%函數VQ.m: 向量量化%
function [O_data,bit]=VQ(I_data,I_codebook)
%O_data:經向量量化壓縮后輸出數據%
%I_data:輸入數據%
%I_codebook:向量量化碼本%
%bit:向量量化所需總位數%

[row,col]=size(I_data);
[nc,nd]=size(I_codebook);
bit_index=ceil(log2(nc));
bit=0;
sqrt_nd=sqrt(nd);
y_ratio=row/sqrt_nd;
x_ratio=col/sqrt_nd;

%將每一個向量均拿來做向量量化%
for i=1:y_ratio
   for j=1:x_ratio
      
      %取一個圖像區塊當做輸入測試向量%
      I_block=I_data((i-1)*sqrt_nd+1:i*sqrt_nd,...
         (j-1)*sqrt_nd+1:j*sqrt_nd);
      
      %尋找碼本中和此輸入向量最接近的碼本%
      distortion=sum((((ones(nc,1)*I_block(:)')-I_codebook).^2)')';
      min_distortion=min(find(distortion==min(distortion)));
      
      %將此碼字直接取代輸入向量，當做輸出向量%
      R_block=reshape(I_codebook(min_distortion,:),sqrt_nd,sqrt_nd);
      O_data((i-1)*sqrt_nd+1:i*sqrt_nd,...
         (j-1)*sqrt_nd+1:j*sqrt_nd)=R_block;
      bit=bit+bit_index;                %累加處理每一個向量的位數
   end
end