``umbra'' -- compute the umbra of a volume

purpose:

Reduce the gray-scale value of all voxels by the value of the user-preset intensity cutoff. All voxels that drop below 0 are set to zero. This is the grayscale umbra function that appears in gray-scale mathematical morphology.

input:

An 8-bit volume.

output:

An 8-bit volume.

parameters:

Default parameters menu is

umbra inten. cutoff = 0
* input from vol # = 0
* copy output to vol # = 0
*

comments:

1. A very fast function.

Updated: Fri May 19 14:39:07 CDT