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 function modify( path )
% output_image = modify( input_image , raw_image )
% input_image : bw image of centers 
% raw_image : raw image so that user can more easily located where centers
% should be
% output_image : bw image of centers after user has modified them
%
% method: user LEFT clicks to create a center
%   user RIGHT click to remove a center, users findnearest to remove
%   nearest center
%   user CENTER clicks to exit

load('-mat', path, 'x','y','N', 'xmax', 'ymax', 'rotim', 'conn');

figure(1) 
    imagesc(rotim)
    hold on
    plot( x, y, 'b+');
    hold off
    colormap gray
    truesize
    title 'LEFT click = create center, RIGHT click = remove center, CENTER to end or pause '
    
disp( 'to zoom or pan, first pause, then adjust while paused')
    
cont = 'y';
while cont ~= 'q'  
    figure(1)
    [xxx,yyy,button] = ginput(1);
    xxx = round(xxx);
    yyy = round(yyy); 
    
    % check for out of bounds
    if( xxx<0 | yyy<0 | xxx> xmax | yyy > ymax)
        break;
    end
    
    if button == 1
        % create a center
        x = [x;xxx];
        y = [y;yyy];
        conn = [conn;0,0,0,0,0,0];
        N = N+1;
        
        hold on
        plot(xxx,yyy,'g+')
        hold off
        
    elseif button == 3
        % remove a center
        n = findclosest(x,y, xxx,yyy );
        
        hold on
        plot(x(n),y(n),'ro')
        hold off
        
        y(n) = [];
        x(n) = [];
        
        for a = 1:6
            if conn(n,a) ~= 0
                conn(conn(n,a), mod(a+2,6)+1) = 0;
            end
        end
        conn(n, :) = [];
        % trickle down effect (now all numbers > n are wrong
        temp = [];
        for a = 1: numel(conn(:))
            if conn(a) > n
                conn(a) = conn(a) - 1;
            end
        end       
        
        N = N-1;        
    else
        cont = input( '[p]ause [q]uit: ','s');
        if cont ~= 'q'
            pause;
        end
    end
end        
    close(1)
    
    save(path, 'x','y', 'N','conn', '-mat', '-append');