fig9_4.m

these are the Mtlab functions to plot the figures in the book Communication system (by Haykin)

%dct variance 

img=imread('flower.bmp','bmp');
imshow(img);

dctimg=blkproc(img,[8 8],'dct2');
dctmag=dctimg.^2;
[height,width]=size(img)
for (i=1:8) for (j=1:8)
      dctvar(i,j)=sum(sum(dctmag(i:8:height,j:8:width)))
   end;
end;

dctvar=dctvar/(height/8*width/8);

zigzag=[1,2,6,7,15,16,28,29;
   3,5,8,14,17,27,30,43;
   4,9,13,18,26,31,42,44;
   10,12,19,25,32,41,45,54;
   11,20,24,33,40,46,53,55;
   21,23,34,39,47,52,56,61;
   22,35,38,48,51,57,60,62;
   36,37,49,50,58,59,63,64];

for (i=1:8) for (j=1:8)
      dctvar1d(zigzag(i,j))=dctvar(i,j);
   end;
end;
dctvar1d
semilogy(dctvar1d), axis tight;
ylabel('DCT coefficient variance'); xlabel('coefficient index in zigzag order');