====== Median ======
Median replaces each pixel with the median value of the pixels in the neighborhood around it.
  * The default neighborhood is 3 × 3 pixels.
  * With one number, the neighborhood is a square of that width.
  * The width and height must be odd. An even number is changed to the next larger odd number.

The input can be byte, integer or floating point, and the output is the same type as the input.