MATLAB: Huffman encoding for image

huffman codeimage

for the code-
A=imread('xyz.jpg');
A1=rgb2gray(A);
A = A1(:);
[symbols,p]=hist(A,double(unique(A)))
p=p/sum(p)
symbols=symbols/sum(symbols)
[dict,avglen]=huffmandict(symbols,p)
comp=huffmanenco(A,dict)
i am getting error-
Error using huffmandict (line 164)
Source symbols repeat
Error in new (line 7)
[dict,avglen]=huffmandict(symbols,p)
suggest necessary changes

Best Answer

I haven't used huffmandict before, but based on the document and the error message you have, I suspect your inputs are wrong.
https://www.mathworks.com/help/comm/ref/huffmandict.html
Double check your inputs to huffmandict. Make sure symbols are unique values, and p are the probability of each value. That means:
[symbols, p] = hist(A,double(unique(A)))  should be
[p, symbols] = hist(A,double(unique(A)))  because the 1st output of hist is the frequency (probability)
                                          and the second output is the unique bin (unique symbol)
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