%jpeg直流系數HUFFMAN編碼function b = dcencode(x)% x == 0 的特殊情況編碼if x == 0   b = [0 0];   return else   %數值范圍分類   c = floor(log2(abs(x)))+1;end% Hoffman tabletbl = [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]; b = tbl(c+1,2:tbl(c+1,1)+1);tmp=int2bin(x,c);  % tmp is 1 by c+1 vector containing sign-mag% representation of x, first bit is sign bit.if tmp(1)==0, % if x > 0   b=[b tmp(2:c+1)];elseif tmp(1)==1, % if x < 0   b=[b ones(1,c)-tmp(2:c+1)];end