MATLAB PROGRAM : 2D MEDIAN FILTERING FOR SALT AND PEPPER NOISE WITHOUT USING medfilt2 FUNCTION

MEDIAN FILTER:
In digital Image processing, removing the noise is one of the preprocessing techniques.

The image noise may be termed as random variation of brightness or color information.

There are various types of image noise. Here a matlab program to remove 'salt and pepper noise' using median filtering is given.

  The random occurrence of black and white pixels is ‘salt and pepper noise’.
Learn how to add 'salt and pepper noise to an image'.

Median filtering preserves the image without getting blurred. Median filtering is done on an image matrix by   finding the median of the neighborhood pixels by using a window that slides pixel by pixel.

The procedural steps for 2D median filtering

Learn how to pad with zeros using MATLAB built_in function padarray.

FLOW CHART:

MATLAB CODE:

%READ AN 2D IMAGE

A=imread('zebra.jpg');

title('IMAGE WITH SALT AND PEPPER NOISE');

figure,imshow(A);

%PAD THE MATRIX WITH ZEROS ON ALL SIDES

modifyA=zeros(size(A)+2);

B=zeros(size(A));

%COPY THE ORIGINAL IMAGE MATRIX TO THE PADDED MATRIX

        for x=1:size(A,1)

            for y=1:size(A,2)

                modifyA(x+1,y+1)=A(x,y);

            end

        end

      %LET THE WINDOW BE AN ARRAY

      %STORE THE 3-by-3 NEIGHBOUR VALUES IN THE ARRAY

      %SORT AND FIND THE MIDDLE ELEMENT

       

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

    for j=1:size(modifyA,2)-2

        window=zeros(9,1);

        inc=1;

        for x=1:3

            for y=1:3

                window(inc)=modifyA(i+x-1,j+y-1);

                inc=inc+1;

            end

        end

       

        med=sort(window);

        %PLACE THE MEDIAN ELEMENT IN THE OUTPUT MATRIX

        B(i,j)=med(5);

       

    end

end

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

B=uint8(B);

title('IMAGE AFTER MEDIAN FILTERING');

figure,imshow(B);