www.pudn.com > iriscode.zip > findcircle.m

% findcircle - returns the coordinates of a circle in an image using the Hough transform 
% and Canny edge detection to create the edge map. 
% 
% Usage:  
% [row, col, r] = findcircle(image,lradius,uradius,scaling, sigma, hithres, lowthres, vert, horz) 
% 
% Arguments: 
%	image		    - the image in which to find circles 
%	lradius		    - lower radius to search for 
%	uradius		    - upper radius to search for 
%	scaling		    - scaling factor for speeding up the 
%			          Hough transform 
%	sigma		    - amount of Gaussian smoothing to 
%			          apply for creating edge map. 
%	hithres		    - threshold for creating edge map 
%	lowthres	    - threshold for connected edges 
%	vert		    - vertical edge contribution (0-1) 
%	horz		    - horizontal edge contribution (0-1) 
%	 
% Output: 
%	circleiris	    - centre coordinates and radius 
%			          of the detected iris boundary 
%	circlepupil	    - centre coordinates and radius 
%			          of the detected pupil boundary 
%	imagewithnoise	- original eye image, but with 
%			          location of noise marked with 
%			          NaN values 
% 
% Author:  
% Libor Masek 
% masekl01@csse.uwa.edu.au 
% School of Computer Science & Software Engineering 
% The University of Western Australia 
% November 2003 
 
function [row, col, r] = findcircle(image,lradius,uradius,scaling, sigma, hithres, lowthres, vert, horz) 
 
lradsc = round(lradius*scaling); 
uradsc = round(uradius*scaling); 
rd = round(uradius*scaling - lradius*scaling); 
 
% generate the edge image 
[I2 or] = canny(image, sigma, scaling, vert, horz); 
I3 = adjgamma(I2, 1.9); 
I4 = nonmaxsup(I3, or, 1.5); 
edgeimage = hysthresh(I4, hithres, lowthres); 
 
% perform the circular Hough transform 
h = houghcircle(edgeimage, lradsc, uradsc); 
 
maxtotal = 0; 
 
% find the maximum in the Hough space, and hence 
% the parameters of the circle 
for i=1:rd 
     
    layer = h(:,:,i); 
    [maxlayer] = max(max(layer)); 
     
     
    if maxlayer > maxtotal 
         
        maxtotal = maxlayer; 
         
         
        r = int32((lradsc+i) / scaling); 
         
        [row,col] = ( find(layer == maxlayer) ); 
         
         
        row = int32(row(1) / scaling); % returns only first max value 
        col = int32(col(1) / scaling);     
         
    end    
     
end