Install¶
The OpenEXR library is available for download and installation in binary form via package managers on many Linux distributions. See https://pkgs.org/download/openexr for a complete list. The common ones that generally provide current releases include:
Beware that some distributions are out of date and only provide distributions of outdated releases OpenEXR. We recommend against using OpenEXR v2, and we strongly recommend against using OpenEXR v1.
On macOS, we do not recommend installation via HomeBrew because the distribution is outdated.
Also note that the official OpenEXR project does not provide supported
python bindings. pip install openexr
installs the openexrpython module, which is not
affiliated with the OpenEXR project or the ASWF. Please direct
questions there.
Build from Source¶
OpenEXR builds on Linux, macOS, Microsoft Windows via CMake, and is cross-compilable on other systems.
Download the source from the GitHub releases page page, or clone the repo.
The release
branch of the repo always points to the most advanced
release.
Prerequisites¶
Make sure these are installed on your system before building OpenEXR:
OpenEXR requires CMake version 3.12 or newer
C++ compiler that supports C++11
zlib
Imath (auto fetched by CMake if not found)
The instructions that follow describe building OpenEXR with CMake.
Note that as of OpenEXR 3, the Gnu autoconf bootstrap/configure build system is no longer supported.
Linux/macOS¶
To build via CMake, you need to first identify three directories:
The source directory, i.e. the top-level directory of the downloaded source archive or cloned repo, referred to below as
$srcdir
A temporary directory to hold the build artifacts, referred to below as
$builddir
A destination directory into which to install the libraries and headers, referred to below as
$installdir
.
To build: .. code-block:
$ cd $builddir
$ cmake $srcdir --install-prefix $installdir
$ cmake --build $builddir --target install --config Release
Note that the CMake configuration prefers to apply an out-of-tree
build process, since there may be multiple build configurations
(i.e. debug and release), one per folder, all pointing at once source
tree, hence the $builddir
noted above, referred to in CMake
parlance as the build directory. You can place this directory
wherever you like.
See the CMake Configuration Options section below for the most common
configuration options especially the install directory. Note that with
no arguments, as above, make install
installs the header files in
/usr/local/include
, the object libraries in /usr/local/lib
, and the
executable programs in /usr/local/bin
.
Windows¶
Under Windows, if you are using a command line-based setup, such as
cygwin, you can of course follow the above. For Visual Studio, cmake
generators are “multiple configuration”, so you don’t even have to set
the build type, although you will most likely need to specify the
install location. Install Directory By default, make install
installs the headers, libraries, and programs into /usr/local
, but you
can specify a local install directory to cmake via the
CMAKE_INSTALL_PREFIX
variable:
$ cmake .. -DCMAKE_INSTALL_PREFIX=$openexr_install_directory
Library Names¶
By default the installed libraries follow a pattern for how they are named. This is done to enable multiple versions of the library to be installed and targeted by different builds depending on the needs of the project. A simple example of this would be to have different versions of the library installed to allow for applications targeting different VFX Platform years to co-exist.
If you are building dynamic libraries, once you have configured, built, and installed the libraries, you should see the following pattern of symlinks and files in the install lib folder:
libOpenEXR.so -> libOpenEXR-3_1.so
libOpenEXR-3_1.so -> libOpenEXR-3_1.so.30
libOpenEXR-3_1.so.30 -> libOpenEXR-3_1.so.30.3.0
libOpenEXR-3_1.so.30.3.0 (the shared object file)
The -3_1
suffix encodes the major and minor version, which can be
configured via the OPENEXR_LIB_SUFFIX
CMake setting. The 30
corresponds to the so version, or in libtool
terminology the
current
shared object version; the 3 denotes the libtool
revision
, and the 0
denotes the libtool
age
. See the
libtool
documentation for more details.
Imath Dependency¶
OpenEXR depends on Imath. If a suitable
installation of Imath cannot be found, CMake will automatically
download it at configuration time. To link against an existing
installation of Imath, add the Imath directory to the
CMAKE_PREFIX_PATH
setting:
$ mkdir $build_directory
$ cd $build_directory
$ cmake -DCMAKE_PREFIX_PATH=$imath_install_directory \
-DCMAKE_INSTALL_PREFIX=$openexr_install_destination \
$openexr_source_directory
$ cmake --build . --target install --config Release
Alternatively, you can specify the Imath_DIR
variable:
$ mkdir $build_directory
$ cd $build_directory
$ cmake -DImath_DIR=$imath_config_directory \
-DCMAKE_INSTALL_PREFIX=$openexr_install_destination \
$openexr_source_directory
$ cmake --build . --target install --config Release
Note that Imath_DIR
should point to the directory that includes
the ImathConfig.cmake
file, which is typically the
lib/cmake/Imath
folder of the root install directory where Imath
is installed.
See below for other customization options.
Porting Applications from OpenEXR v2 to v3¶
See the OpenEXR/Imath 2.x to 3.x Porting Guide for details about differences from previous releases and how to address them. Also refer to the porting guide for details about changes to Imath.
Building the Documentation¶
The OpenEXR technical documentation at https://openexr.readthedocs.io is generated via Sphinx with the Breathe extension using information extracted from header comments by Doxygen.
To build the documentation locally from the source headers and
.rst
files, set the CMake option BUILD_DOCS=ON
. This adds
Doxygen
and Sphinx
CMake targets and enables building the docs
by default. generation is off by default.
Building the documentation requires that sphinx
, breathe
, and
doxygen
are installed. It further requires the sphinx-press-theme, as indicated in the
requirements.txt
file.
See the doxygen downloads page for how to install it. Binary distributions are available for many systems, so you likely do not need to build from source. On Debian/Ubuntu, for example:
$ sudo apt-get install doxygen
Similarly, see the sphinx installation page for how to install it. On Debian/Ubuntu:
$ sudo apt-get install python3-sphinx
And to install sphinx-press-theme:
$ pip3 install sphinx_press_theme
Note that the https://openexr.readthedocs.io
documentation takes the place of the formerly distributed .pdf
documents in the docs
folder, although readthedocs supports
downloading of documentation in pdf format, for those who prefer it
that way.
CMake Build-time Configuration Options¶
The default CMake configuration options are stored in
cmake/OpenEXRSetup.cmake
. To see a complete set of option
variables, run:
$ cmake -LAH $openexr_source_directory
You can customize these options three ways:
Modify the
.cmake
files in place.Use the UI
cmake-gui
orccmake
.Specify them as command-line arguments when you invoke cmake.
Library Naming Options¶
OPENEXR_LIB_SUFFIX
Append the given string to the end of all the OpenEXR libraries. Default is
-<major>_<minor>
version string. Please see the section on library names
Imath Dependency¶
CMAKE_PREFIX_PATH
The standard CMake path in which to search for dependencies, Imath in particular. A comma-separated path. Add the root directory where Imath is installed.
Imath_DIR
The config directory where Imath is installed. An alternative to using
CMAKE_PREFIX_PATH
. Note thatImath_DIR
should be set to the directory that includes theImathConfig.cmake
file, which is typically thelib/cmake/Imath
folder of the root install directory.
Namespace Options¶
OPENEXR_IMF_NAMESPACE
Public namespace alias for OpenEXR. Default is
Imf
.OPENEXR_INTERNAL_IMF_NAMESPACE
Real namespace for OpenEXR that will end up in compiled symbols. Default is
Imf_<major>_<minor>
.OPENEXR_NAMESPACE_CUSTOM
Whether the namespace has been customized (so external users know)
IEX_NAMESPACE
Public namespace alias for Iex. Default is
Iex
.IEX_INTERNAL_NAMESPACE
Real namespace for Iex that will end up in compiled symbols. Default is
Iex_<major>_<minor>
.IEX_NAMESPACE_CUSTOM
Whether the namespace has been customized (so external users know)
ILMTHREAD_NAMESPACE
Public namespace alias for IlmThread. Default is
IlmThread
.ILMTHREAD_INTERNAL_NAMESPACE
Real namespace for IlmThread that will end up in compiled symbols. Default is
IlmThread_<major>_<minor>
.ILMTHREAD_NAMESPACE_CUSTOM
Whether the namespace has been customized (so external users know)
Component Options¶
BUILD_TESTING
Build the testing tree. Default is
ON
. Note that this causes the test suite to be compiled, but it is not executed. To execute the suite, run “make test”.OPENEXR_RUN_FUZZ_TESTS
Controls whether to include the fuzz tests (very slow). Default is
OFF
.OPENEXR_BUILD_TOOLS
Build and install the binary programs (exrheader, exrinfo, exrmakepreview, etc). Default is
ON
.OPENEXR_INSTALL_EXAMPLES
Build and install the example code. Default is
ON
.
Additional CMake Options¶
See the CMake documentation for more information (https://cmake.org/cmake/help/v3.12/).
CMAKE_BUILD_TYPE
For builds when not using a multi-configuration generator. Available values:
Debug
,Release
,RelWithDebInfo
,MinSizeRel
BUILD_SHARED_LIBS
This is the primary control whether to build static libraries or shared libraries / dlls (side note: technically a convention, hence not an official
CMAKE_
variable, it is defined within cmake and used everywhere to control this static / shared behavior)OPENEXR_CXX_STANDARD
C++ standard to compile against. This obeys the global
CMAKE_CXX_STANDARD
but doesn’t force the global setting to enable sub-project inclusion. Default is14
.CMAKE_CXX_COMPILER
The C++ compiler.
CMAKE_C_COMPILER
The C compiler.
CMAKE_INSTALL_RPATH
For non-standard install locations where you don’t want to have to set
LD_LIBRARY_PATH
to use themCMAKE_EXPORT_COMPILE_COMMANDS
Enable/Disable output of compile commands during generation. Default is
OFF
.CMAKE_VERBOSE_MAKEFILE
Echo all compile commands during make. Default is
OFF
.
Cross Compiling / Specifying Specific Compilers¶
When trying to either cross-compile for a different platform, or for tasks such as specifying a compiler set to match the VFX reference platform, cmake provides the idea of a toolchain which may be useful instead of having to remember a chain of configuration options. It also means that platform-specific compiler names and options are out of the main cmake file, providing better isolation.
A toolchain file is simply just a cmake script that sets all the
compiler and related flags and is run very early in the configuration
step to be able to set all the compiler options and such for the
discovery that cmake performs automatically. These options can be set
on the command line still if that is clearer, but a theoretical
toolchain file for compiling for VFX Platform 2015 is provided in the
source tree at cmake/Toolchain-Linux-VFX_Platform15.cmake
which
will hopefully provide a guide how this might work.
For cross-compiling for additional platforms, there is also an
included sample script in cmake/Toolchain-mingw.cmake
which shows
how cross compiling from Linux for Windows may work. The compiler
names and paths may need to be changed for your environment.
More documentation:
Ninja¶
If you have Ninja installed, it is faster than make. You can generate ninja files using cmake when doing the initial generation:
$ cmake -G “Ninja” ..