[PD] chroma_key to alpha with Gem?

[cyrille henry]

Hans-Christoph Steiner a écrit :
> 
> I haven't written a shader before, anyone have one they could share? 
yes, there are some in the Gem examples.
example/10.glsl directory

> Or 
> is this possible without shaders, i.e. just Gem objects?

pix_alpha does it, but it's very basic.

pix_coloralpha can do it with other pix_objects.

Cyrille

> 
> .hc
> 
> On Apr 20, 2009, at 3:55 PM, chris clepper wrote:
> 
>> I have done a lot of this type of processing with a shader.  Just pick 
>> the color in the desired range and set the alpha of a pixel in that 
>> range to 0.  After that just lay the video on top of each other. 
>>
>> On Mon, Apr 20, 2009 at 3:34 PM, Hans-Christoph Steiner <hans at at.or.at 
>> <mailto:hans at at.or.at>> wrote:
>>
>>
>>     I was wondering whether it is possible convert a specific color,
>>     like green-screen chroma key, to alpha information using Gem.
>>      They idea is to overlap many green-screen videos.  I can see the
>>     pieces, but I can't see the whole.
>>
>>     .hc
>>
>>     ----------------------------------------------------------------------------
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