%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
%ROA（Ratio?of?Average）?operator?used?in?SAR?image?processing%
%?????????????????????Edge?Detection????????????????????????%
%??????????????????????????3x3??????????????????????????????%
%?INPUT:?gray?scale?picture?????????????????????????????????%??
%?OUTPUT:?Edge?detection?result?&?operator?output???????????%
%?USAGE:?[edgeoperator_output]=roa3（input）?????????????????%
%?Code?by?Flesher???Harbin?Institute?of?Technology??????????%
%????????????????????May?20th?2009?????????????????????????%
%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%

function?[outputr]=roa3（pic）
pic=double（pic）;
[M?N]=size（pic）;
output=zeros（[M?N]）;
threshold=0.8;
r=ones（[M?N]）;
for?i=1:M
????for?j=1:N
????????if?i>=2?&&?i<=M-1?&&?j>=2?&&?j<=N-1
????????????%angle=0
????????????u1=mean（pic（i-1j-1:j+1））;
????????????u2=mean（pic（i+1j-1:j+1））