Can anyone provide me with the matab code for Huffman encoding to compress an image?

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Nidhi Kumari 2018-8-26

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评论： Walter Roberson 2020-8-31

I am new to matab and have to write the code for Huffman encoding. I found many functions to apply Huffman encoding but i am not able to write the rest of the code or to use that function. So it would be very helpful if anyone can provide me the code from starting to end for image compression using Huffman encoding and for decoding too.

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hamza munawar 2020-8-31

do yo apply huffman encoding in a 2D image???

Walter Roberson 2020-8-31

You CAN apply Huffman coding to a 2d image.

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Answer 1

KALYAN ACHARJYA 2018-8-26

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Nidhi Kumari 2018-8-29

在 MATLAB Online 中打开

filename = input('enter the image file name', 's');
string = imread(filename);
string = string(:);         %input string
symbol=[];                                %initialise variables
count=[];
j=1;
%------------------------------------------loop to separate symbols and how many times they occur
for i=1:length(string)                   
flag=0;    
flag=ismember(symbol,string(i));      %symbols
    if sum(flag)==0
    symbol(j) = string(i);
    k=ismember(string,string(i));
    c=sum(k);                         %no of times it occurs  
    count(j) = c;
    j=j+1;
    end 
end    
ent=0;
total=sum(count);                         %total no of symbols
prob=[];                                         
%-----------------------------------------for loop to find probability and
%entropy
for i=1:1:size((count)');                   
prob(i)=count(i)/total;
ent=ent-prob(i)*log2(prob(i));            
end
var=0;
%-----------------------------------------function to create dictionary
[dict avglen]=huffmandict(symbol,prob);    
% print the dictionary.
       temp = dict;
       for i = 1:length(temp)
       temp{i,2} = num2str(temp{i,2});
       var=var+(length(dict{i,2})-avglen)^2;  %variance calculation
       end
       temp
%-----------------------------------------encoder  and decoder functions           
sig_encoded=huffmanenco(string,dict)
deco=huffmandeco(sig_encoded,dict);
equal = isequal(string,deco)
%-----------------------------------------decoded string and output
%variables
str ='';
for i=1:length(deco)    
str= strcat(str,deco(i));
end
disp('**str**')
str
disp('**ent**')
ent
disp('**avglen**')
avglen
disp('**var**')
var

Nidhi Kumari 2018-8-29

I want to take an image as input and save the compressed form.

Walter Roberson 2018-8-29

在 MATLAB Online 中打开

You have

sig_encoded=huffmanenco(string,dict)

The variable sig_encoded is the compressed image. It has one bit of usable information for each vector location.

You can write the compressed image to file using one bit per location, if you use fwrite() with 'bit1' conversion specification.

Note that really you should also write the dictionary to the file as well. You do not need to write the probabilities, but you do need to write the table of which bit combinations correspond to which symbol. You also need to find a way of writing into the file information about where the bit stream stops, because it is not possible to stop writing in the middle of a byte. You probably also want to write information about the image size so that you know how to rearrange the decoded bits.

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