update medianFilter.m

Author: dlegland

src/@Image/medianFilter.m

@@ -1,14 +1,18 @@
 function res = medianFilter(obj, se, varargin)
 % Compute median value in the neighboorhood of each pixel.
 %
+%   RES = medianFilter(IMG2D, [M N])
+%   RES = medianFilter(IMG3D, [M N P])
+%   Applies median filtering to the input image, by computing the median
+%   value in the square or cubic neighborhood of each image element. 
+%
 %   RES = medianFilter(IMG, SE)
-%   Compute the mean filter of image IMG, using structuring element SE.
-%   The goal of obj function is to provide the same interface as for
-%   other image filters (imopen, imerode ...), and to allow the use of 
-%   mean filter with user-defined structuring element. 
+%   Compute the median filter of image IMG, using structuring element SE.
+%   The goal of this function is to provide the same interface as for
+%   other image filters (opening, erosion...), and to allow the use of 
+%   median filter with user-defined structuring element. 
 %   This function can be used for directional filtering.
 %
-%
 %   RES = medianFilter(IMG, SE, PADOPT) 
 %   also specify padding option. PADOPT can be one of:
 %     'zeros'
@@ -17,21 +21,28 @@
 %   see ordfilt2 for details. Default is 'symmetric' (contrary to the
 %   default for ordfilt2).
 %
+%   Implementation notes
+%   When neighborhood is given as a 1-by-2 or 1-by-3 array, the methods is
+%   a wrapper for the medfilt2 or medfilt3 function. Otherwise, the
+%   ordfilt2 function ise used.
+%
+%   Example
+%     % apply median filtering on rice image
+%     img = Image.read('rice.png');
+%     imgf = medianFilter(img, [3 3]);
+%     figure; show(imgf);
+%   
 %   See also:
 %     meanFilter, ordfilt2, median
 %
 
 % ------
 % Author: David Legland
-% e-mail: david.legland@inra.fr
+% e-mail: david.legland@inrae.fr
 % Created: 2011-08-05,    using Matlab 7.9.0.529 (R2009b)
 % Copyright 2011 INRA - Cepia Software Platform.
 
 
-if obj.Dimension > 2
-    error('Median filter implemented only for planar images');
-end
-
 % transform STREL object into single array
 if isa(se, 'strel')
     se = getnhood(se);
@@ -43,13 +54,26 @@
     padopt = varargin{1};
 end
 
-% rotate structuring element
-se = permute(se, [2 1 3:5]);
-
-% perform filtering
-order = ceil(sum(se(:)) / 2);
-data = ordfilt2(obj.Data, order, se, padopt);
+if isnumeric(se) && all(size(se) == [1 2]) && obj.Dimension == 2
+    % if input corresponds to filter size, use medfilt2
+    data = medfilt2(obj.Data, se([2 1]));
+    
+elseif isnumeric(se) && all(size(se) == [1 3]) && obj.Dimension == 3
+    % process the 3D case, only for cubic neighborhoods
+    data = medfilt3(obj.Data, se([2 1 3]));
+    
+else
+    % otherwise, use the ordfilt2 function by choosing the order according
+    % to SE size.
+    
+    % rotate structuring element
+    se = permute(se, [2 1 3:5]);
+    
+    % perform filtering
+    order = ceil(sum(se(:)) / 2);
+    data = ordfilt2(obj.Data, order, se, padopt);
+end
 
 % create result image
 name = createNewName(obj, '%s-medianFilt');
-res = Image('Data', data, 'Parent', obj, 'Name', name);
+res = Image('Data', data, 'Parent', obj, 'Name', name);

tests/image/test_medianFilter.m

@@ -0,0 +1,49 @@
+function tests = test_medianFilter
+% Test suite for the file medianFilter.
+%
+%   Test suite for the file medianFilter
+%
+%   Example
+%   test_medianFilter
+%
+%   See also
+%     medianFilter
+
+% ------
+% Author: David Legland
+% e-mail: david.legland@inrae.fr
+% Created: 2021-11-19,    using Matlab 9.10.0.1684407 (R2021a) Update 3
+% Copyright 2021 INRAE - BIA-BIBS.
+
+tests = functiontests(localfunctions);
+
+function test_2d_Size(testCase) %#ok<*DEFNU>
+% Test call of function without argument.
+
+img = Image.read('rice.png');
+
+res = medianFilter(img, [3 3]);
+
+assertEqual(testCase, size(res), size(img));
+
+
+function test_2d_array(testCase) %#ok<*DEFNU>
+% Test call of function without argument.
+
+img = Image.read('rice.png');
+
+se = [0 1 0;1 1 1;0 1 0];
+res = medianFilter(img, se);
+
+assertEqual(testCase, size(res), size(img));
+
+
+function test_3d_Size(testCase) %#ok<*DEFNU>
+% Test call of function without argument.
+
+img = Image(ones([7 7 7]));
+
+res = medianFilter(img, [3 3 3]);
+
+assertEqual(testCase, size(res), size(img));
+