colorex.cex_lut : color_lookup_table tensorflow port allowing for exact control over lut and coordinate broadcasting

Color lookup table op forked and modified from: https://github.com/tensorflow/probability/tree/master/tensorflow_probability/python/math/interpolation.py

colorex.cex_lut.color_lookup_table(x, x_ref_min, x_ref_max, y_ref, axis=- 4, fill_value='constant_extension', name=None)

apply a batch of 3d lookup tables to a batch of color tensors. the following shapes are expected to work:

N: batch size D: lookup table cube size ( lut total element count is D*D*D*3 ) HW: number of colors in a batch ( probably flattened image height*width ) x: shape [N,HW,3] x_ref_min: shape [N,3] x_ref_max: shape [N,3] y_ref: shape [N,D,D,D,3]