For every pixel of the image, this filter holds the channel with the maximal/minimal intensity. The result is an image with only three colors, red, green and blue, and possibly pure gray.
This preview displays, in real time, the resulting image after treatment by filter.
Hold the maximal channels: For every pixel, the filter keeps intensity of the RGB color channel which has the maximal intensity and reduces other both to zero. For example: 220, 158, 175 max--> 220, 0, 0. If two channels have same intensity, both are held: 210, 54, 210 max--> 210, 0, 210.
Hold the minimal channels: For every pixel, the filter keeps intensity of the RGB color channel which has the minimal intensity and reduce both others to zero. For example: 220, 158, 175 min--> 0, 158, 0. If two minimal channels have same intensity, both are held: 210, 54, 54 min--> 0, 54, 54.
Grey levels are not changed since light intensity is the same in all three channels.