From: Steinar H. Gunderson <sgunderson@bigfoot.com>
Date: Sat, 28 Sep 2013 22:16:48 +0000 (+0200)
Subject: Clip below-zero (out-of-gamut) colors in LiftGammaGainEffect.
X-Git-Tag: 1.0~115
X-Git-Url: https://git.sesse.net/?p=movit;a=commitdiff_plain;h=58e7b9a8164bdaad7b0c698b2d0d80db53d79a5c;hp=58e7b9a8164bdaad7b0c698b2d0d80db53d79a5c

Clip below-zero (out-of-gamut) colors in LiftGammaGainEffect.

pow(x, y) for x < 0 is undefined, and behaves differently on nVidia
and Intel. This can reasonably happen when having inputs from a different
gamut, or just a complex chain before the LGG effect; there's nothing
in Movit that prohibits out-of-sRGB-gamut colors. Thus, we need to detect
such inputs and clamp them.

We could in theory check for the special case of y=1 (no gamma change)
and allow negative values through then, but this wouldn't seem like a good
solution, especially if animating gamma.

Found and debugged by Christophe Thommeret.
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