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cvMedianFilter2.m
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cvMedianFilter2.m
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function O = cvMedianFilter2(I, wsize)
% cvMedianFilter2 - 2D Median filter
%
% Synopsis
% [O] = cvMedianFilter2(I, wsize)
%
% Description
% 2D Median filter. This accepts color image input too.
%
% Inputs ([]s are optional)
% (matrix) I N x M x C matrix representing the input image
% (vector) wsize A scalar or 1 x 2 vector representing the size of
% (scalar) filter window. The number should be odd.
% A scalar specifies square window size.
%
% Outputs ([]s are optional)
% (matrix) O N x M x C matrix representing the output image
%
% See also
% medfilt2, ordfilt2 (Image Processing Toolbox)
%
% Examples
% I = imread('image/lena.png');
% I = imnoise(I,'salt & pepper',0.02);
% O = uint8(cvMedianFilter2(I, [3 3]));
% figure; imshow(I);
% figure; imshow(O);
% % Use medfilt2 in practice where almost equivalent codes are as
% for c = 1:size(I, 3)
% O(:,:,c) = medfilt2(I(:,:,c), [3 3], 'symmetric');
% end
% % Or ordfilte2
% domain = ones(3, 3);
% order = ceil(prod(wsize) / 2);
% for c = 1:size(I, 3)
% O(:,:,c) = ordfilt2(I(:,:,c), order, domain, 'symmetric');
% end
% Authors
% Naotoshi Seo <sonots(at)sonots.com>
%
% License
% The program is free to use for non-commercial academic purposes,
% but for course works, you must understand what is going inside to use.
% The program can be used, modified, or re-distributed for any purposes
% if you or one of your group understand codes (the one must come to
% court if court cases occur.) Please contact the authors if you are
% interested in using the program without meeting the above conditions.
%
% Changes
% 10/01/2006 First Edition
if isscalar(wsize)
wysize = floor(wsize/2); wxsize = floor(wsize/2);
else
wysize = floor(wsize(1)/2); wxsize = floor(wsize(2)/2);
end
if ~isa(I, 'double')
I = double(I);
end
%% Ignore outside boundary
[nRow, nCol, C] = size(I);
for x = 1:nCol
Wx = (x - wxsize) : (x + wxsize);
Wx = Wx(Wx >= 1 & Wx <= nCol);
for y = 1:nRow
Wy = (y - wysize) : (y + wysize);
Wy = Wy(Wy >= 1 & Wy <= nRow);
O(y, x, :) = median(reshape(I(Wy, Wx, :), length(Wx)*length(Wy), [], C));
end
end