Code Quality Rank: L1
Programming language: C++
Tags: Image Processing    
Latest version: v2.4.0

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OpenEXR is a high dynamic-range (HDR) image file format for use in computer imaging applications. It supports stereoscopic and deep images. OpenEXR's features include:

  • Higher dynamic range and color precision than existing 8- and 10-bit image file formats.
  • Support for 16-bit floating-point, 32-bit floating-point, and 32-bit integer pixels. The 16-bit floating-point format, called "half", is compatible with the half data type in NVIDIA's Cg graphics language and is supported natively on their GPUs.
  • Multiple image compression algorithms, both lossless and lossy. Some of the included codecs can achieve 2:1 lossless compression ratios on images with film grain. The lossy codecs have been tuned for visual quality and decoding performance.
  • Extensibility. New compression codecs and image types can easily be added by extending the C++ classes included in the OpenEXR software distribution. New image attributes (strings, vectors, integers, etc.) can be added to OpenEXR image headers without affecting backward compatibility with existing OpenEXR applications.
  • Support for stereoscopic image workflows and a generalization to multi-views.
  • Flexible support for deep data: pixels can store a variable-length list of samples and, thus, it is possible to store multiple values at different depths for each pixel. Hard surfaces and volumetric data representations are accommodated.
  • Multipart: ability to encode separate, but related, images in one file. This allows for access to individual parts without the need to read other parts in the file.
  • Versioning: OpenEXR source allows for user configurable C++ namespaces to provide protection when using multiple versions of the library in the same process space.

OpenEXR is a project of the Academy Software Foundation. It was originally developed by Industrial Light & Magic (ILM) in 2003. Weta Digital, Walt Disney Animation Studios, Sony Pictures Imageworks, Pixar Animation Studios, DreamWorks, and other studios, companies, and individuals have made contributions to the code base.

OpenEXR Sub-Modules

The OpenEXR distribution consists of the following sub-modules:

  • IlmBase - Utility libraries from Industrial Light & Magic: Half, Imath, Iex, IlmThread.
  • PyIlmBase - Python bindings for the IlmBase libraries.
  • OpenEXR - The core image library.
  • OpenEXR_Viewers - Example code for image viewing programs.
  • Contrib - Various plugins and utilities, contributed by the community.

A collection of OpenEXR images is available from the adjacent repository https://github.com/openexr/openexr-images.

Supported Platforms

OpenEXR builds on:

  • Linux
  • macOS
  • Microsoft Visual Studio 2015 or newer

The Python bindings in PyIlmBase support Python 2 and Python 3.

Developer Quick Start

See [INSTALL](INSTALL.md) for instructions on downloading and building OpenEXR from source.


Getting Help

There are two primary ways to connect with the OpenEXR project:

  • The openexr-dev@lists.aswf.io mail list: This is a development focused mail list with a deep history of technical conversations and decisions that have shaped the project. Subscribe at openexr-dev@lists.aswf.io.

  • GitHub Issues: GitHub issues are used both to track bugs and to discuss feature requests.

See [CONTRIBUTING](CONTRIBUTING.md) for more information.

Getting Involved

OpenEXR welcomes contributions to the project. See [CONTRIBUTING](CONTRIBUTING.md) for more information about contributing to OpenEXR.


OpenEXR is released under the [BSD-3-Clause](LICENSE) license.

See [PATENTS](OpenEXR/PATENTS) for license information about portions of OpenEXR that are provided under a different license.

Project Goverance

OpenEXR is governed by the Academy Software Foundation. See [GOVERNANCE](GOVERNANCE.md) for more infomation about how the project operates.

Frequently Asked Questions

  • "pip install openexr doesn't work."

The OpenEXR project provides python bindings for the Imath vector/matrix classes, but it does not provide python bindings for reading, writing, or editing .exr files. The openexrpython module is not affiliated with the OpenEXR project or the ASWF. Please direct questions there.

Alternatively, OpenImageIO also includes python bindings for OpenEXR.


*Note that all licence references and agreements mentioned in the OpenEXR README section above are relevant to that project's source code only.