Rearranges the color channels of one or two input images into the output image.
I.e., takes two inputs and allows you to return an output where any of the Red, Green, Blue and Alpha channels are swapped or set to any of the channels from the input.
Essentially it allows you to pack and swap RGB channels in any possible way. Grayscale inputs are treated as if they are Color: Red, Green, Blue and Alpha all return the same values.