golibjpegturbo

README

Read JPEG images in Go, quickly

This library is the fastest possible way to decode and encode JPEG images in Go.

We achieve this via cgo bindings to libjpeg-turbo library.

The exact speed depends on the image and CPU. On Mac Book Pro, compared to image/jpeg standard library, golibjpegturbo is:

• 6x faster when decoding
• 1.7x faster when encoding at quality level of 90%

You can rerun the benchmark on your machine with go test -bench=.

Additionally, unlike image/jpeg, this library can read JPEG images in CMYK format.

Setup

Before you import library, you need to install libjpeg-turbo.

On Ubuntu: sudo apt-get install libjpeg-turbo8-dev.

On Mac OS X: brew install libjpeg-turbo

Usage

go get github.com/kjk/golibjpegturbo

The API is the same as image/libjpeg:

import "golibjpegturbo"

func decode(r io.Reader) (image.Image, error) {
    return golibjpegturbo.Decode(r)
}

func encode(img image.Image) ([]byte, error) {
    options := &golibjpegturbo.Options{Quality: 90}
    var buf bytes.Buffer
    err = golibjpegturbo.Encode(&buf, decodedImg, options)
    if err != nil {
        return nil, err
    }
    return buf.Bytes(), nil
}

More docs: http://godoc.org/github.com/kjk/golibjpegturbo

Running a stress test

There's a stress test. If you have a directory with images, you can do go run stress_test/main.go -dir=$directory.

The test loops infinitely and decodes/encodes the images to verify there are no problems caused by incorrect cgo usage.

License

MIT.

Written by Krzysztof Kowalczyk. Inspired by lye/libjpeg and go-thumber.

Documentation

Overview

Package golibjpegturbo is the fastest way to decode and encode JPEG images in Go.

We achieve this via cgo bindings to http://libjpeg-turbo.virtualgl.org library.

The exact speed depends on the image and CPU. On Mac Book Pro, compared to image/jpeg standard library, golibjpegturbo is:

* 6x faster when decoding

* 1.7x faster when encoding at quality level of 90%

Before you import library, you need to install libjpeg-turbo.

On Ubuntu: sudo apt-get install libjpeg-turbo8-dev.

On Mac OS X: brew install libjpeg-turbo

Index

• Constants
• func Decode(r io.Reader) (image.Image, error)
• func DecodeData(d []byte) (img image.Image, err error)
• func Encode(w io.Writer, m image.Image, o *Options) (err error)
• type JpegInfo
  • func GetJpegInfo(d []byte) (info *JpegInfo, err error)
• type Options

Constants

const DefaultQuality = 75

DefaultQuality is the default quality encoding parameter.

Functions

func Decode

func Decode(r io.Reader) (image.Image, error)

Decode reads a JPEG image from r and returns it as an image.Image.

func DecodeData

func DecodeData(d []byte) (img image.Image, err error)

DecodeData reads JPEG image from d and returns it as an image.Image.

func Encode

func Encode(w io.Writer, m image.Image, o *Options) (err error)

Encode writes the Image m to w in JPEG 4:2:0 baseline format with the given options. Default parameters are used if a nil *Options is passed.

Types

type JpegInfo

type JpegInfo struct {
	Components       int
	ColorSpace       int
	Width            int
	Height           int
	ColorSpaceString string
}

JpegInfo contains information about JPEG image.

func GetJpegInfo

func GetJpegInfo(d []byte) (info *JpegInfo, err error)

GetJpegInfo returns information about a JPEG image.

type Options

type Options struct {
	Quality int
}

Options are the encoding parameters. Quality ranges from 1 to 100 inclusive, higher is better.