arencode.m

常用图像压缩编码码matlab实现。包括：DM编码、变换编码（FFT和DCT）、算术编码、行程编码、Huffman编码、线性预测编码和一个近似的JPEG编码过程。非常适合入门用户实践。

function arcode = arencode(symbol, pr, seqin)
%算术编码
%输出：码串
%输入：symbol：字符行向量
%      pr：字符出现概率
%      seqin：待编码字符串

high_range = [];
for k = 1: length(pr),
    high_range = [high_range sum(pr(1: k))];
end

low_range = [0 high_range(1: length(pr) - 1)];
sbidx = zeros(size(seqin));
for i = 1: length(seqin),
    sbidx(i) = find(symbol == seqin(i));
end

low = 0; high = 1;
for i = 1: length(seqin),
    range = high - low;
    high = low + range * high_range(sbidx(i));
    low = low + range * low_range(sbidx(i));
end
arcode = low;