OpenMaya plugin use texture as color input

[mvn882]

Hey,
I'm trying to write a plugin that takes the color out from a file texture as input.
I'm using the new openmaya api in python and just cant get it to work even just setting the output to the input just results in all black pixels, maybe im doing something wrong:
I'm doing the following:

OpenMaya.MFnNumericAttribute()
numeric_attr_fn.createColor(...)
then taking the input asFloatVector()
and setting the output with setMFloatVector(...)

I also tried adding UV coordinates which seemed to do something as it's now calling compute for each pixel it seems but still just outputs (0,0,0).
anybody have experience with this? thanks!

[mvn882]

After messing around with it more I found I have to make an MPxShadingNodeOverride for it to work, not the most elegant solution though 😕

[revoconner]

I tried to implement your solution but it didnt work, I am still getting black, trying to make a reconstruct blue channel node for normal maps that are packed to only R and G.
Any pointer in the right direction would be helpful @mvn882