README.md

go-libjpeg

An implementation of Go binding for LibJpeg (preferably libjpeg-turbo).

The core codes are picked from go-thumber and rewritten to compatible with image.Image interface.

Usage

import "github.com/pixiv/go-libjpeg/jpeg"

func main() {
    // Decoding JPEG into image.Image
    io, err := os.Open("in.jpg")
    if err != nil {
        log.Fatal(err)
    }
    img, err := jpeg.Decode(io, &jpeg.DecoderOptions{})
    if err != nil {
        log.Fatalf("Decode returns error: %v\n", err)
    }

    // Encode JPEG
    f, err := os.Create("out.jpg")
    if err != nil {
        panic(err)
    }
    w := bufio.NewWriter(f)
    if err := jpeg.Encode(w, img, &jpeg.EncoderOptions{Quality: 90}); err != nil {
        log.Printf("Encode returns error: %v\n", err)
        return
    }
    w.Flush()
    f.Close()
}

See test code to read full features.

Features

• Raw JPEG decoding in YCbCr color.
• Decoding with color conversion into RGB/RGBA (RGBA conversion is only supported with libjpeg-turbo).
• Scaled decoding.
• Encoding from some color models (YCbCr, RGB and RGBA).

Benchmark

$ go test -bench . -benchtime 10s
...
BenchmarkDecode                     1000          26345730 ns/op
BenchmarkDecodeIntoRGB               500          30886383 ns/op
BenchmarkDecodeWithNativeJPEG        300          49815928 ns/op
...

With libjpeg-turbo:

BenchmarkDecode                     2000           9557646 ns/op
BenchmarkDecodeIntoRGB              1000          12676414 ns/op
BenchmarkDecodeWithNativeJPEG        300          45836153 ns/op

go-libjpeg is about 1.9x faster than image/jpeg. With libjpeg-turbo, it can make more faster (about 4.8x faster than image/jpeg).

Dependencies

• Go 1.6 or later.

• libjpeg (preferably libjpeg-turbo)

  DecodeIntoRGBA can only work if go-libjpeg is built with libjpeg-turbo. Because DecdeIntoRGBA uses JCS_ALPHA_EXTENSIONS. You can use DecodeIntoRGB and convert to image.RGBA if can not use libjpeg-turbo.

License

Copyright (c) 2014 pixiv Inc. All rights reserved.

See LICENSE.