?? jdcenc.m
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function b=jdcenc(x)% Usage: b=jdcenc(x)% Hoffman encoding of DC coefficients in JPEG% copyright(c) 1997 by Yu Hen Hu%% category c = floor(log2(abs(x)))+1% append code is the binary representation of abs(x) if x>0% of the 1's complement of bianry rep of abs(x) if x < 0% created: 11/25/97% first figure out category numberif x ==0, %b=[0 1 0]; b=[0 0]; return % doneelse c = floor(log2(abs(x)))+1;end% Hoffman tabletbl=[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 2 0 0 0 0 0 0 0 0 0 3 1 0 1 0 0 0 0 0 0 5 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]; % This table is in the pdf file, print out taken % Modified 27 sept 2003, 2325 Hrs tab=[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]; tbl=tab; % This is changed by Ravi Lakkundib=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?? 快捷鍵說明
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