REMOVE OUTLIERS

Removes extremely dark and extremely bright speckled pixels (known as salt
and pepper noise).  Works by replacing each extreme pixel with the median
value of pixels within a neighborhood of pixels.  This should be done before
any smoothing.

Percent:
Upper bottom and lower percentile of pixels to replace.  (Value is in % so
inputting 0.1 means 0.1% not 1%).

Size:
Size of window [pixels^2] to find a median value from.  A size of 3 means
that a 3x3 window centered on the outlier pixel will be used to find a
median value.