图像处理：边缘提取的ROA算子方法实现3X3

%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
%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））