function B=Code_Huffman(A)
%根據huffman編碼表對量化后的數據編碼
%依次輸入DC系數差值(A中DC系數已做過差分)和AC系數的典型Huffman表
%只處理8×8DCT系數量化矩陣，每個A都是8*8
DC_Huff={'00','010','011','100','101','110','1110','11110','111110','1111110','11111110','111111110'};
%由于AC系數數據量較大，我們將它保存在AC_Huff.txt文件中，將它讀入元胞數組中
fid=fopen('AC_Huff.txt','r');
AC_Huff=cell(16,10);
for a=1:16
    for b=1:10
        temp=fscanf(fid,'%s',1);%以行為單位讀取，保存在temp中
        AC_Huff(a,b)={temp};%代表每行的一組數據
    end
end
fclose(fid);
%對A中的數據進行Zig-Zag掃描，保存在數組Z中
i=1;
for a=1:15
    if a<=8
        for b=1:a
            if mod(a,2)==1
               Z(i)=A(b,a+1-b);
               i=i+1;
            else
               Z(i)=A(a+1-b,b);
               i=i+1;
            end
            
        end
    else
        for b=1:16-a
            if mod(a,2)==0
               Z(i)=A(9-b,a+b-8);
               i=i+1;
            else
               Z(i)=A(a+b-8,9-b);
               i=i+1;
            end                              
        end
    end
end
%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
%%%先對DC差值系數編碼：前綴碼SSSS+尾碼
%dc為其Huffman編碼
if Z(1)==0
    sa.s=DC_Huff(1);   %%%size分量存放前綴碼
    sa.a='0';           %%%amp分量存放尾碼
    dc=strcat(sa.s,sa.a);
else    
    n=fix(log2(abs(Z(1))))+1;
    sa.s=DC_Huff(n);
    sa.a=binCode(Z(1));
    dc=strcat(sa.s,sa.a);
end
%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%

%%%再對AC系數進行行程編碼,保存在結構體數組rsa中
if isempty(find(Z(2:end)))  %如果63個交流系數全部為0，rsa系數全部為0
    rsa(1).r=0;             %行程runlength
    rsa(1).s=0;             %碼長size
    rsa(1).a=0;             %二進制編碼
else
   T=find(Z);              %找出Z中非零元素的下標
   T=[0 T(2:end)];         %為統一處理將第一個下標元素置為0
   i=1;                    % i為rsa結構體的下標  
   %從第二個元素即第一個交流元素開始處理
   j=2;
   while j<=length(T)
       t=fix((T(j)-1-T(j-1))/16);   %判斷下標間隔是否超過16
       if t==0                      %如果小于16，較簡單
           rsa(i).r=T(j)-T(j-1)-1;
           rsa(i).s=fix(log2(abs(Z(T(j)))))+1;
           rsa(i).a=Z(T(j));
           i=i+1;
       else                         %如果超過16，需要處理（15，0）的特殊情況
           for n=1:t                %可能出現t組（15，0） 
               rsa(i)=struct('r',15,'s',0,'a',0);
               i=i+1;
           end
           %接著處理剩余的那部分
           rsa(i).r=T(j)-1-16*t;
           rsa(i).s=fix(log2(abs(Z(T(j)))))+1;
           rsa(i).a=Z(T(j));
           i=i+1;
       end
       j=j+1;
   end
   %判斷最后一個非零元素是否為Z中最后一個元素
   if T(end)<64
       rsa(i).r=0;
       rsa(i).s=0;
       rsa(i).a=0;
   end                      %以EOB結束
end
%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
%%%%%%%%---------通過查表獲取AC系數的Huffman編碼

B=dc;                         %B初始化為直流系數編碼
for n=1:length(rsa)
    if rsa(n).r==0&rsa(n).s==0&rsa(n).a==0
        ac(n)={'1010'};  
    elseif rsa(n).r==15&rsa(n).s==0&rsa(n).a==0
        ac(n)={'11111111001'};
    else
        t1=AC_Huff(rsa(n).s+1,rsa(n).s);
        t2=binCode(rsa(n).a);
        ac(n)=strcat(t1,t2);
      
    end
   B=strcat(B,ac(n));
end    
    
    
%%%-------------Subfunction----------%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
function s=binCode(a)
%求任意整數的二進制碼
if a>=0
    s=dec2bin(a);
else
%求a的反碼，返回“01”字符串，按位取反
    s=dec2bin(abs(a));
    for t=1:numel(s)
        if s(t)=='0'
            s(t)='1';
        else s(t)='0';
        end
    end
end
%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%