Pixel value clipping?

[fjhdavid]

I have an YV12 clip with values going from 32 to 235. so when I watch the clip, "black part of the clip" look a little bit grey (value=32 instead of 16).

I would like like to get real black, so I just want to apply the following filter:

for all pixel values >32, new pixel value will stay as they are
for all pixel values <32, new pixel value will be set to 16

Is it possible?

Thanks

Francois

[Manao]

mt_masktools : mt_lut("x 32 < 16 x ?", chroma="copy")

[fjhdavid]

Thank you!

I just downloaded the Masktools and I look into your documentation.

chroma="copy" means this parameter leave the chroma as it is?

Francois

[Manao]

Yes (it's documented under "common parameters")

[fjhdavid]

Manao,

After looking with photoshop, there is a problem with my script (trying to use your suggestion).
My script is:

x=last
y=mt_lut("x 32 < 16 x ?", chroma="copy")
mergeluma(y)

and "black pixel" are still grey.

Where did I made a mistake in my script?

thanks
Francois

PS: of course I want to apply this filter only on Y (and not on U and V)

[thetoof]

Not exactly an answer to your question, but I'd recommend smoothlevels if you want to go full PC range (looks better imo than simply replacing values to get "real greys").

[fjhdavid]

sorry for my thread and my question, I found the solution...

The script was ok but my "bad pixels" were just Y=34...then the limit of 32 was not sufficient.

Manao, thanks for this function mt_lut !

Francois

[Manao]

x=last
y=mt_lut("x 32 < 16 x ?", chroma="copy")
mergeluma(y)Just do :mt_lut("x 32 < 16 x ?", chroma="copy")

[IanB]

@fjhdavid,

Look into Histogram(), ColorYUV(Analyze=True) or RGBAdjust(Analyze=True) to see the luma distribution of your source.

You probable want to stretch the luma range rather than just declare a hard limit. Something like a simple :-Levels(16, 1.0, 255, 0, 255, False)or one of the many related methods.