Program sfextract | Forward interpolation in 2-D slices. 
[SYNOPSIS]
sfextract < in.rsf > out.rsf head=head.rsf xkey=0 ykey=1 interp=2
[PARAMETERS]
file    | head | = |   | 	auxiliary input file name
int     | interp | =2 |  [1,2] | 	interpolation method, 1: nearest neighbor, 2: bi-linear 
int     | xkey | =0 |   | 	x key number 
int     | ykey | =1 |   | 	y key number 
[DIRECTORY]
system/generic
