2D majority filer in MATLAB?

Hello,

Is there a 2D majority filter in MATLAB?

With ordfilt2 minimum, maximum, median etc. filters can be implemented, but not majority. Is there another command with that functionality?

Here 'majority filter' means replacing each element of a matrix by the most frequently occurring element in a set of neighbors of that element.

Regards, Elena

[Elena Ranguelova]

Maybe

blockproc

would help?

fun = @(block_struct) ...
   mode(block_struct.data(:)) * ones(size(block_struct.data));
output_matrix = blockproc(input_matrix,[<size_x> <size_y>],fun);

Answer 1

[Sailesh Sidhwani]

There is no direct function for mode filtering, you can use the colfilt instead:

out = colfilt(img, [5 5], 'sliding', @mode) ;

Answer 2

[Sailesh Sidhwani]

A new 'modefilt' function for 2D and 3D data was added to Image Processing Toolbox in R2020a:

https://www.mathworks.com/help/images/ref/modefilt.html

Both 'colfilt' and 'nlfilter' are generic sliding window functions and can be used to perform mode filtering but the expectation is that 'modefilt' to be faster than both of these functions and also work on 3D grayscale data.

Answer 3

[rgr478]

bwmorph(image,'majority')