adaptstats

 ADAPTSTATS gets the local mean and standard deviations for each pixel in the image within a region.
 
 USAGE:
     [mimg,stdv]=adaptstats(img,win);
     [mimg,stdv]=adaptstats(img);
 
 INPUTS:
     img: grayscale image of class double
 
     win: (optional) default value is min(size(img))/5, win is the size of
     the region

0001 function [mimg,stdv]=adaptstats(img,win)
0002 % ADAPTSTATS gets the local mean and standard deviations for each pixel in the image within a region.
0003 %
0004 % USAGE:
0005 %     [mimg,stdv]=adaptstats(img,win);
0006 %     [mimg,stdv]=adaptstats(img);
0007 %
0008 % INPUTS:
0009 %     img: grayscale image of class double
0010 %
0011 %     win: (optional) default value is min(size(img))/5, win is the size of
0012 %     the region
0013 
0014 %Check input
0015 if ~exist('win','var') || isempty(win)
0016     % default win size
0017     win=round(min(size(img))/5);
0018 end
0019 
0020 % create integral image, integral image allows for quicker execution time
0021 % for large window sizes.
0022 intimg = cumsum(cumsum(img),2);
0023 intimg2 = cumsum(cumsum(img.^2),2);
0024 
0025 hwin=floor(win/2);
0026 
0027 % pad integral images
0028 
0029 intimg=padarray(intimg,[hwin+1,hwin+1],'pre');
0030 intimg=padarray(intimg,[hwin,hwin],'post','replicate');
0031 intimg2=padarray(intimg2,[hwin+1,hwin+1],'pre');
0032 intimg2=padarray(intimg2,[hwin,hwin],'post','replicate');
0033 
0034 % get mean and stdv images
0035 simg=intimg(1:size(img,1),1:size(img,2))+intimg(win+1:size(img,1)+win,win+1:size(img,2)+win)...
0036     -intimg(1:size(img,1),win+1:size(img,2)+win)-intimg(win+1:size(img,1)+win,1:size(img,2));
0037 simg2=intimg2(1:size(img,1),1:size(img,2))+intimg2(win+1:size(img,1)+win,win+1:size(img,2)+win)...
0038     -intimg2(1:size(img,1),win+1:size(img,2)+win)-intimg2(win+1:size(img,1)+win,1:size(img,2));
0039 
0040 n=win^2;
0041 mimg=simg/n;
0042 vari=(simg2-(mimg.^2)*n)/(n-1);
0043 stdv=sqrt(vari);