www.pudn.com > huffman.rar > huffman_demo2.m

function huffman_demo2 
%HUFFMAN_DEMO2 
%   This demo shows compression-decompression of different data. 
 
%   $Author: Giuseppe Ridino' $ 
%   $Revision: 1.0 $  $Date: 02-Jul-2004 16:47:25 $ 
 
 
fprintf('\n') 
disp('This is an example of function using Huffman compression-decompression') 
disp('Press a key to continue...') 
pause 
fprintf('\n') 
 
fprintf('\n') 
disp('The string below will be compressed and decompressed') 
disp('using norm2huff and huff2norm functions') 
disp('Press a key to continue...') 
pause 
fprintf('\n') 
 
data1 = 'This is a string demo. It will be compressed using norm2huff function.' 
 
fprintf('\n') 
disp('Now we will compress and decompress it.') 
disp('But pay attention that data mut be converted to uint8!') 
disp('Press a key to continue...') 
pause 
fprintf('\n') 
 
% string data 
data1 = uint8(data1); 
[zipped1,info1] = norm2huff(data1) 
unzipped1 = char(huff2norm(zipped1,info1)) 
 
isOK = isequal(data1,unzipped1) 
 
whos data1 zipped1 unzipped1 
 
bar(frequency(data1)); axis tight 
 
%  random data1 
fprintf('\n') 
disp('Now we will try to compress a random sequence of 1000 bytes') 
disp('Press a key to continue...') 
pause 
fprintf('\n') 
 
data3 = uint8(256*rand(1,1000)); 
[zipped3,info3] = norm2huff(data3); 
unzipped3 = huff2norm(zipped3,info3); 
 
isOK = isequal(data3,unzipped3) 
 
whos data3 zipped3 unzipped3 
 
bar(frequency(data3)); axis tight 
 
fprintf('\n') 
disp('It is not well compressed. Why?') 
disp('This is because the sequence is normally random!') 
disp('Press a key to continue...') 
pause 
fprintf('\n') 
 
%  random data2 
fprintf('\n') 
disp('Now we will try to compress a random sequence of 1000 bytes but not normally distributed') 
disp('Press a key to continue...') 
pause 
fprintf('\n') 
 
data4 = uint8(256*rand(1,1000).^3); 
[zipped4,info4] = norm2huff(data4); 
unzipped4 = huff2norm(zipped4,info4); 
 
isOK = isequal(data4,unzipped4) 
 
whos data4 zipped4 unzipped4 
 
bar(frequency(data4)); axis tight 
 
fprintf('\n') 
disp('As the distribution is not uniform, the compression ratio is a bit more significant') 
disp('Press a key to continue...') 
pause 
fprintf('\n') 
 
% TERMINATED 
fprintf('\n') 
disp('#### FINISH ####')