function [x1,y1,flag]=GetMV2(x0,y0,m,n,size)
%正方形四步搜索
global CURIMAGE PREIMAGE
m=m*2;
n=n*2;
Point=struct('x',0,'y',0,'diff',0);
MatchPoint=struct('x',0,'y',0,'nextP',[0,0,0.01]);
toComparePoint(1:8)=MatchPoint;

A=Point;
A.x=x0;
A.y=y0;
A.diff=GetDiff(A, A);

flag=0;

matchBlock=MatchPoint ;

matchBlock.x=x0;
matchBlock.y=y0;
matchBlock.nextP=A;

%初始化待匹配點
toMatchPoint(1).x=A.x;
toMatchPoint(1).y=A.y+2;%*16;
toMatchPoint(2).x=A.x+2;%*16;
toMatchPoint(2).y=A.y;	
toMatchPoint(6).x=A.x;
toMatchPoint(6).y=A.y-2;%*16;
toMatchPoint(7).x=A.x-2;%*16;
toMatchPoint(7).y=A.y;toMatchPoint(3).x=A.x-1;%*16;
toMatchPoint(3).y=A.y-1;%*16;		
toMatchPoint(4).x=A.x+1;%*16;
toMatchPoint(4).y=A.y-1;%*16;		
toMatchPoint(5).x=A.x-1;%*16;
toMatchPoint(5).y=A.y+1;%*16;	
toMatchPoint(8).x=A.x+1;%*16;
toMatchPoint(8).y=A.y+1;%*16;

%記錄搜索次數
state=0;
while state<20
    state=state+1;
    if state==1
		for i=1:8		
			%如果超過邊界,繼續下一個循環	
            if toMatchPoint(i).x>(m-1)*size | toMatchPoint(i).x<1 | toMatchPoint(i).y>(n-1)*size | toMatchPoint(i).y<1 
                continue;%如果超過邊界,繼續下一個循環
			else
			    toMatchPoint(i).diff=GetDiff(A,toMatchPoint(i));	
			    %尋找Diff最小的點
			    if toMatchPoint(i).diff<matchBlock.nextP.diff 
				    matchBlock.nextP.diff=toMatchPoint(i).diff;
				    matchBlock.nextP.x=toMatchPoint(i).x;
				    matchBlock.nextP.y=toMatchPoint(i).y;
                end
            end
        end
 
     %如果中心點為最小
     elseif matchBlock.x==matchBlock.nextP.x & matchBlock.y==matchBlock.nextP.y	
			%更新搜索窗口的中心點
			matchBlock.x=matchBlock.nextP.x;
			matchBlock.y=matchBlock.nextP.y;
			matchBlock.diff=matchBlock.nextP.diff;
		
			%計算所有點的Diff值,并找到Diff最小的點
			toMatchPoint(1).x=matchBlock.x+1;%*16;
			toMatchPoint(1).y=matchBlock.y;
			toMatchPoint(2).x=matchBlock.x-1;%*16;
			toMatchPoint(3).y=matchBlock.y;
	
			toMatchPoint(3).x=matchBlock.x;
			toMatchPoint(3).y=matchBlock.y-1;%*16;
			toMatchPoint(4).x=matchBlock.x;
			toMatchPoint(4).y=matchBlock.y+1;%*16;
            
			for i=1:4
			%尋找Diff最小的點
				if toMatchPoint(i).x>(m-1)*size | toMatchPoint(i).x<1 | toMatchPoint(i).y>(n-1)*size | toMatchPoint(i).y<1  
                    continue;%如果超過邊界,繼續下一個循環
				else
					toMatchPoint(i).diff=GetDiff(A,toMatchPoint(i));
                  
					if toMatchPoint(i).diff<matchBlock.nextP.diff
						matchBlock.nextP.diff=toMatchPoint(i).diff;
						matchBlock.nextP.x=toMatchPoint(i).x;
						matchBlock.nextP.y=toMatchPoint(i).y;
                    end				
                end
            end
            %diff=matchBlock.nextP.diff
			break;	%計算運動矢量完成
            
    %如果中心點不為最小
    else
 		%更新搜索窗口的中心點
	    matchBlock.x=matchBlock.nextP.x;
		matchBlock.y=matchBlock.nextP.y;
		matchBlock.diff=matchBlock.nextP.diff;
        toMatchPoint=SettoMatchPoint(matchBlock);
        %計算所有點的Diff值,并找到Diff最小的點
        for i=1:8
		%尋找Diff最小的點
			if toMatchPoint(i).x>(m-1)*size | toMatchPoint(i).x<1 | toMatchPoint(i).y>(n-1)*size | toMatchPoint(i).y<1  
                continue;   %如果超過邊界,繼續下一個循環
			else
				toMatchPoint(i).diff=GetDiff(A,toMatchPoint(i));
				if toMatchPoint(i).diff<matchBlock.nextP.diff
					matchBlock.nextP.diff=toMatchPoint(i).diff;
					matchBlock.nextP.x=toMatchPoint(i).x;
					matchBlock.nextP.y=toMatchPoint(i).y;
                 end				
             end
         end
    end
    
end

%未找到運動矢量，說明是剛出現的點
if state>=25 | matchBlock.diff>32
    flag=1;
end

x1=matchBlock.nextP.x-x0;
y1=matchBlock.nextP.y-y0;


function diffRes=GetDiff(point1, point2,size)

global CURIMAGE PREIMAGE
diffRes=0;
A=PREIMAGE(point1.x:(point1.x+size-1),point1.y:(point1.y+size-1));
B=CURIMAGE(point2.x:(point2.x+15),point2.y:(point2.y+size-1));

C=A-B;
diffRes=sum(C(:));


function [toMatchPoint]=SettoMatchPoint(A)
    toMatchPoint(1).x=A.x;
    toMatchPoint(1).y=A.y+2;%*16
	
	toMatchPoint(2).x=A.x+2;%*16
	toMatchPoint(2).y=A.y;
	
	toMatchPoint(3).x=A.x-1;%*16
	toMatchPoint(3).y=A.y-1;%*16
		
	toMatchPoint(4).x=A.x+1;%*16
	toMatchPoint(4).y=A.y-1;%*16
		
	toMatchPoint(5).x=A.x-1;%*16
	toMatchPoint(5).y=A.y+1;%*16
	
	toMatchPoint(6).x=A.x;
	toMatchPoint(6).y=A.y-2;%*16
	
	toMatchPoint(7).x=A.x-2;%*16
	toMatchPoint(7).y=A.y;
    toMatchPoint(8).x=A.x+1;%*16
    toMatchPoint(8).y=A.y+1;%*16