Marti wrote:
>> I'm scratching my head over how to invert a LUT.
>
> Mike,
>
> That is indeed a very difficult topic. For properly inverting a LUT
> you have to know the gamut boundaries, and then proceed differently
> inside or outside gamut. I have done some experimentation with
> generalized Newton on n dimensions using Jacobians. Works well if the
> gamut hull is convex and the lut is "smooth" enough. You have to
> extrapolate ouside gamut. I have used
> a polinomial approach here, with little succes I should add :-(
>
> lcms does not have such code, there is no need to do that strictly
> following ICC
> spec. However, I would be interesting as a future addition, since
> this would solve
> the issue about limited precission BToAxx tags exhibit...

Thanks for your answer - is this then a generally unsolved problem, or do
proprietary solutions exist?

Mike Russell
www.curvemeister.com
www.geigy.2y.net




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