Min Filter - MATLAB CODE

MIN FILTER

•      To find the darkest points in an image.
•       Finds the minimum value in the area encompassed by the filter.
•       Reduces the salt noise as a result of the min operation.
•       The 0^th percentile filter is min filter.

The MIN Filtering is similar to MAX filter. Check MAX filter post to know how the formula is used to filter the pepper noise.

MATLAB CODE:

%READ AN IMAGE

A = imread('board.tif');

A = rgb2gray(A(1:300,1:300,:));

figure,imshow(A),title('ORIGINAL IMAGE');

%PREALLOCATE THE OUTPUT MATRIX

B=zeros(size(A));

%PAD THE MATRIX A WITH ZEROS

modifyA=padarray(A,[1 1]);

        x=[1:3]';

        y=[1:3]';

       

for i= 1:size(modifyA,1)-2

    for j=1:size(modifyA,2)-2

      

       %VECTORIZED METHOD 

       window=reshape(modifyA(i+x-1,j+y-1),[],1);

       %FIND THE MINIMUM VALUE IN THE SELECTED WINDOW

        B(i,j)=min(window);

    end

end

%CONVERT THE OUTPUT MATRIX TO 0-255 RANGE IMAGE TYPE

B=uint8(B);

figure,imshow(B),title('IMAGE AFTER MIN FILTERING');