A numeric matrix with three columns corresponding to red, green, blue, with numerical
values ranging from 0 to 255 to be combined numerically with c2.mat.
c2.mat
A numeric matrix with three columns corresponding to red, green, blue, with numerical
values ranging from 0 to 255 to be combined numerically with c1.mat.
combine_method
Method of combining colors, can be 'scaled_geomean',
'standard'/'euclidean', 'negative_euclidean', 'mean', 'scaled_geomean'
(default = 'scaled_geomean')
max_per_channel
Maximal color value per RGB channel (default 255).