function rasterme(rastersize,xclip,yclip) 
% 
% RASTERME(xclip,yclip,rastersize) imports my portrait, 

% clips it to a central (xclip x yclip) region ...

% converts it to a grey-scale image. 

% very simple, inefficient implementation. use for

% discussion of linear map, matrix representation

%

% transformed images are shown side-by-side... 
% 
% Author: Matthias Kawski, July 2001 
%         http://math.la.asu.edu/~kawski   
% 
if nargin < 1    
   rastersize=2;    
end
 


% 
% Import an image -- the standard format is .tif 
% The following is a photoshop conversion of me.jpg 
% 
portrait=imread('me.tif'); 
[M,N,R]=size(portrait)  % default: work w/ whole picture 
if nargin < 3    
   m = M;    
   n = N;
end


if nargin > 2
   
   m = xclip;
   
   n = yclip; end
; 
portrait=double(portrait)+1; % convert from uint8 to integer 
image(portrait/256)          % image wants rgb values in [0,1] 
% 
disp('Hit any key to continue') 
pause 
% 
% To get a grey image take average of RGB channels 
% The following code is awkward -- due to my lack 
% of experience three dimensional m x n x r arrays 
% 
pp=(portrait(:,:,1)+portrait(:,:,2)+portrait(:,:,3))/3/256; 
 
ppp(:,:,1)=pp; 
ppp(:,:,2)=pp; 
ppp(:,:,3)=pp; 
% image(ppp) 
% 
% clipping the image 
% 
if m > M     
   m = M; end
 
if n > N     
   n = N;    
end

 




m=rastersize*floor(m/rastersize);

n=rastersize*floor(n/rastersize);

r=rastersize;



m0=floor((M-m)/2)+1; 
n0=floor((N-n)/2)+1; 
pp=pp(m0:m0+m-1,n0:n0+n-1,:); 
ppp=zeros(m,n,3); 
ppp(:,:,1)=pp; 
ppp(:,:,2)=pp; 
ppp(:,:,3)=pp; 
image(ppp) 
% 
disp('Hit any key to continue') 
pause 
% 
qq=zeros(size(pp));

for i=[0:m/r-1]
   
   for j=[0:n/r-1]
      
      for k=[1:r]
         
         for l=[1:r]
            
            qq(r*i+k,r*j+l)=sum(sum(pp(r*i+1:r*i+r,r*j+1:r*j+r)));
            
         end
         
      end
            
   end
   
end

qq = qq/r/r;
% 
ppp(:,:,1)=pp; 
ppp(:,:,2)=pp; 
ppp(:,:,3)=pp; 

qqq(:,:,1)=qq; 
qqq(:,:,2)=qq; 
qqq(:,:,3)=qq; 

vstrip=zeros(m,1,3); 
hstrip=zeros(1,2*n+3,3); 
image([hstrip;vstrip,ppp,vstrip,qqq,vstrip;hstrip]) 
%