Dimensionality Reduction: set bv pixels in the output as bv
I observe the manual states:
Background Value -bv float Background value to ignore in computation of the transformation matrix. Note that all pixels will still be processed when applying the transformation.
I think this a wrong choice: pixels with bv values in the input should be set as bv in the output.
Also, bv values should be ignored for calculating the input min,max values for rescaling (not sure they are, just in case)