vector median filter

is there any function in matlab for vector median filter or vector directional filter? plz help.

[Walter Roberson]

Is there a difference between "vector median filter" and "median filter applied to a vector" ?

[Yogesh Joshi]

yes, vector median filter is used for color image enhancement.

Answer 1

[Chandra Kurniawan]

for 1D median filtering, Matlab has command medfilt1

Eq:

medfilt1([4 3 5 2 8 9 1],3)
ans =
     3     4     3     5     8     8     1

[Yogesh Joshi]

actually i want to use median filter for color image enhancement

[Chandra Kurniawan]

Image is 2D matrix.

But, don't be worry!

Matlab also provide medfilt2 for 2D median filtering.

[Walter Roberson]

color images are 3D matrices.

[Chandra Kurniawan]

Yes, I meant 3D matrix

That right function medfilt2 works on 2D image array.

Then, you can use the same function to filter rgb <color> image plane by plane.

I mean you need to apply this to red plane, green plane, blue plane one-by-one.

Here I give you sample code :

I = imread('peppers.png');

J = imnoise(I,'salt & pepper');

imshow(J);

K(:,:,1) = medfilt2(J(:,:,1));

K(:,:,2) = medfilt2(J(:,:,2));

K(:,:,3) = medfilt2(J(:,:,3));

figure, imshow(K);

Answer 2

[Image Analyst]

Whether applying medfilt2() to each color plane independently (such as my code here: http://www.mathworks.com/matlabcentral/answers/16350-how-to-remove-pixels-in-an-image) is an improvement is something you'll have to decide as this can give color artifacts that can make it worse. Maybe you want to convert to HSV and just use medfilt2 on the V channel. Or you can do more sophisticated, smarter things like median filtering the image (somehow) and then replace only SOME of the pixels - the "bad" ones, which you've identified somehow - rather than all of them.

Answer 3

[Yogesh Joshi]

I think using medfilt2 for each color plane will not give good results,instead treat each pixel as vector and use vector median filter algorithm

[Image Analyst]

OK, what's the algorithm for that?