function y = imgrayslice(x, xa, xb, yo) L = 256; if nargin == 1, xa = 3*L/8-1; xb = 5*L/8-1; yo = 13*L/16-1; elseif nargin < 4 return end y = zeros(size(x)); x = double(x); % I k = x<=xa; y(k) = x(k); % II k = (x>xa)&(x<=xb); y(k) = yo; % III k = (x>xb); y(k) = x(k);