design4x512.m

数字图像的压缩技术

function design()
%   create a codebook 
%   sig--------image signal 
%   re_sig--------reform image signal--fit to VQ
%   siz_word---the size of codeword 
%   siz_book---the size of codebook
%   m_sig------the number of image matrix row
%   n_sig------the number of image matrix column
figure(1);
sig=imread('lena.bmp');
[m_sig,n_sig]=size(sig);
siz_word=4;
siz_book=512;

if m_sig~=n_sig
   error('signal is not fitable for quantization.');
end
if mod(m_sig,siz_word)~=0
   error('signal is also not fitable for quantization.');
end
imshow(sig);
%reshape the image into a vector(siz_word*siz_word*num)
num=m_sig/siz_word;%32
ss=siz_word*siz_word;%64
nn=num*num;%1024
re_sig=[];%64,1024
for i=1:m_sig
   for j=1:m_sig
      f1=floor(i./siz_word);
      m1=mod(i,siz_word);
      if m1==0
         m1=siz_word;
         f1=f1-1;
      end
      f2=floor(j./siz_word);
      m2=mod(j,siz_word);
      if m2==0
         m2=siz_word;
         f2=f2-1;
      end
      re_sig(num*f1+f2+1,siz_word*(m1-1)+m2)=sig(i,j);
   end
end

%  Initial codevector Using random number generator
codebook=[];
for i=1:siz_book
   r=floor(rand*nn);
   codebook=[codebook;re_sig(r,:)];
end
%  LBG algorithm
sea=100;
while  sea<=0.0001
   d1=0.0;
   for i=1:siz_book
      VectorNumber(i)=0;   % the number of codeword of every class is 0
   end
   for i=1:nn
      CodeNumber(i)=1;
      min=VectorDistance(siz_word,re_sig(i,:),codebook(1,:));
      for j=2:siz_book
         d=0.0;
         for l=2:siz_word
            d=d+(re_sig(i,l)-codebook(j,l))^2;
            if d>=min 
               break;
            end
         end
         if d<min
            min=d;
            CodeNumber(i)=j;
         end
      end
      VectorNumber(CodeNumber(i))=VectorNumber(CodeNumber(i))+1;
      d1=d1+min;
   end
   sea=(d0-d1)/d1;
   if sea<=0.0001
      break;
   end
   d0=d1;
   for j=1:siz_book
      if VectorNumber[j]~=0
         dd=zeros(1,siz_word);
         for l=1:nn
            if CodeNumber(l)==j
               for k=1:siz_word
                  dd(k)=dd(k)+re_sig(l,k);
               end
            end
         end
         for k=1:siz_word
            codebook(j,k)=dd(k)/VectorNumber(j);
         end
      else
         msgbox('select a random vector');
         l=floor(rand*nn);
         codebook(j,:)=re_sig(l,:);
     end
  end
end
save codebook4_512 codebook;

function z=VectorDistance(siz_word, Vector1, Vector2)
for i=1:siz_word
   z=z+(Vector1(i)-Vector2(i))^2;
end