turbo

README

Turbo (TurboJPEG Go wrapper)

This is a very thin wrapper around turbojpeg.

Why not use https://github.com/pixiv/go-libjpeg ?

Because go-libjpeg is built to use the libjpeg-compatible API of either libjpeg or libjpeg-turbo. That API does not allow one to specify the chroma sub-sampling, so you're unable to compress to 4:2:0. That was the sole reason for building this package -- to enable compression to 420 chroma sub-sampling.

This wrapper links explicitly to TurboJPEG. There is no fallback to libjpeg.

How to use

import "github.com/bmharper/turbo"

func compressImage(width, height int, rgba []byte) {
	raw := turbo.Image{
		Width: width,
		Height: height,
		Stride: width * 4,
		RGBA: rgba,
	}
	params := turbo.MakeCompressParams(turbo.PixelFormatRGBA, turbo.Sampling420, 35, 0)
	jpg, err := turbo.Compress(&raw, params)
}

func decompressImage(jpg []byte) (*Image, error) {
	return turbo.Decompress(jpg)
}

Documentation

Index

• func Compress(img *Image, params CompressParams) ([]byte, error)
• type CompressParams
  • func MakeCompressParams(pixelFormat PixelFormat, sampling Sampling, quality int, flags Flags) CompressParams
• type Flags
• type Image
  • func Decompress(encoded []byte) (*Image, error)
• type PixelFormat
• type Sampling

Functions

func Compress

func Compress(img *Image, params CompressParams) ([]byte, error)

Types

type CompressParams

type CompressParams struct {
	PixelFormat PixelFormat
	Sampling    Sampling
	Quality     int // 1 .. 100
	Flags       Flags
}

func MakeCompressParams

func MakeCompressParams(pixelFormat PixelFormat, sampling Sampling, quality int, flags Flags) CompressParams

type Flags

type Flags C.int

const (
	FlagAccurateDCT   Flags = C.TJFLAG_ACCURATEDCT
	FlagBottomUp      Flags = C.TJFLAG_BOTTOMUP
	FlagFastDCT       Flags = C.TJFLAG_FASTDCT
	FlagFastUpsample  Flags = C.TJFLAG_FASTUPSAMPLE
	FlagNoRealloc     Flags = C.TJFLAG_NOREALLOC
	FlagProgressive   Flags = C.TJFLAG_PROGRESSIVE
	FlagStopOnWarning Flags = C.TJFLAG_STOPONWARNING
)

type Image

type Image struct {
	Width  int
	Height int
	Stride int
	Pixels []byte
}

func Decompress

func Decompress(encoded []byte) (*Image, error)

type PixelFormat

type PixelFormat C.int

const (
	PixelFormatRGB     PixelFormat = C.TJPF_RGB
	PixelFormatBGR     PixelFormat = C.TJPF_BGR
	PixelFormatRGBX    PixelFormat = C.TJPF_RGBX
	PixelFormatBGRX    PixelFormat = C.TJPF_BGRX
	PixelFormatXBGR    PixelFormat = C.TJPF_XBGR
	PixelFormatXRGB    PixelFormat = C.TJPF_XRGB
	PixelFormatGRAY    PixelFormat = C.TJPF_GRAY
	PixelFormatRGBA    PixelFormat = C.TJPF_RGBA
	PixelFormatBGRA    PixelFormat = C.TJPF_BGRA
	PixelFormatABGR    PixelFormat = C.TJPF_ABGR
	PixelFormatARGB    PixelFormat = C.TJPF_ARGB
	PixelFormatCMYK    PixelFormat = C.TJPF_CMYK
	PixelFormatUNKNOWN PixelFormat = C.TJPF_UNKNOWN
)

type Sampling

type Sampling C.int

const (
	Sampling444  Sampling = C.TJSAMP_444
	Sampling422  Sampling = C.TJSAMP_422
	Sampling420  Sampling = C.TJSAMP_420
	SamplingGray Sampling = C.TJSAMP_GRAY
)