DIGITAL IMAGE PROCESSING
LAB












NEIL MATHEW – 7CS4 – Y3305 - A2324710002
 
INDEX
Date	S.No & Title & Page No	Sign
	Q1 WRITE A PROGRAM TO DISPLAY THE NEGATIVE OF AN IMAGE.	3
Q2  WRITE A PROGRAM TO DISPLAY LOG TRANSFORMATION OF AN IMAGE.	4
Q3 WRITE A PROGRAM TO DISPLAY THE ANTILOG TRANSFORMATION OF AN IMAGE.	5
Q4 WRITE A PROGRAM TO DISPLAY A FILTERED IMAGE AFTER PASSING IT TO A IDEAL LOW PASS FILTER.	6
Q5  WRITE A PROGRAM TO DISPLAY A FILTERED IMAGE AFTER PASSING IT TO A IDEAL HIGH PASS FILTER.	8
Q6 WRITE A PROGRAM TO DISPLAY A FILTERED IMAGE AFTER PASSING IT TO A BUTTERWORTH LOW PASS FILTER.	10
Q7 WRITE A PROGRAM TO DISPLAY A FILTERED IMAGE AFTER PASSING IT TO A GAUSSIAN LOW PASS FILTER.	12
Q8 WRITE A PROGRAM TO PERFORM LAPLACE TRANSFORM OF AN IMAGE.	14
Q9 WRITE A PROGRAM TO CALCULATE THE GRADIENT OF THE IMAGE.	16
Q10 WRITE A PROGRAM TO PERFORM ARITHMETIC OPERATIONS ON AN   IMAGE.	17
Q11 WRITE A PROGRAM TO FIND THE THRESHOLD IMAGE AT ANY THRESHOLD POINT.	19
Q12 WRITE A PROGRAM TO PERFORM BUTTERWORTH HIGH PASS FILTER ON AN IMAGE.	20
Q13 WRITE A PROGRAM TO PERFORM GAUSSIAN HIGH PASS FILTER ON AN IMAGE.	22
Q14 WRITE A PROGRAM TO PERFORM EROSION, DILATION, BOUNDARY EXTRACTION ON AN IMAGE.	24


Q1 Write a program to display the negative of an image.

a=imread('C:\Users\Desktop\lena.png');
subplot(2,2,1);
imshow(a);
title('original image');
 b=rgb2gray(a);
subplot(2,2,2);
imshow(b);
title('gray scale image');
 c=255-a;
subplot(2,2,3);
imshow(c);
title('negative of image');
 d=255-b;
subplot(2,2,4);
imshow(d);
title('negaative of gray scale image');

OUTPUT:

 



Q2  Write a program to display log transformation of an image.

a=imread('C:\Users\Desktop\lena.png');
subplot(2,2,1);
imshow(a);
title('original image');
b=im2double(a);
subplot(2,2,2);
imshow(b);
title('double of an image');
c=log(1+b);
subplot(2,2,3);
imshow(c);
title('log of an image'); 
d=log2(1+b);
subplot(2,2,4);
imshow(d);
title('log to the base 2');
 
OUTPUT:

 
 
Q3 Write a program to display the antilog transformation of an image.
a=imread('C:\Users\Desktop\lena.png');
subplot(2,2,1);
imshow(a);
title('original image');
b=im2double(a);
subplot(2,2,2);
imshow(b);
title('Double of image');
c=log10(1+b);
subplot(2,2,3);
imshow(c);
title('log10 of an image');
d=exp(b)/10;
subplot(2,2,4);
imshow(d);
title('antilog of an image');

OUTPUT:

 
 
Q4 Write a program to display a filtered image after passing it to a ideal low pass filter.

a=imread('C:\Users\Desktop\lena2.png');
b=double(a);
[m n]=size(a);
d0=input('enter the cut off frequency');
for u=1:1:m
    for v=1:1:n
        d=((u-m/2)^2+(v-n/2)^2)^0.5;
        if(d<d0)
            H(u,v)=1;
        else
            H(u,v)=0;
        end
    end
end
fouriertrans=fft2(b,size(H,1),size(H,2));
shiftedfouriertrans=fftshift(fouriertrans);
x=shiftedfouriertrans.*H;
X=abs(ifft2(x));
filtered_image=uint8(X);
filtered_image = filtered_image(1:size(a, 1), 1:size(a, 2));
subplot(2,2,1);
imshow(a);
title('original image');
subplot(2,2,2);
imshow(filtered_image);
title('Filtered Image'); 
subplot(2,2,3);
imshow(H);
title('Ideal low pass filter');
subplot(2,2,4);
mesh(H),colormap(gray);
title 'Ideal low pass frequency response';
 
 
OUTPUT:

 
 
Q5  Write a program to display a filtered image after passing it to a ideal high pass filter.

a=imread('C:\Users\Desktop\lena2.png');
b=double(a);
[m n]=size(a);
d0=input('enter the cut off frequency');
for u=1:1:m
    for v=1:1:n
        d=((u-m/2)^2+(v-n/2)^2)^0.5;
        if(d<d0)
            H(u,v)=0;
        else
            H(u,v)=1;
        end
    end
end
fouriertrans=fft2(b,size(H,1),size(H,2));
shiftedfouriertrans=fftshift(fouriertrans);
x=shiftedfouriertrans.*H;
X=abs(ifft2(x));
filtered_image=uint8(X);
filtered_image = filtered_image(1:size(a, 1), 1:size(a, 2));
subplot(2,2,1);
imshow(a);
title('original image');
subplot(2,2,2);
imshow(filtered_image);
title('Filtered Image'); 
subplot(2,2,3);
imshow(H);
title('Ideal high pass filter');
subplot(2,2,4);
mesh(H),colormap(gray);
title 'Ideal high pass frequency response';
 
 

OUTPUT:

 
 

Q6 Write a program to display a filtered image after passing it to a Butterworth low pass filter.


a=imread('C:\Users\Desktop\lena2.png');
b=double(a);
[m n]=size(a);
d0=input('enter the cut off frequency');
n0=input('enter  value of n');
for u=1:1:m
    for v=1:1:n
        d=((u-m/2)^2+(v-n/2)^2)^0.5;
        H(u,v)=1/(1+(d/d0))^2*n0;
    end
end
   fouriertrans=fft2(b,size(H,1),size(H,2));
shiftedfouriertrans=fftshift(fouriertrans);
x=shiftedfouriertrans.*H;
X=abs(ifft2(x));
filtered_image=uint8(X);
filtered_image = filtered_image(1:size(a, 1), 1:size(a, 2));
subplot(2,2,1);
imshow(a);
title 'original image';
subplot(2,2,2);
mesh(H),colormap(gray);
title 'butterworth low pass frequency response';
subplot(2,2,3);
imshow(filtered_image);
title 'Filtered Image';
subplot(2,2,4);
imagesc(H), colormap(gray);
title 'butterworth low pass filter';

 
OUTPUT:

 
 

Q7 Write a program to display a filtered image after passing it to a Gaussian low pass filter.

a=imread('C:\Users\Desktop\lena2.png');
b=double(a);
[m n]=size(a);
d0=input('enter the cut off frequency');
for u=1:1:m
    for v=1:1:n
        d=((u-m/2)^2+(v-n/2)^2)^0.5;
        H(u,v)=exp((-d*d)/(2*d0*d0));
    end
end
fouriertrans=fft2(b,size(H,1),size(H,2));
shiftedfouriertrans=fftshift(fouriertrans);
x=shiftedfouriertrans.*H;
X=abs(ifft2(x));
filtered_image=uint8(X);
filtered_image = filtered_image(1:size(a, 1), 1:size(a, 2));
subplot(2,2,1);
imshow(a);
title 'original image';
subplot(2,2,2);
mesh(H),colormap(gray);
title 'Gausian low pass frequency response';
subplot(2,2,3);
imshow(filtered_image);
title 'Filtered Image';
subplot(2,2,4);
imagesc(H), colormap(gray);
title 'gausian low pass filter';

 
OUTPUT:

 
 
Q8 Write a program to perform laplace transform of an image.

clc;
a=imread('C:\Users\Desktop\lena color.png');
z=im2double(a);
s=del2(z);
s1=3*s;
s2=z-s1;
subplot(2,2,1);
imshow(a);
title('Original image');
subplot(2,2,2);
imshow(s);
title('Laplace of an image');
subplot(2,2,3);
imshow(s2);
title('Sharpen image');
 

OUTPUT:

 
 
Q9 Write a program to calculate the gradient of the image.

clc;
a=imread('C:\Users\Desktop\lena color.png');
z=im2double(a);
s=gradient(z);
s1=4*s;
s2=z-s1;
subplot(2,2,1);
imshow(a);
title('original');
subplot(2,2,2);
imshow(s);
title('gradient of an image');
subplot(2,2,3);
imshow(s2);
title('Sharpen image');

OUTPUT:	

 

Q10 Write a program to perform arithmetic operations on an   image.

a=imread('C:\Users\Desktop\lena.png');
b=imread('C:\Users\Desktop\lena color.png');
subplot(3,3,1);
imshow(a);
title 'image1';
subplot(3,3,2);
imshow(b);
title 'image2';
c=a+b;
subplot(3,3,3);
imshow(c);
title 'added image';
d=b-a;
subplot(3,3,4);
imshow(d);
title 'substracted image';
e=a.*5;
subplot(3,3,5);
imshow(e);
title 'multiplied image';
f=b./2;
subplot(3,3,6);
imshow(f);
title 'divided image';
 

OUTPUT:

 

 
Q11 Write a program to find the threshold image at any threshold point.

a=imread('C:\Users\Desktop\lena color.png');
b=a;
k=120;
[m,n]=size(a);
for i=1:m
for j=1:n
if(a(i,j)>=k)
b(i,j)=255;
else (a(i,j)<=1)
b(i,j)=0;
end
end
end
subplot(2,2,1)
imshow(a)
title('original image');
subplot(2,2,2)
imshow(b);
title('changed image');

OUTPUT:

 


Q12 Write a program to perform butterworth high pass filter on an image.

a=imread('C:\Users\Desktop\lena2.png');
b=double(a);
[m n]=size(a);
d0=input('enter the cut off frequency');
n0=input('enter  value of n');
for u=1:1:m
    for v=1:1:n
        d=((u-m/2)^2+(v-n/2)^2)^0.5;
        H(u,v)=1/(1+(d0/d))^2*n0;
    end
end
   fouriertrans=fft2(b,size(H,1),size(H,2));
shiftedfouriertrans=fftshift(fouriertrans);
x=shiftedfouriertrans.*H;
X=abs(ifft2(x));
filtered_image=uint8(X);
filtered_image = filtered_image(1:size(a, 1), 1:size(a, 2));
 
subplot(2,2,1);
imshow(a);
title 'original image';
subplot(2,2,2);
mesh(H),colormap(gray);
title 'butterworth high pass frequency response';
subplot(2,2,3);
imshow(filtered_image);
title 'Filtered Image';
subplot(2,2,4);
imagesc(H), colormap(gray);
title 'butterworth high pass filter';

 
OUTPUT:

 
 
Q13 Write a program to perform gaussian high pass filter on an Image.

a=imread('C:\Users\Desktop\lena2.png');
b=double(a);
[m n]=size(a);
d0=input('enter the cut off frequency');
for u=1:1:m
    for v=1:1:n
        d=((u-m/2)^2+(v-n/2)^2)^0.5;
        H(u,v)=1-exp((-d*d)/(2*d0*d0));
    end
end
fouriertrans=fft2(b,size(H,1),size(H,2));
shiftedfouriertrans=fftshift(fouriertrans);
x=shiftedfouriertrans.*H;
X=abs(ifft2(x));
filtered_image=uint8(X);
filtered_image = filtered_image(1:size(a, 1), 1:size(a, 2));
subplot(2,2,1);
imshow(a);
title 'original image';
subplot(2,2,2);
mesh(H),colormap(gray);
title 'Gausian high pass frequency response';
subplot(2,2,3);
imshow(filtered_image);
title 'Filtered Image';
subplot(2,2,4);
imagesc(H), colormap(gray);
title 'gausian high pass filter';

 
OUTPUT:

 
                                                                  
                                                                     
                                                                     
 
Q14 Write a program to perform erosion, dilation, boundary extraction on an image.

originalBW = imread('circles.png');  
se = strel('disk',11);        

erodedBW = imerode(originalBW,se);
dilateBW = imdilate(originalBW,se);

bw1 = imdilate(erodedBW,se);
bw2 = imerode(dilateBW,se);

boundary = originalBW - erodedBW;

hm1 = bwhitmiss

subplot(3,3,1);
imshow(originalBW);
title('Original');

subplot(3,3,2);
imshow(erodedBW);
title('Original Eroded');

subplot(3,3,3);
imshow(dilateBW);
title('Original Dilated');

subplot(3,3,4);
imshow(bw1);
title('Opening');

subplot(3,3,5);
imshow(bw2);
title('Closing');

subplot(3,3,6);
imshow(boundary);
title('Boundary');

 

OUTPUT: