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alpha channel

Posted: 04 Sep 2009, 22:33
by julius
Hi all,

I would like to extract the alpha channel of a picture, and apply it to an other picture... Can you give me the tip?

extracting alpha seems prety simple : I take any comp node, and put the output in alpha mode. But I don't know the way to go to overide the alpha of the second picture.

Thanks

Re: alpha channel

Posted: 04 Sep 2009, 23:24
by Hirazi Blue
Not sure (not an FXTree wizard), but it should be possible to limit the output (via the output options) of your second picture to RGB (instead of RGBA) and then use your extracted alpha as a matte... :-\

Re: alpha channel

Posted: 05 Sep 2009, 13:01
by Mootzoid
Hi,

it's easy and complicated at the same time, at least the solution I use:
Get a "Component Parser" and plug the picture that has the alpha that is to be replaced into input 1.
The picture with the alpha you want to use is plugged into input 2.
Then open the PPG of the "Component Parser" and enter
r[1](x,y) (for Red)
g[1](x,y) (for Green)
b[1](x,y) (for Blue)
a[2](x,y) (for Alpha)

Finished #:-s :D

Re: alpha channel

Posted: 05 Sep 2009, 15:52
by julius
Thank you very much for the tip. I just discovered a node wich can do the job easier : color adjust--> cutout (rgb+alpha)

With this one, you just have to plug your two pictures in the inputs....and that's all.

Re: alpha channel

Posted: 05 Sep 2009, 16:19
by Mootzoid
Okay, that definitely sounds easier and quicker.

Sorry I had only the :-B solution to offer ;)