%jpeg直流系數HUFFMAN編碼function b = dcencode(x)% x == 0 的情況不查表編碼if x == 0   b = [0 0];   return else   %數值范圍分類   c = floor(log2(abs(x)))+1;end% Hoffman table%   碼長 編碼tbl = [2 0 0 0 0 0 0 0 0 0       3 0 1 0 0 0 0 0 0 0       3 0 1 1 0 0 0 0 0 0       3 1 0 0 0 0 0 0 0 0       3 1 0 1 0 0 0 0 0 0       3 1 1 0 0 0 0 0 0 0       4 1 1 1 0 0 0 0 0 0       5 1 1 1 1 0 0 0 0 0       6 1 1 1 1 1 0 0 0 0       7 1 1 1 1 1 1 0 0 0       8 1 1 1 1 1 1 1 0 0       9 1 1 1 1 1 1 1 1 0];%前綴碼查表獲得 b = tbl( c+1 ,2:tbl(c+1,1)+1 );%將輸入值轉換成二進制數作為尾碼tmp = x_int2bin(x);%確定輸出原碼還是補碼if x > 0    b = [ b tmp(1:c) ];elseif x < 0   b = [ b ones(1,c)-tmp(1:c) ];end