canny.rar_canny _边缘 canny

% CANNY - Canny edge detection % % Function to perform Canny edge detection. Code uses modifications as % suggested by Fleck (IEEE PAMI No. 3, Vol. 14. March 1992. pp 337-345) % % Usage: [gradient or] = canny(im, sigma) % % Arguments: im - image to be procesed % sigma - standard deviation of Gaussian smoothing filter % (typically 1) % % Returns: gradient - edge strength image (gradient amplitude) % or - orientation image (in degrees 0-180, positive % anti-clockwise) % % See also: NONMAXSUP, HYSTHRESH % Copyright (c) 1999-2003 Peter Kovesi % School of Computer Science & Software Engineering % The University of Western Australia % http://www.csse.uwa.edu.au/ % % Permission is hereby granted, free of charge, to any person obtaining a copy % of this software and associated documentation files (the "Software"), to deal % in the Software without restriction, subject to the following conditions: % % The above copyright notice and this permission notice shall be included in all % copies or substantial portions of the Software. % % The Software is provided "as is", without warranty of any kind. % April 1999 Original version % January 2003 Error in calculation of d2 corrected function [gradient, or] = canny(im, sigma) [rows, cols] = size(im); im = double(im); % Ensure double hsize = [6*sigma+1, 6*sigma+1]; % The filter size. gaussian = fspecial('gaussian',hsize,sigma); im = filter2(gaussian,im); % Smoothed image. h = [ im(:,2:cols) zeros(rows,1) ] - [ zeros(rows,1) im(:,1:cols-1) ]; v = [ im(2:rows,:); zeros(1,cols) ] - [ zeros(1,cols); im(1:rows-1,:) ]; d1 = [ im(2:rows,2:cols) zeros(rows-1,1); zeros(1,cols) ] - ... [ zeros(1,cols); zeros(rows-1,1) im(1:rows-1,1:cols-1) ]; d2 = [ zeros(1,cols); im(1:rows-1,2:cols) zeros(rows-1,1); ] - ... [ zeros(rows-1,1) im(2:rows,1:cols-1); zeros(1,cols) ]; X = h + (d1 + d2)/2.0; Y = v + (d1 - d2)/2.0; gradient = sqrt(X.*X + Y.*Y); % Gradient amplitude. or = atan2(-Y, X); % Angles -pi to + pi. neg = or<0; % Map angles to 0-pi. or = or.*~neg + (or+pi).*neg; or = or*180/pi; % Convert to degrees.