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Image Erosion without using MATLAB function 'imerode'

In MATLAB, ‘imerode’ is a function used to make the objects thin. MATLAB code without using 'imerode' function and explanation is provided here.



MATLAB CODE:



A=[1 0 1 1 1; 1 0 1 0 0; 1 1 1 0 0;0 0 1 1 1];
%Structuring element
B=[1 1 0];
%Pad array with ones on both sides
C=padarray(A,[0 1],1);
%Intialize the matrix D of size A with zeros
D=false(size(A));
for i=1:size(C,1)
    for j=1:size(C,2)-2
        In=C(i,j:j+2);
        %Find the position of ones in the structuring element
        In1=find(B==1);
        %Check whether the elements in the window have the value one in the
        %same positions of the structuring element
        if(In(In1)==1)
        D(i,j)=1;
        end
    end
end
display(D);


Explanation:
1.     Consider a matrix A and a structuring element B.
2.     Initialize a matrix D of size A with zeros.
3.     Construct a window of size B with the elements of matrix A.
4.     Check whether the ones in the structuring element B overlap the ones in the window.
5.     If it overlaps, then update D with one else zero.





Example 2:


A=imread('circles.png');
figure,imshow(A);
Original Image









%Structuring element
B=getnhood(strel('disk',11));

m=floor(size(B1,1)/2);
n=floor(size(B1,2)/2);
%Pad array on all the sides
C=padarray(A,[m n],1);
%Intialize a matrix with size of matrix A
D=false(size(A));
for i=1:size(C,1)-(2*m)
    for j=1:size(C,2)-(2*n)
       
        Temp=C(i:i+(2*m),j:j+(2*n));
       
        D(i,j)=min(min(Temp-B1));
      
    end
end
figure,imshow(~D1);


After Erosion
  

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Image Dilation without using 'imdilate' function


           In MATLAB, ‘imdilate’is the function that dilates the image using a structuring element. Let’s learn how this function works using some examples and codes.


MATLAB CODE:


Example 1:

A=[1 0 0 0 1; 1 0 1 0 0; 1 1 1 0 0;0 0 1 1 1];
%Structuring element
B=[1 0 0; 0 1 0; 0 0 1];
%Pad zeros on all the sides
C=padarray(A,[1 1]);
%Intialize a matrix of matrix size A with zeros
D=false(size(A));
for i=1:size(C,1)-2
    for j=1:size(C,2)-2
        %Perform logical AND operation
        D(i,j)=sum(sum(B&C(i:i+2,j:j+2)));
    end
end

display(D);

Example 2:
A=imread('text.png');
Original Image



A=im2bw(A);
%Structuring element
B2=getnhood(strel('line',7,90));
m=floor(size(B2,1)/2);
n=floor(size(B2,2)/2);
%Pad array on all the sides
C=padarray(A,[m n]);
D=false(size(A));
for i=1:size(C,1)-(2*m)
    for j=1:size(C,2)-(2*n)
        Temp=C(i:i+(2*m),j:j+(2*n));
        D(i,j)=max(max(Temp&B2));
    end
end

figure,imshow(D);

Dilated Image



Example 3:(Method 2)

A=imread('text.png');
A=im2bw(A);
%Structuring element
B=[1 1 1 1 1 1 1;];
C=padarray(A,[0 3]);
D=false(size(A));
for i=1:size(C,1)
    for j=1:size(C,2)-6
        D(i,j)=sum(B&C(i,j:j+6));
    end
end
figure,imshow(D);



Dilated image



























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