This error message is harmless, and you can ignore. You can solve it
by changing the image parameter in the XML description from "float"
to "int". This just selects which input is the source which doesn’t
even make much sense for this shader. You could alternately eliminate
the XML descriptions for the "image" parameter entirely to also
eliminate this harmless message. We will fix in the next release.
In order to see the saturation, please send the message "alpha ", to crossfade between the luminance (0.),
original saturation (1.), or even values outside the range of zero to
one to over/under saturate. It is just a crossfade amount between the
luminance version and original.