For most workflows that use a 3D LUT to render extended dynamic range images, it is not necessary to reverse the operation on the picked color. Your application should just look up the un-transformed pixel value from the image (not the displayed frame buffer), based on the selection position.

It would be *very* handy if your application would render the various color pickers and swatches through the OCIO display transform as well. Photoshop does not do this. 

On Friday, April 11, 2014 10:24:38 AM UTC-7, Dmitry Kazakov wrote:

Hi, all!

I am a developer of Krita [0] painting application and we use OCIO for displaying wide range images. I'm having a bit of a problem now. Since we are a painting application, we need to be able not only to display a color on screen (which we do using DisplayTransform), but also to pick an already displayed color back into app (for usage in color selectors or for drag-and-dropped colors). So, effectively, I need to get a reversed transform for a DisplayTransform. But it seems to be explicitly prohibited (it throws an exception in the case). I'm wondering, is it possible to get a reversed transform for a DisplayTransform without reimplementing it completely using GroupTransform?

Thank you in advance!

[0] - krita.org

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Dmitry Kazakov

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