icircle.m

这是一个基于MATLAB的机器视觉工具箱,里面用很多非常有价值的的程序

%ICIRCLE 	Create circular structuring element
%
%	S = ICIRCLE(R)
%	S = ICIRCLE(R, W)
%
%	Return a square matrix of zeros with a central circular region of 
%	radius R of ones.  Matrix size is (2R+1) x (2R+1) or WxW.
%
%	If R is a 2-element vector then it returns an annulus of ones, and
%	the two numbers are interpretted as inner and outer radii.
%
%
%	Copyright (c) Peter Corke, 1999  Machine Vision Toolbox for Matlab

%		pic 3/95
%
function s = icircle(r, w)

	if ismatrix(r) 
		rmax = max(r(:));
		rmin = min(r(:));
	else
		rmax = r;
	end

	if nargin == 1,
	  w = 2*rmax+1;
	  c = rmax+1;
	else
	  c = ceil(w/2);
	end
	s = zeros(w,w);

	if ismatrix(r) 
		s = circle(rmax,w) - circle(rmin, w);
	else
		[x,y] = find(s == 0);
		x = x - c;
		y = y - c;
		l = find(sqrt(x.^2+y.^2) <= r);
		s(l) = ones(length(l),1);
	end