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## Non-Local Means Filter

version 1.0 (2.22 KB) by

Non-Local Means Filter for image denoising

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Updated

Implementation of the Non-Local Means Filter proposed by Buades et al. for robust image denoising.

typical usage:

fima=nlmeans(ima,5,2,sigma);

being sigma the noise standard deviation

zheng f

Nina

### Nina (view profile)

d = sum(sum(kernel.*(W1-W2).*(W1-W2)));
w=exp(-d/h); % the h was replaced by h*h in the line32

Aman Sharma

### Aman Sharma (view profile)

d = sum(sum(kernel.*(W1-W2).*(W1-W2)));
This line throws an error.
"Error using ==> times
Integers can only be combined with integers of the same class, or scalar doubles."
How do we rectify that?

lynnea lin

### lynnea lin (view profile)

I doubt if it should be
d = sqrt(sum(sum(kernel.*(W1-W2).*(W1-W2))));
w=exp(-d/(h*h));
not
d = sum(sum(kernel.*(W1-W2).*(W1-W2)));
w=exp(-d/h);
??

521

Micaela Gonzales

chao zhang

### chao zhang (view profile)

I have a great hope to download the code justnow, i wish it will give me great help!

chao zhang

Jing Hu

### Jing Hu (view profile)

Javier Agustin Romero

### Javier Agustin Romero (view profile)

Thanks for the contribution, Jose.

li teng

Tarun Katyal

### Tarun Katyal (view profile)

for i=1:m
for j=1:n

i1 = i+ f;
j1 = j+ f;

W1= input2(i1-f:i1+f , j1-f:j1+f);

wmax=0;
average=0;
sweight=0;

rmin = max(i1-t,f+1);
rmax = min(i1+t,m+f);
smin = max(j1-t,f+1);
smax = min(j1+t,n+f);

for r=rmin:1:rmax
for s=smin:1:smax

if(r==i1 && s==j1) continue; end;

W2= input2(r-f:r+f , s-f:s+f);

could someone explain how are these W1 and W2 points calculated??
plz help not able to understand the code

John

### John (view profile)

I believe there is a bug in this code. If you change the line in demo.m, to display the error between the filtered and original images, i.e. from:

subplot(2,2,4),imagesc(rima-fima),title('residuals');

to

subplot(2,2,4),imagesc(ima-fima),title('residuals');

There is a clear bias/issue with the lower left hand quadrant edges, but not with the upper right hand quadrant edges.

Vikram Venkatraghavan

selma

### selma (view profile)

thanks for helping us

Prabhakar

### Prabhakar (view profile)

Suggest me how to give external image by applying this code

max(a,b)
what is the return type its array or int value i am getting trouble when i am implementing in java

Zhang Xuande

cool!!

YoonOh Tak

### YoonOh Tak (view profile)

Is this line right?

fima=NLmeansfilter(ima,5,2,sigma);

I think it has to change like below

fima=NLmeansfilter(rima,5,2,sigma);

priyanka reddy

### priyanka reddy (view profile)

i have the same doubt what crisitna asked. can you help me. can u send me the modified codings

Royi Avital

### Royi Avital (view profile)

Hello.
You mention to have the "Original" version which is slower yet easier to understand,
Where can I find it?
Thanks.

Tai Fei

### Tai Fei (view profile)

Hi, Jose, I have 2 questions on the kernel.
1). Is it gaussian kernel which is mentioned in the paper of Buades. As far as i know, the one in your code is not gaussian.
2). why you take these two steps ?
average = average + wmax*input2(i1,j1);
sweight = sweight + wmax;

I cannot find any ground in the original paper, but it does make my algorithm oscillate less. could you give me some idea, why you make them ?

Victor Lee

### Victor Lee (view profile)

Hi Jose, you've mention of the bug earlier on but I can't seem to find it. Is it rectified and updated?

Abhishek Bansal

### Abhishek Bansal (view profile)

how to calculate sigma, h and f? I am confused. I am a student, need urgent help. u can also email me at abhishek85bansal@gmail.com

Haoheng Zheng

### Haoheng Zheng (view profile)

Good, but few notation...

Vijay

### Vijay (view profile)

Performance of the algorithm will depend on the sigma estimation in noisy image. How to estimate good sigma?

cristina

### cristina (view profile)

I must define input,f,t,h...I'm not sure that I know how!
Can you help me please?I'm a beginer in matlab...thank you!

cristina

### cristina (view profile)

I have a little error here [m n]=size(input); in NLmeansfilter.m:

> NLmeansfilter
??? Input argument 'input' is undefined.

Error in ==> C:\Documents and Settings\Iulia\Desktop\matlab\NLmeansfilter.m
On line 19 ==> [m n]=size(input);

I need help...Thanks!

Jose Manjon

You are right Bi Yiming.

Jose

Bi Yiming

i think it should be
fima=NLmeansfilter(rima,5,2,sigma);
not fima=NLmeansfilter(ima,5,2,sigma);
in demo.m

Kevin Verghese

d = sum(sum(kernel.*(W1-W2).*(W1-W2)));
This line throws an error.
"Error using ==> times
Integers can only be combined with integers of the same class, or scalar doubles."
How do we rectify that?

Jose Manjon

You have to use sigma, not 10*sigma

being signa the image noise standard deviation

Jose

Roger Ting

How to set the sigma for the algorithm.I chose 10*noisesigma, the result is very bad.

Good Work,

Only, please change the word "radio" to "size" (in the definitions of "t" and "f")

Thanks

victor diaz

Jose Manjon

The original code was not optimized to easily understand the filter caracteristics. Now, I have already vectorized it to speed up the filter. New version is much faster but if you plan to use it rutinarily I suggest you to mex it.

Peter L

It is really slow. You need to vectorize it.

Jose Manjon

There is a small bug in the code, please
chage:

k=max(abs(i),abs(j));

for

k=max([abs(i),abs(j),1]);

enjoy the filter

Jose Manjon

James Chan

cool