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

Used In
		GEO384H          hw4/invint   RSF          challenge/rain