[PD] some GEM questions ...

[Peter P.]

* oliver <oliver at klingt.org> [2017-04-12 14:21]:
> hi, dear list !
> 
> i'm looking for an insight into some questions i ran into recently when i
> decided to give GEM a serious shot after all.
> please be patient, i'm probably spoiled by JITTER ...
> 
> PD 0.47.1
> GEM 0.93.3
> WINDOWS 7/64bit
> 
> 1.) is there a way to do image processing (i.e. levels, contrast,
> satturation etc.) on the GPU ?
> 
> as far as i understood [pix_...] objects do all their processing with the
> CPU
> and others like [color] do it in openGL (thus GPU), is that right ?
> now, for big textures (1280x720 or bigger) that would be the preferable way
> of manipulating things, right ?
Asking a similar question recently on this list I got told that a lot is
possible using shaders. See if you have a folder named 10.glsl on your
OS somewhere that could hold Gem examples for shaders. 

Searching the mailing list archive
https://lists.puredata.info/pipermail/pd-list/
for "shaders"
https://lists.puredata.info/search?P=shaders&G=Pd-list&HITSPERPAGE=20&SORT=-1
might give you results as well.
 
> 2.) i'm looking for objects that do "compositing", i.e. ways to overlay two
> pix sources. apart from the ones existing (add, multiplay, subtract, mix) ,
> i would love to have the well-known (AE,vegas, etc.) compositing modes like
> "darken", "lighten", "dodge" "difference" etc. - but also chromakeying !
> 
> is this possible ? and is it possible to do in opengl rather than with a
> [pix_] object ?

Look for help patches
	12.blending.pd
	13.maskDancer.pd
	14.takeAlpha.pd
	15.pix_alpha.pd

and the [pix_chroma_key] object and its documentation perhaps.