go-jpeg2000

A pure Go JPEG2000 codec. Decode and encode JPEG2000 codestreams (.j2k/.j2c) and JP2 files (.jp2) with zero C dependencies.

Requirements

• Go 1.25+

Installation

go get github.com/ajroetker/go-jpeg2000

Quick Start

Decoding

package main

import (
	"image/png"
	"log"
	"os"

	jpeg2000 "github.com/ajroetker/go-jpeg2000"
)

func main() {
	f, err := os.Open("input.jp2")
	if err != nil {
		log.Fatal(err)
	}
	defer f.Close()

	img, err := jpeg2000.Decode(f)
	if err != nil {
		log.Fatal(err)
	}

	out, _ := os.Create("output.png")
	defer out.Close()
	png.Encode(out, img)
}

Encoding

package main

import (
	"image"
	"image/png"
	"log"
	"os"

	jpeg2000 "github.com/ajroetker/go-jpeg2000"
)

func main() {
	f, err := os.Open("input.png")
	if err != nil {
		log.Fatal(err)
	}
	defer f.Close()

	img, _, err := image.Decode(f)
	if err != nil {
		log.Fatal(err)
	}

	out, _ := os.Create("output.j2k")
	defer out.Close()

	// Lossless encoding
	err = jpeg2000.Encode(out, img, &jpeg2000.EncodeOptions{
		Lossless: true,
	})
	if err != nil {
		log.Fatal(err)
	}
}

Automatic Format Detection

import (
	"image"
	_ "github.com/ajroetker/go-jpeg2000" // register format
)

img, format, err := image.Decode(reader) // format = "jpeg2000"

Features

Feature	Status
Decode J2K codestreams	Supported
Decode JP2 files	Supported
Encode J2K codestreams	Supported
Encode JP2 files	Supported
5/3 reversible wavelet (lossless)	Supported
9/7 irreversible wavelet (lossy)	Supported
Multi-component color transform (RCT/ICT)	Supported
EBCOT Tier-1 (MQ arithmetic coding)	Supported
EBCOT Tier-2 (packet assembly)	Supported
Rate control (PCRD-opt)	Supported
Quality layers	Supported
Grayscale and RGB images	Supported
Multi-tile images	Supported

Encode Options

type EncodeOptions struct {
	Lossless       bool      // true = 5/3 + RCT, false = 9/7 + ICT
	Quality        float64   // 0.0-1.0 (lossy only, default: 0.8)
	TargetSize     int       // target file size in bytes (overrides Quality)
	NumLayers      int       // quality layers (default: 1)
	TileWidth      int       // 0 = single tile
	TileHeight     int       // 0 = single tile
	NumResolutions int       // decomposition levels + 1 (default: 6)
	CodeBlockWidth int       // default: 64
	CodeBlockHeight int      // default: 64
	FileFormat     FileFormat // FormatJ2K or FormatJP2
}

Building

go build ./...
go test ./...
go test -bench=. -benchmem ./...

License

Apache 2.0