Re: OpenEXR files with nonlinearly encoded RGB

Elle,

The intent is very much that of a scene linear encoded data for colour data
in an OpenEXR file.
Of course, you can put anything in there you like, but of the applications
I am aware of all will interpret the data as linear,  scene referred.

Out of interest, what is your motivation for wanting to encode exr files
with a non-trivial gamma?

Piotr


On 20 February 2015 at 12:45, Elle Stone <[email protected]>
wrote:

> 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
>
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