OpenEXR is a high dynamic-range (HDR) image file format developed by Industrial Light & Magic for use in computer imaging applications
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OpenEXR is a high dynamic-range (HDR) image file format developed by Industrial Light & Magic (ILM) for use in computer imaging applications. It supports stereoscopic and deep images. 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. The file format has seen wide adoption in a number of industries.

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, including all contributions, is released under a modified BSD license. Please see the LICENSE file accompanying the distribution for the legal fine print.

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 - Standard image viewing programs
  • Contrib - Various plugins and utilities, contributed by the community.

Please see the README files of each of the individual directories for more information.

A collection of OpenEXR images is available from the adjacent repository openexr-images.


OpenEXR depends on zlib.

PyIlmBase depends on boost-python and optionally on numpy.

In OpenEXR_Viewers:

  • exrdisplay depends on fltk
  • playexr depends on Cg

Web Resources

Main web page: http:://

GitHub repository:

Mail lists:

Building and Installation

Download the latest release of OpenEXR from

To build the OpenEXR binaries from source, compile and install the individual sub-models (IlmBase, PyIlmBase, OpenEXR, OpenEXR_Viewers), according to the instructions in the respective README files. Build and install the IlmBase module first, then build and install the OpenEXR module. Optionally, then build and install PyIlmBase, OpenEXR_Viewers, and Contrib.

For the basic installation:

cd <source root>/IlmBase
make install

cd <source root>/OpenEXR
make install

See the module README files for options to configure.

Building from Git

Alternatively, you can download the latest release or the lastest development branch directly from

After cloning the repo locally, generate the configuration scripts by running the bootstrap script:

cd <source root>/IlmBase
make install

cd <source root>/OpenExr
make install

Building from git and bootstrap requires that autoconf is installed. Download and install it from

Building with CMake

Alternatively, you can build with cmake, version 3.11 or newer.

In the root CMakeLists.txt file, with -D options on the cmake line, or by using a tools such as ccmake or cmake-gui, configure the OpenEXR build. The options are detailed below.

Create a source root directory, cd into it, and run cmake to configure the build. Select an appropriate generator, such as "Unix Makefiles", or "Visual Studio 15 2017 Win64". Then run make a the root directory; this will build the appropriate submodules, according to the settings of the cmake options, described below.

cmake -DCMAKE_INSTALL_PREFIX=<install location> <OpenEXR source root> -G "selected generator" -DCMAKE_PREFIX_PATH=<paths to dependencies - zlib etc>

The available options are:

  • OPENEXR_BUILD_ILMBASE (ON) By default, IlmBase is always built.

  • OPENEXR_BUILD_OPENEXR (ON) By default, OpenEXR is always built.

  • OPENEXR_BUILD_PYTHON_LIBS (ON) By default, the Python bindings will be built.

  • OPENEXR_BUILD_VIEWERS (OFF) By default, the viewers are not built, as they have not been updated for modern OpenGL.


  • OPENEXR_BUILD_STATIC (OFF) The build can be configured to create either shared libraries, or static libraries, or both.

  • OPENEXR_NAMESPACE_VERSIONING (ON) OpenEXR symbols will be contained within a namespace

  • OPENEXR_FORCE_CXX03 (OFF) C++03 compatibility is possible as an option

  • OPENEXR_ENABLE_TESTS (ON) By default, the tests will be built.

  • OPENEXR_RUN_FUZZ_TESTS (OFF) By default, the damaged input tests will NOT be run, due to their long running time. If you wish to run them as part of "make test" (or equivalent in your build system), then enable this. A "make fuzz" target will be available to run the fuzz test regardless.

  • OPENEXR_PYTHON_MAJOR, OPENEXR_PYTHON_MINOR "2", "7" By default, OpenEXR is built against Python 2.7.x.


Documentation is available at