is there a way to realize a GreenScreen / Chroma Keying ?
As ShaderToy does not accept custom datatypes, I am unable to easily send it the Color value of a selected point, (I added a red dot to get the custom color value of green screen). So simply find the correct color - and copy it into the shader (where it lists the BG color values).
Quite an impressive key!!! However many green screen effects pull more than one key- and also there is always an amount of spill, (as in the eyes), which needs to be fixed.
I hope this helps.
You could do a pretty basic greenscreen effect with
Mask Image with Brightness, as in the attached composition. Or maybe something better by writing GLSL in
Make Image with Shadertoy.