Re: Reversed transform for a OCIO::DisplayTransform
Kevin Wheatley <kevin.j....@...>
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As Piotr points out this is in general not mathematically possible, in particular if any LUTs are not invertible, you'll not be able to do this. in a 1D sense imagine if you have a curve which has a turning point which results in there being multiple cases where two values of x give y having the same value, when generalised into a 3D LUT this problem becomes even more difficult to invert in a general sense even in typical outputs this is not necessarily going to give you predictable outcomes (typical for a display transform emulating another device/output especially a subtractive one like film prints or other CMY(K) outputs). These 3D luts often feature gamut compression which is where a lot of the loss comes from.
In specific cases there can be techniques to invert, but these need hand selecting, which is probably why OCIO won't do it, something like Argyll CMS or another ICC profile tool might do something for you, which might be interesting to implement, alternatively the CTL code has a scattered data interpolation code that might work.
On Fri, Apr 11, 2014 at 10:29 PM, Piotr Stanczyk <piotr.s...@...> wrote: