which means you need to have GCC (or another CGO compatible compiler) installed.

Also, please open an issue if you need support for a newer version of libwebp.

Usage

The examples directory contains example codes and images.

Decoding WebP into image.RGBA

package main

import (
	"github.com/tidbyt/go-libwebp/test/util"
	"github.com/tidbyt/go-libwebp/webp"
)

func main() {
	var err error

	// Read binary data
	data := util.ReadFile("cosmos.webp")

	// Decode
	options := &webp.DecoderOptions{}
	img, err := webp.DecodeRGBA(data, options)
	if err != nil {
		panic(err)
	}

	util.WritePNG(img, "encoded_cosmos.png")
}

You can set more decoding options such as cropping, flipping and scaling.

Encoding WebP from image.RGBA

package main

import (
	"bufio"
	"image"

	"github.com/Dadido3/go-libwebp/test/util"
	"github.com/Dadido3/go-libwebp/webp"
)

func main() {
	img := util.ReadPNG("cosmos.png")

	// Create file and buffered writer
	io := util.CreateFile("encoded_cosmos.webp")
	w := bufio.NewWriter(io)
	defer func() {
		w.Flush()
		io.Close()
	}()

	config := webp.ConfigPreset(webp.PresetDefault, 90)

	// Encode into WebP
	if err := webp.EncodeRGBA(w, img.(*image.RGBA), config); err != nil {
		panic(err)
	}
}

Encoding animations from a series of frames

package main

import (
	"image"
	"time"

	"github.com/Dadido3/go-libwebp/test/util"
	"github.com/Dadido3/go-libwebp/webp"
)

func main() {
	// Get some frames
	img := []image.Image{
		util.ReadPNG("butterfly.png"),
		util.ReadPNG("checkerboard.png"),
		util.ReadPNG("yellow-rose-3.png"),
	}

	// Initialize the animation encoder
	width, height := 24, 24
	anim, err := webp.NewAnimationEncoder(width, height, 0, 0)
	if err != nil {
		panic(err)
	}
	defer anim.Close()

	// Add each frame to the animation
	for i, im := range img {
		// all frames of an animation must have the same dimensions
		cropped := im.(interface {
			SubImage(r image.Rectangle) image.Image
		}).SubImage(image.Rect(0, 0, width, height))

		if err := anim.AddFrame(cropped, 100*time.Millisecond); err != nil {
			panic(err)
		}
	}

	// Assemble the final animation
	buf, err := anim.Assemble()
	if err != nil {
		panic(err)
	}

	// Write to disk
	f := util.CreateFile("animation.webp")
	defer f.Close()
	f.Write(buf)
}

TODO

• Incremental decoding API

License

Copyright (c) 2016 MICHII Shunsuke. All rights reserved.

This library is released under The BSD 2-Clause License. See LICENSE.