www.pudn.com > matsource.rar > adaptiveThres.m

function [o] = adaptiveThres(a,W,noShow); 
%Adaptive thresholding is performed by segmenting image a 
%Honors Project 2001~2002 
%wuzhili 99050056 
%comp sci HKBU 
%last update 19/April/2002 
 
[w,h] = size(a); 
o = zeros(w,h); 
 
%seperate it to W block 
%step to w with step length W 
 
for i=1:W:w 
for j=1:W:h 
mean_thres = 0; 
 
%white is ridge -> large 
 
if i+W-1 <= w & j+W-1 <= h 
   	mean_thres = mean2(a(i:i+W-1,j:j+W-1)); 
   	%threshold value is choosed 
      mean_thres = 0.8*mean_thres; 
      %before binarization 
      %ridges are black, small intensity value -> 1 (white ridge) 
      %the background and valleys are white, large intensity value -> 0(black) 
      o(i:i+W-1,j:j+W-1) = a(i:i+W-1,j:j+W-1) < mean_thres; 
end; 
    
end; 
end; 
 
 
if nargin == 2 
imagesc(o); 
colormap(gray); 
end;