function DCH = DC_Huffman(Z,last_Z,n);
%亮度碼字
T1 = {'00' '010' '011' '100' '101' '110' '1110' '11110' '111110' '1111110' '11111110' '111111110'};
%色度碼字
T2 = {'00' '01' '10' '110' '1110' '11110' '111110' '1111110' '11111110' '111111110' '1111111110' '11111111110'};
DIFF = Z-last_Z;
if DIFF == 0 
    SSSS = 0;
elseif (abs(DIFF) == 1) 
    SSSS = 1;
elseif (abs(DIFF) >= 2 && abs(DIFF)<=3) 
    SSSS = 2;
elseif (abs(DIFF) >= 4 && abs(DIFF)<=7) 
    SSSS = 3;
elseif (abs(DIFF) >= 8 && abs(DIFF)<=15) 
    SSSS = 4;
elseif (abs(DIFF) >= 16 && abs(DIFF)<=31) 
    SSSS = 5;
elseif (abs(DIFF) >= 32 && abs(DIFF)<=63) 
    SSSS = 6;
elseif (abs(DIFF) >= 64 && abs(DIFF)<=127) 
    SSSS = 7;
elseif (abs(DIFF) >= 128 && abs(DIFF)<=255) 
    SSSS = 8;
elseif (abs(DIFF) >= 256 && abs(DIFF)<=511) 
    SSSS = 9;
elseif (abs(DIFF) >= 512 && abs(DIFF)<=1023) 
    SSSS = 10;
elseif (abs(DIFF) >= 1024 && abs(DIFF)<=2047) 
    SSSS = 11;
end
%前綴碼
if n
S1 = char(T1(SSSS+1));
%后綴碼
if DIFF >= 0 
    S2 = dec2bin(DIFF);
else
    S2 = dec2bin(DIFF);
    for i = 1:length(S2)
        if S2(i) == '0';
            S2(i) = '1';
        else
            S(2) = '0';
        end
    end
end
DCH = [S1 S2];