matlab图像压缩编码.rar

function [zipped, info] = huffencode(vector) % 输入和输出都是 uint8 格式 % info 返回解码需要的结构信息 % info.pad 是添加的比特数 % info.huffcodes 是 Huffman 码字 % info.rows 是原始图像行数 % info.cols 是原始图像列数 % info.length 是原始图像数据长度 % info.maxcodelen 是最大码长 if ~isa(vector, 'uint8') error('input argument must be a uint8 vector'); end [m, n] = size(vector); vector = vector(:)'; f = frequency(vector); %计算各符号出现的概率 symbols = find(f~=0); f = f(symbols); [f, sortindex] = sort(f); %将符号按照出现的概率大小排列 symbols = symbols(sortindex); len = length(symbols); symbols_index = num2cell(1:len); codeword_tmp = cell(len, 1); % 生成 Huffman 树，得到码字编码表 while length(f)>1 index1 = symbols_index{1}; index2 = symbols_index{2}; codeword_tmp(index1) = addnode(codeword_tmp(index1), uint8(0)); codeword_tmp(index2) = addnode(codeword_tmp(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) %得到整个图像所有比特数 len = len + length(codeword{double(vector(index))+1}); end string = repmat(uint8(0), 1, len); pointer = 1; for index = 1:length(vector) %对输入图像进行编码 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{:}]; %计算压缩的向量 cols = length(string)/8; string = reshape(string, 8, cols); weights = 2.^(0: 7); zipped = uint8(weights * double(string)); %码表存储到一个希疏矩阵 huffcodes = sparse(1, 1); for index = 1:nnz(codeword) % length(codeword) %numel(codeword) huffcodes(codeword(index), 1) = symbols(index); end %填写解码时所需的结构信息 info.pad = pad; info.huffcodes = huffcodes; info.ratio = cols./length(vector); info.length = length(vector); info.maxcodelen = maxcodelen; info.rows = m; info.cols = n; %函数addnode添加节点 function codeword_new = addnode(codeword_old, item) codeword_new = cell(size(codeword_old)); for index = 1:length(codeword_old) codeword_new{index} = [item codeword_old{index}]; end %函数frequency计算各符号出现的概率 function f = frequency(vector) if ~isa(vector, 'uint8') error('input argument must be a uint8 vector'); end f = repmat(0, 1, 256); len = length(vector); for index = 0:255 f(index+1) = sum(vector == uint8(index)); end f = f./len; %归一化