Map function to transform 2D image

Out:

/home/docs/checkouts/readthedocs.org/user_builds/seaborn-image/envs/v0.4.0/lib/python3.7/_collections_abc.py:841: MatplotlibDeprecationWarning:
The validate_legend_loc function was deprecated in Matplotlib 3.3 and will be removed two minor releases later.
  self[key] = other[key]

from skimage.exposure import adjust_gamma

import seaborn_image as isns

cells = isns.load_image("cells")[:, :, 32]

f = isns.imghist(cells, map_func=adjust_gamma, gamma=0.5)