Median filter for rgb images

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FIR
FIR 2012년 9월 8일
편집: DGM 2023년 1월 9일 13:14
For 2d images for performing median filtering we have inbuilt function medfilt2
is there any function for performing median filtering rgb images

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Image Analyst
Image Analyst 2012년 9월 8일
The help is a good place to look for this information. If you type in median there, you'll see that you can use medfilt2() in the Image Processing Toolbox. I have a demo that uses medfilt2() to remove salt and pepper noise in RGB images, if you want to see it.
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Latha
Latha 2017년 7월 14일
Thank you Analyst!!!

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Jürgen
Jürgen 2012년 9월 8일
Hey,
I would perform it on one of the channels depinding on which features afterwards you want to extract, or perform it on each channel.
or first transform to an other color space
regardsJ

Noor Abbas
Noor Abbas 2016년 10월 16일
Hello every one, Could you please help with code for adaptive medium filter. Thanks
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Image Analyst
Image Analyst 2017년 9월 12일
So start a new question and attach your/my code, and your image, and explain what help you need, such as why it's not working the way you like, or some error that your code (after you modified mine) is throwing.

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DGM
DGM 2023년 1월 9일 13:02
편집: DGM 2023년 1월 9일 13:14
If you want something akin to medfilt2() that works with multichannel images, then you have a few options.
% an RGB uint8 image
inpict = imread('peppers.png');
inpict = imresize(inpict,0.5);
% window size
ws = [11 11];
% using nlfilter() (slow)
sz = size(inpict);
op1 = zeros(sz,class(inpict));
for c = 1:size(inpict,3)
op1(:,:,c) = nlfilter(inpict(:,:,c),ws,@(x) median(x(:)));
end
% using medfilt2()
sz = size(inpict);
op2 = zeros(sz,class(inpict));
for c = 1:size(inpict,3)
op2(:,:,c) = medfilt2(inpict(:,:,c),ws,'symmetric');
end
% using medfilt3() (R2016b or newer)
op3 = medfilt3(inpict,[ws 1]);
% using MIMT nhfilter()
op4 = nhfilter(inpict,'median',ws);
Note that the last three examples have identical output for the specified options, whereas nlfilter() has no padding options, and will exhibit edge effects (pay attention to the corners). IPT medfilt2() will behave similarly with the default padding option.
Using nlfilter() for something simple like a median filter isn't really practical in comparison, but it is an option.
The first three tools are from the Image Processing Toolbox, whereas nhfilter() is from MIMT. While nhfilter() does not require IPT, it will run much faster if IPT is installed.
If instead of what OP asked, you want a noise removal filter instead, you have a few options. You can either reimplement the whole thing, or you can find one. MIMT has two options.
% an RGB uint8 image
inpict0 = imread('peppers.png');
inpict0 = imresize(inpict0,0.5);
% add noise
inpict = imnoise(inpict0,'salt & pepper',0.2);
% use a fixed-window median noise removal filter (similar to IA's demo)
op1 = fmedfilt(inpict,11);
% use an adaptive median noise removal filter
op2 = amedfilt(inpict,5);
See also:

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