[Openexr-devel] OpenEXR files with nonlinearly encoded RGB

[Elle Stone]

Hi all,

I'm involved with GIMP development as it pertains to ICC profile color 
management. GIMP is primarily used for processing photographic images 
and for creating digital art.

We are having a discussion about whether it's OK to read and write 
OpenEXR RGB files that aren't encoded using linear gamma RGB data.

Some of us have argued that:

* OpenEXR is a data container.
* Nothing in the OpenEXR specifications forbids reading or writing 
non-linearly encoded RGB data.
* After opening the file in an ICC profile color managed editing 
application, it should be up to the user to assign the correct ICC 
profile to interpret the data.

Others have maintained that statements in the OpenEXR documentation such 
as "By convention, OpenEXR stores scene-referred linear values in the 
RGB floating-point numbers" (Technical Introduction to OpenEXR) should 
be interpreted to mean that OpenEXR RGB data should always be encoded as 
linear gamma data, and that reading and writing of non-linearly encoded 
RGB data shouldn't be supported.

We were hoping you all could shed some light on this question.

Thanks in advance for advice as to whether there really is a requirement 
that OpenEXR RGB data always be encoded linearly.

Elle Stone
--
http://ninedegreesbelow.com
Color management and free/libre photography