.INPUT FILE: VOL001
[Enter the name of the input file.]
.OUTPUT FILE: VOL002
[Enter name for output file.]
NOTES
Image/volume is "circularly closed" so that pixels on
boundaries have a neighbor on opposite boundary.
Gradient is sum of difference of intensity between 8
neighboring pixels and the central pixel under a kernal
weighted by inverse distance from the central pixel.
The gradient magnitude is obtained with 'CE G' whereas
'CE GX' gives magnitude of the 'X' component of the
gradient vector, etc.