__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');

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