Consider the following image of a knee:
By default the background of this image is the black regions on the left and right sides of the image.
But is it possible to interactively define the foreground and background of this image or any image in general so that whenever I hover the mouse on a specific portion of the image the corresponding region will be considered as the foreground and the background will become transparent?
The idea is motivated from
Healthline Bodymap (http://www.healthline.com/human-body-maps/male) and
Brain Data Crawler (http://community.wolfram.com/groups/-/m/t/568284)