OpenColorIO is Sony Imagework's open source colour management framework geared toward professional visual effects and film work. It has not been universally adopted by Linux, so it works well for the applications that tap into it, and is otherwise ignored.
If you carefully manage your colourspace and colour profiles, OpenColorIO is a must-have. If you take the stance that “close enough is good enough”, then OpenColorIO will likely not be useful to you directly, but it's easy to install and is worth having.
As it is a system-wide colour management framework, applications can incorporate OpenColorIO and inherit the ability to open files without colourspace conversion.
It shouldn't be, but careful colour management is actually a niche technology. Few applications actually leverage OpenColorIO, and fewer of those are open source.
Install OpenColorIO from http://slackbuilds.org.
OpenColorIO is not something you use direcly; it's a framework for applications to incorporate. It is very likely that you have very few applications on your system that choose to do that (yet), but in VFX work it's common within the high-end applications like Natron and Krita and Blender.
OpenColorIO does ship with some useful userspace utilities, however, which may be useful.
Since OpenColorIO deals largely with colour look-up tables (called a “LUT”), essentially a colour profile definition for moving images (see the Colourspace section for more information), most configuration for OpenColorIO is just keeping track of what LUT goes with what shot or scene.
Color profile management in OpenColorIO is generally done in the file system and system environment, somewhat akin to
.htaccess files in an Apache web server, or
.git directories in Git projects. A file, called
config.ocio may be stored in a shot's project directory (see planter for a possible solution).
Just as you might store a specific ICC profile for a set of images, or synth patches for a song, or fonts for a design, store LUTs in a logical location along with a shot or a project.
The OpenColorIO config page contains several sample
config.ocio files for you to use or adapt.
For the full config file syntax, read http://opencolorio.org/userguide/config_syntax.html.
ociobakelut (LUT Conversion)
A common problem in VFX is that the colourspace of motion pictures is defined by LUTs, while the colorspace of still images use ICC profiles. This means that if you, for example, move a matte painting or texture from GIMP to Blender or Natron, you are dealing with two different definitions of colour.
OpenColorIO includes the
ociobakelut tool that can create an ICC profile (which can be used in GIMP) from a LUT.
First, you should know your display's profile. If you are doing this kind of colour matching, then you will have generated your own profile with ColorHug or similar.
Create an ICC from a LUT:
$ ociobakelut --format icc --inputspace vd16 \ --outputspace srgb8 \ --displayicc /path/to/myCustomProfile.icc \ --description "vd16-to-srgb8" --copyright "cc-0"
Once you have your new ICC profile, load it into GIMP by way of the Edit → Preferences menu → Colour Management panel.
For more information on the
ociobakelut tool, see the OpenColorIO Official Documentation.
Converting images from one colourspace to another can be done with the OpenColorIO tool
ocioconvert foo_0033.exr vd16 foo_033aces.exr aces
A simple proof-of-concept viewer with several handy keyboard shortcuts that make it an unexpectedly useful tool. Use it to view images, and adjust the image with just a few keystrokes to get a good overview of how the image might look in a different colourspace or with different adjustments.
It's only a preview tool, so none of your changes can be saved, but it's useful for quick analysis, or to instantly view an image within a different colourspace.