matlab图像专题;10 DCT变换对灰度图像压缩案例程序.zip

function varargout = Huff06(xC, ArgLevel, ArgSpeed) % Huff06 Huffman encoder/decoder with (or without) recursive splitting % Vectors of integers are Huffman encoded, % these vectors are collected in a cell array, xC. % If first argument is a cell array the function do encoding, % else decoding is done. % % [y, Res] = Huff06(xC, Level, Speed); % encoding % y = Huff06(xC); % encoding % xC = Huff06(y); % decoding % ------------------------------------------------------------------ % Arguments: % y a column vector of non-negative integers (bytes) representing % the code, 0 <= y(i) <= 255. % Res a matrix that sum up the results, size is (NumOfX+1)x4 % one line for each of the input sequences, the columns are % Res(:,1) - number of elements in the sequence % Res(:,2) - zero-order entropy of the sequence % Res(:,3) - bits needed to code the sequence % Res(:,4) - bit rate for the sequence, Res(:,3)/Res(:,1) % Then the last line is total (which include bits needed to store NumOfX) % xC a cell array of column vectors of integers representing the % symbol sequences. (should not be to large integers) % If only one sequence is to be coded, we must make the cell array % like: xC=cell(2,1); xC{1}=x; % where x is the sequence % Level How many levels of splitting that is allowed, legal values 1-8 % If Level=1, no further splitting of the sequences will be done % and there will be no recursive splitting. % Speed For complete coding set Speed to 0. Set Speed to 1 to cheat % during encoding, y will then be a sequence of zeros only, % but it will be of correct length and the other output % arguments will be correct. % ------------------------------------------------------------------ % SOME NOTES ON THE FUNCTION % huff06 depends on other functions for Huffman code, and the functions in this file % HuffLen - find length of codewords (HL) % HuffTabLen - find bits needed to store Huffman table information (HL) % HuffCode - find huffman codewords % HuffTree - find huffman tree %---------------------------------------------------------------------- % Copyright (c) 1999-2000. Karl Skretting. All rights reserved. % Hogskolen in Stavanger (Stavanger University), Signal Processing Group % Mail: karl.skretting@tn.his.no Homepage: http://www.ux.his.no/~karlsk/ % % HISTORY: % Ver. 1.0 13.06.2000 KS: Function made based on huff04 % Ver. 1.1 20.06.2000 KS: Handle some more exceptions % Ver. 1.2 21.06.2000 KS: Handle also negative values % Ver. 1.3 23.06.2000 KS: Use logarithms for some sequences (line 114) % Ver. 1.4 31.07.2000 KS: If a sequence has many zeros, Run + Value coding % is done. (from line 255 and some more) % Ver. 1.5 02.08.2000 KS: May have larger integers in PutVLIC and GetVLIC % Ver. 1.6 18.01.2001 KS: MaxL in line 218 was reduced from 2^16 to 50000. % For some sequences we may have length of code word larger than 16, even % if probability was larger than 2^(-16). Ex: Hi=[12798,14241,7126,7159,3520,... % 3512,1857,1799,1089,1092,681,680,424,431,320,304,201,204,115,118,77,83,45,... % 40,24,26,18,14,4,12,3,3,4,2,2,0,1]', sum(Hi)=58029 % Ver. 1.7 21.08.2001 KS: MaxL in line 218 and 420 must be the same % We may now have long code words (also see HuffTabLen.m) %---------------------------------------------------------------------- global y Byte BitPos Speed Level Mfile='Huff06'; Debug=0; % note Debug is defined in EncodeVector and DecodeVector too % check input and output arguments, and assign values to arguments if (nargin < 1); error([Mfile,': function must have input arguments, see help.']); end if (nargout < 1); error([Mfile,': function must have output arguments, see help.']); end if (~iscell(xC)) Encode=0;Decode=1; y=xC(:); % first argument is y else Encode=1;Decode=0; if (nargin < 3); Speed=0; else Speed=ArgSpeed; end; if (nargin < 2); Level=8; else Level=ArgLevel; end; if ((length(Speed(:))~=1)); error([Mfile,': Speed argument is not scalar, see help.']); end if Speed; Speed=1; end; if ((length(Level(:))~=1)); error([Mfile,': Level argument is not scalar, see help.']); end Level=floor(Level); if (Level < 1); Level=1; end; if (Level > 8); Level=8; end; NumOfX = length(xC); end if Encode Res=zeros(NumOfX,4); % initalize the global variables y=zeros(10,1); % put some zeros into y initially Byte=0;BitPos=1; % ready to write into first position % start encoding, first write VLIC to give number of sequences PutVLIC(NumOfX); if Debug disp([Mfile,' (Encode): Level=',int2str(Level),' Speed=',int2str(Speed),... ' NumOfX=',int2str(NumOfX)]); end % now encode each sequence continuously Ltot=0; for num=1:NumOfX x=xC{num}; x=full(x(:)); % make sure x is a non-sparse column vector L=length(x);Ltot=Ltot+L; y=[y(1:Byte);zeros(50+2*L,1)]; % make more space available in y % now find some info about x to better code it maxx=max(x); minx=min(x); if (minx<0) Negative=1; else Negative=0; end if ( (((maxx*4)>L) | (maxx>1023)) & (L>1) & (maxx>minx)) % the test for LogCode could be better, I think, (ver. 1.3) LogCode=1; % this could be 0 if LogCode is not wanted else LogCode=0; end PutBit(LogCode); PutBit(Negative); I=find(x); % non-zero entries in x Sg=(sign(x(I))+1)/2; % the signs may be needed later, 0/1 x=abs(x); if LogCode xa=x; % additional bits x(I)=floor(log2(x(I))); xa(I)=xa(I)-2.^x(I); x(I)=x(I)+1; end [bits, ent]=EncodeVector(x); % store the (abs and/or log) values if Negative % store the signs for i=1:length(Sg); PutBit(Sg(i)); end; bits=bits+length(Sg); ent=ent+length(Sg)/L; end if LogCode % store the additional bits for i=1:L for ii=(x(i)-1):(-1):1 PutBit(bitget(xa(i),ii)); end end bits=bits+sum(x)-length(I); ent=ent+(sum(x)-length(I))/L; end if L>0; Res(num,1)=L; else Res(num,1)=1; end; Res(num,2)=ent; Res(num,3)=bits; end y=y(1:Byte); varargout(1) = {y}; if (nargout >= 2) % now calculate results for the total if Ltot<1; Ltot=1; end; % we do not want Ltot to be zero Res(NumOfX+1,3)=Byte*8; Res(NumOfX+1,1)=Ltot; Res(NumOfX+1,2)=sum(Res(1:NumOfX,1).*Res(1:NumOfX,2))/Ltot; Res(:,4)=Res(:,3)./Res(:,1); varargout(2) = {Res}; end end if Decode % initalize the global variables, y is set earlier Byte=0;BitPos=1; % ready to read from first position NumOfX=GetVLIC; % first read number of sequences if Debug disp([Mfile,'(Decode): NumOfX=',int2str(NumOfX),' length(y)=',int2str(length(y))]); end xC=cell(NumOfX,1); for num=1:NumOfX LogCode=GetBit; Negative=GetBit; x=DecodeVector; % get the (abs and/or log) values L=length(x); I=find(x); if Negative Sg=zeros(size(I)); for i=1:length(I); Sg(i)=GetBit; end; % and the signs (0/1) Sg=Sg*2-1; % (-1/1) else Sg=ones(size(I)); end if LogCode % read additional bits too