finalcanny.m

canny边缘检测算子,可以对灰度数字图象的弱边缘进行很好的检测

%SEGMENTATION STEP

%NON MAXIMAL SUPPRESSION AND HYSTERESIS
%Input - Gaussian smoothed image
%      - Edge image           
%      - High threshold
%      - Low threshold
%Output- Thinned image 


function [imnew1]=finalcanny(imnew1,edge,high,low)

[m,n]=size(edge);

for i=1:m,
    for j=1:n,
        
        % adjascent pixel calculation
        
         if edge(i,j)==0
             if j>1 
                lt=imnew1(i,j-1);
             else
                lt=edge(i,j);
%                   lt=0;
             end
             if j<n
                rt=imnew1(i,j+1);
             else
                rt=edge(i,j);
%                 rt=0;

             end
         elseif edge(i,j)==45
             if i<m & j>1
                 lt=imnew1(i+1,j-1);
             else
                 lt=edge(i,j);
%                 lt=0;

             end
             if i>1 &j<n
                 rt=imnew1(i-1,j+1);
             else 
                 rt=edge(i,j);
%                 rt=0;
             end
         elseif edge(i,j)==90
             if i>1
                 lt=imnew1(i-1,j);
             else
                 lt=edge(i,j);
%                 lt=0;
             end
             if i<m
                 rt=imnew1(i+1,j);
             else
                 rt=edge(i,j);
%                     rt=0;
             end
         else
             if i>1 & j>1
                 lt=imnew1(i-1,j-1);
             else
                 lt=edge(i,j);
%                 lt=0;

             end
             if i<m & j<n
                 rt=imnew1(i+1,j+1);
             else
                 rt=edge(i,j);
%                     rt=0;
             end
         end
         
       %hysteresis calculation
       
       if(imnew1(i,j) <= lt | imnew1(i,j) <= rt) 
           imnew1(i,j)=0;
       else 
           
%          high =30;
% 		 low =15 ;
                 high =high;
		         low =low ;
 

		 if imnew1(i,j) >= high
		     imnew1(i,j) = 255; % edge 

         elseif imnew1(i,j) < low
		     imnew1(i,j) = 0; 
             
         else
             % magnitude is between high & low determine the 8 pixels
             p1=0;p2=0;p3=0;p4=0;p5=0;p6=0;p7=0;p8=0;
             
             if i>1 & j>1
                 p1=imnew1(i-1,j-1);
             end
             if i>1
                 p2=imnew1(i-1,j);
             end
             if i>1 & j<n
                 p3=imnew1(i-1,j+1);
             end
             if j>1
                 p4=imnew1(i,j-1);
             end
             if j<n
                 p5=imnew1(i,j+1);
             end
             if i<m & j>1
                 p6=imnew1(i+1,j-1);
             end
             if i<m
                 p7=imnew1(i+1,j);
             end
             if i<m & j<n
                 p8=imnew1(i+1,j+1);
             end
             
            if p1>high | p2>high | p3>high | p4>high | p5>high | p6>high | p7>high | p8>high
                imnew1(i,j)=255;
            else
                imnew1(i,j)=0;
            end
            
        end
    end
end
end