压缩解压

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Matlab

huffencode.m：源码内容

							%huffencode函数对输入矩阵vector进行Huffman编码，返回编码后的向量（压缩后数据）及相关信息
function [zipped,info]=huffencode(vector)
if~isa(vector,'uint8')
    eror('input argument must be a uint8 vector');
end
[m,n]=size(vector);
vector=vector(:)';
f=frequency(vector);
symbols=find(f~=0);
f=f(symbols);
[f,sortindex]=sort(f);
symbols=symbols(sortindex);
len=length(symbols);
symbols_index=num2cell(1: len);
codeword_tmp=cell(len,1);
while length(f)>1
    index1=symbols_index{1};
    index2=symbols_index{2};
    codeword_tem(index1)=addnode(codeword_tem(index1),uint8(0));
    codeword_tem(index2)=addnode(codeword_tem(index2),uint8(1));
    f=[sum(f(1: 2))f(3: end)];
    symbols_index=[{[index1,index2]} symbols_index(3: end)];
    [f,sortindex]=sort(f);
    symbols_index=symbols_index(sortindex);
end
codeword=cell(256,1);
codeword(symbols)=codeword_tmp;
len=0;
for index=1:length(vector)
    len=len+length(codeword{double(vector(index))+1});
end
string=repmat(uint8(0),1,len);
pointer=1;
for index=1:length(vector)
    code=codeword{double(vector(index))+1};
    len=length(code);
    string(pointer+(0:len-1))=code;
    pointer=pointer+len;
end
len=length(string);
pad=8-mod(len,8);
if pad>0
    string=[string uint8(zeros(1,pad))];
end
codeword=codeword(symbols);
codelen=zeros(size(codeword));
weights=2.^(0:23);
maxcodelen=0;
for index=1:length(codeword)
    len=length(codeword{index});
    if len>maxcodelen
        maxcodelen=len;
    end
    if len>0
        code=sum(weights(codeword{index}==1));
        code=bitset(code,len+1);
        codeword{index}=code;
        codelen(index)=len;
    end
end
codeword=[codeword{:}];
cols=length(string)/8;
string=reshape(string,8,cols);
weights=2.^(0:7);
zipped=uint8(weights*double(string));
huffcodes=sparse(1,1);
for index=1:nnz(codeword)
    huffcodes(codeword(index),1)=symbols(index);
end
info.pad=pad;
info.huffcodes=huffcodes;
info.ratio=cols./length(vector);
info.length=length(vector);
info.maxcodelen=maxcodelen;
info.rows=m;
info.cols=n;

						