Program sfmask | Create a mask.
[SYNOPSIS]
sfmask < in.rsf > out.rsf min= max= min= max=
[COMMENTS]

Mask is an integer data with ones and zeros. 
Ones correspond to input values between min and max.

The output can be used with sfheaderwindow.

[PARAMETERS]
int     | max | = |   | 	maximum header value 
int     | min | = |   | 	minimum header value 
[DIRECTORY]
system/main
