this modules serves to compute a loss function to guide non-linear optimisation
of module parameters. to this end, it reads an input buffer with some processing applied
to it. this is then compared against the reference image.
after computing the loss, it will be stored (cpu side) in a parameter loss.
input: the processed imageorig: the reference imagedspya display channel to output the masked pixels that are considered during loss computation
bound: only pixels within these bounds are considered in the loss. pixel brightness has to be> bound.x,< bound.yand saturation (i.e. max channel minus min channel) has to be< bound.z.loss: the computed loss will be stored here if download sink was enabled during graph processing.