rename contrasts module to views
create contrasts module
convert luminance function to method of LightDark Class
modify compose method to work with contrast module

external function calculates contrast value and returns Image with
contrast values instead of channel value (3>1). This is calcualted with
np.histogram

only two for testing reason
subclassing a subcalls of numpy was hard due to the use of __new__ and
__array_finalize__
max recursion errors appear now after multiple use of derive. Do I need
numpy's __del__ method?

just as a reference implementation for the value contrast and not generacilly

reference implementation for Movie, Frames class
scatterplot contrast without plot as function in contrasts module
helper functions in helpers module