goexr

Go library for parsing OpenEXR files.

Not all EXR files are supported at the moment. Make sure to check the Limitations section.

Usage

Add the library as a dependency to your project.

go get github.com/mokiat/goexr/exr@latest

Parse the image as with any other format. For example:

package main

import (
	"fmt"
	"image"
	"os"

	_ "github.com/mokiat/goexr/exr"
)

func main() {
	file, err := os.Open("example.exr")
	if err != nil {
		panic(err)
	}
	defer file.Close()

	img, format, err := image.Decode(file)
	if err != nil {
		panic(err)
	}
	fmt.Printf("Bounds [%s]: %v\n", format, img.Bounds())
}

Make sure that you have added an anonymous import to the library which ensures that there is a decoder registered with the image package.

import (
  _ "github.com/mokiat/goexr/exr"
)

For more information check the Go documentation of the exr package.

Limitations

The library supports a subset of EXR files.

Supported EXR versions:

• 2

Supported image types:

• single part scanline

Supported compression modes:

• NO_COMPRESSION
• ZIP_COMPRESSION

Supported channels:

• R
• G
• B
• A

Supported channel formats:

• HALF
• FLOAT

At the time of writing, EXR images produced by the following programs appear to be supported:

• Krita
• GIMP

Tools

Aside from the exr package, this library provides two tools that can be used to check whether this project works on specific EXR files.

exrsize

This tool prints the pixel size of an EXR image.

exrsize <img.exr>

It can be install as follows:

go install github.com/mokiat/goexr/cmd/exrsize@latest

It should work with all version 2 EXR images, even those that cannot be decoded by the exr package.

exrtopng

This tool converts an exr image into a png one by using basic tone mapping and gamma correction to convert linear colors into sRGB space.

exrtopng <src.exr> <dst.png>

It can be install as follows:

go install github.com/mokiat/goexr/cmd/exrtopng@latest

This tool is subject to the above Limitations.

Resources

For the development of this decoded the following resources were useful:

• Online Documentation

    Very easy to navigate and contains information on the core concepts.
  

• PDF Documentation

    The Online Documentation appeared to have errors in some places and the PDF variant was useful in such cases.
  

• Source Code

    Some aspects of OpenEXR are not fully documented and in such cases the only place where answers can be found is the reference implementation. In fact, even the documentation refers to it at times.