function?[usvs]?=?HSoptflow（Xrgbn）
%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
%?Author:?Gregory?Power?gregory.power@wpafb.af.mil
%?This?MATLAB?code?shows?a?Motion?Estimation?map?created?by
%?using?a?Horn?and?Schunck?motion?estimation?technique?on?two
%?consecutive?frames.??Input?requires.
%?????Xrgb（hwdN）?where?X?is?a?frame?sequence?of?a?certain
%????????????????height（h）?width?（w）?depth?（d=3?for?color）?
%????????????????and?number?of?frames?（N）.?
%?????n=?is?the?starting?frame?number?which?is?less?than?N?
%?????V=?the?output?variable?which?is?a?2D?velocity?array
%
%?Sample?Call:?V=HSoptflow（X3）;
%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
[hwdN]=size（Xrgb）
if?n>N-1
???error（1‘requested?file?greater?than?frame?number?required‘）;
end;?
%get?two?image?frames
if?d==1
????Xn=double（Xrgb（::1n））;
????Xnp1=double（Xrgb（::1n+1））;
elseif?d==3
????Xn=double（Xrgb（::1n）*0.299+Xrgb（::2n）*0.587+Xrgb（::3n）*0.114）;
????Xnp1=double（Xrgb（::1n+1）*0.299+Xrgb（::2n+1）*0.587+Xrgb（::3n+1）*0.114）;
else
????error（2‘not?an?RGB?or?Monochrome?image?file‘）;
end;

%get?image?size?and?adjust?for?border
size（Xn）
hm5=h-5;?wm5=w-5;
z=zeros（hw）;?v1=z;?v2=z;