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OpenEXR

OpenEXR provides the specification and reference implementation of the EXR file format, the professional-grade image storage format of the motion picture industry.

The purpose of EXR format is to accurately and efficiently represent high-dynamic-range scene-linear image data and associated metadata, with strong support for multi-part, multi-channel use cases.

OpenEXR is widely used in host application software where accuracy is critical, such as photorealistic rendering, texture access, image compositing, deep compositing, and DI.

OpenEXR Project Mission

The goal of the OpenEXR project is to keep the EXR format reliable and modern and to maintain its place as the preferred image format for entertainment content creation.

Major revisions are infrequent, and new features will be carefully weighed against increased complexity. The principal priorities of the project are:

  • Robustness, reliability, security
  • Backwards compatibility, data longevity
  • Performance - read/write/compression/decompression time
  • Simplicity, ease of use, maintainability
  • Wide adoption, multi-platform support - Linux, Windows, macOS, and others

OpenEXR is intended solely for 2D data. It is not appropriate for storage of volumetric data, cached or lit 3D scenes, or more complex 3D data such as light fields.

The goals of the Imath project are simplicity, ease of use, correctness and verifiability, and breadth of adoption. Imath is not intended to be a comprehensive linear algebra or numerical analysis package.

Project Governance

OpenEXR is a project of the Academy Software Foundation. See the project's governance policies, contribution guidelines, and code of conduct for more information.

Quick Start

See the technical documentation for complete details, but to get started, the "Hello, world" exrwriter.cpp writer program is:

#include <ImfRgbaFile.h>
#include <ImfArray.h>
#include <iostream>

int
main()
{
    try {
        int width =  10;
        int height = 10;
        
        Imf::Array2D<Imf::Rgba> pixels(width, height);
        for (int y=0; y<height; y++)
            for (int x=0; x<width; x++)
                pixels[y][x] = Imf::Rgba(0, x / (width-1.0f), y / (height-1.0f));
    
        Imf::RgbaOutputFile file ("hello.exr", width, height, Imf::WRITE_RGBA);
        file.setFrameBuffer (&pixels[0][0], 1, width);
        file.writePixels (height);
    } catch (const std::exception &e) {
        std::cerr << "Unable to read image file hello.exr:" << e.what() << std::endl;
        return 1;
    }
    return 0;
}

The CMakeLists.txt to build:

cmake_minimum_required(VERSION 3.12)
project(exrwriter)
find_package(OpenEXR REQUIRED)

add_executable(${PROJECT_NAME} exrwriter.cpp)
target_link_libraries(${PROJECT_NAME} OpenEXR::OpenEXR)

To build:

$ cmake -S . -B _build -DCMAKE_PREFIX_PATH=<path to OpenEXR libraries/includes>
$ cmake --build _build

For more details, see The OpenEXR API.

Community

Resources

License

OpenEXR is licensed under the BSD-3-Clause license.

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