Ring_label2.m

      % Find edges using the Canny operator with hysteresis thresholds of 0.1
    % and 0.2 with smoothing parameter sigma set to 1.
%      Explain: The Canny method finds edges by looking for local maxima of the
%        gradient of I. The gradient is calculated using the derivative of a
%        Gaussian filter. The method uses two thresholds, to detect strong
%        and weak edges, and includes the weak edges in the output only if
%        they are connected to strong edges. This method is therefore less
%        likely than the others to be "fooled" by noise, and more likely to
%        detect true weak edges.
    edgeim = edge(im,'canny', T_edge, 1);

    % figure(1), imshow(edgeim);

        % Link edge pixels together into lists of sequential edge points, one
    % list for each edge contour.  Discard contours less than 10 pixels long.
    [edgelist, labelededgeim] = edgelink(edgeim, 10);
    
    % Display the labeled edge image with separate colours for each
    % distinct edge (choose your favorite colourmap!)
    %figure(2), imagesc(labelededgeim); colormap(vga), axis image, axis off
    %figure(1); imshow(imo);

h = waitbar(0,'Please wait...Analysis can be time consuming for High Resolution image');  
    Nmax=max(max(labelededgeim));

    %taille memoire resultat!
SC=zeros(1000,2,100);
    for uu=1:Nmax
        waitbar(uu/Nmax,h)
        [r,c] = find(labelededgeim==uu);  
        rc = [r c];
        [sx sy]=size(rc);
        [imx,imy]=size(labelededgeim);

        n1=zeros(imx,imy); 
        for i=1:sx
            x1=rc(i,1);
            y1=rc(i,2);
            n1(x1,y1)=255;
        end % Storing the extracted image in an array

Cn1=ait_imneg(n1);
%!!!attention x et y permutation
[y,x]=find(Cn1==0);

cerne=[y,x];

delta_sq = diff(cerne).^2;
perimeter = sum(sqrt(sum(delta_sq,2)));
P(uu)=perimeter/length(cerne);
  if P(uu) > threshold
    Pu(uu)=uu;
    compt=compt+1;
    SC(1:length(cerne),:,compt)=cerne;
    disp('good');
    %perimeter/length(cerne)
metric_string = [sprintf('R %d ', compt)];%,sprintf('\n'), sprintf('P %d', P(uu))];
figure(1);hold on;plot(x,y,'g.');hold on;
text(mean(x)-5,min(y)+5,metric_string,'Color','y',...
       'FontSize',11,'FontWeight','bold');

    else
    disp('NOT A RING');
    end 
end
close(h);