huffman encoding for image

21 vues (au cours des 30 derniers jours)
Nidhi Kumari
Nidhi Kumari le 9 Oct 2018
Commenté : Walter Roberson le 26 Oct 2018
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
  3 commentaires
Nidhi Kumari
Nidhi Kumari le 10 Oct 2018
But how to make them same?
KALYAN ACHARJYA
KALYAN ACHARJYA le 10 Oct 2018
@Nidhi
I have updated the answer, please check here

Connectez-vous pour commenter.

Réponse acceptée

OCDER
OCDER le 10 Oct 2018
I haven't used huffmandict before, but based on the document and the error message you have, I suspect your inputs are wrong.
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)
  30 commentaires
Walter Roberson
Walter Roberson le 26 Oct 2018
You are using a version of MATLAB no later than R2017b: I can tell because is_a_valid_code was removed from huffmandeco as of R2018a.
Looking at the amount of memory you have, I suspect you are running R2015b or earlier with a 32 bit MATLAB.
When I test with peppers.png on R2017b on my system, the decoding took about 53 seconds.
Walter Roberson
Walter Roberson le 26 Oct 2018
I have a memory of having reported an inefficiency to MATLAB having to do with is_a_valid_code, that it was being called far too often. However, I do not seem to find that in my case list, so perhaps I reported it years ago on a different license.
Anyhow: upgrading to R2018a or later would probably speed up quite a bit.

Connectez-vous pour commenter.

Plus de réponses (0)

Catégories

En savoir plus sur Denoising and Compression dans Help Center et File Exchange

Community Treasure Hunt

Find the treasures in MATLAB Central and discover how the community can help you!

Start Hunting!

Translated by