Gamma correction masktool expression

[bxyhxyh]

I need to use masktool for gamma correction. But I'm not experienced to write masktool expression.

Please convert it to masktool syntax.

Levels(0,2.5,255,0,255,coring=false)

[feisty2]

search "LUT" on google

[bxyhxyh]

I searched mt_lut gamma correction. But I couldn't find good result.

[Gavino]

Please convert it to masktool syntax.
Levels(0,2.5,255,0,255,coring=false)
mt_lut("x 255 / 1 2.5 / ^ 255 *", chroma="copy")
The expression corresponds to ((x/255)^(1/2.5))*255.

[bxyhxyh]

mt_lut("x 255 / 1 2.5 / ^ 255 *", chroma="copy")
The expression corresponds to ((x/255)^(1/2.5))*255.
Thanks,
How it would be for coring=true case?

[Gavino]

That was for the coring=false case, which is what you asked for before.

For coring=true, it would be:
mt_lut(yexpr="x 16 - 219 / 0 max 1 min 1 2.5 / ^ 219 * 16 +", expr="x 16 max 240 min", chroma="process")

or perhaps clearer:
mt_lut(yexpr=mt_polish("min(max((x-16)/219, 0), 1)^(1/2.5) * 219 + 16"), expr=mt_polish("min(max(x,16),240)", chroma="process")