Re: [Openexr-devel] OpenEXR files with nonlinearly encoded RGB

[Karl Rasche]

> The specific question was whether photographic image editors should allow writing nonlinearly encoded RGB data to OpenEXR files, or whether instead the RGB data should be converted to a linear gamma ICC profile before being exported as OpenEXR.
>
> In the usual photographic workflow, editing operations are performed directly on the RGB data to intentionally modify the scene-linear nature of the raw data that was captured by the camera. From the photographer's point of view, whether data should be exported as linear or nonlinear RGB depends on why the photographer wants to export the data.

I'd say that irrespective of your image state, or the processing you want to perform, you should be writing linear rgb into openexr files. Otherwise, there are likely all sorts of interop landmines that will be stepped upon.

There are some places, like lossy compressors, where data is assumed to be linear and transformed i to a perceptual space. Storing nonlinear data, and not marking the channels as 'pLinear', will yield less than ideal results. That said, this flag is really meant for things like color differences, and should not be interpreted as encouraging the storage of nonlinear rgb.