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Introduction to Image ProcessingIntroduction to Image Processing

Dr. Kourosh KianiEmail: kkiani2004@yahoo.comEmail: Kourosh.kiani@aut.ac.irEmail: Kourosh.kiani@semnan.ac.irWeb: www.kouroshkiani.com

Present to:Amirkabir University of Technology (Tehran

Polytechnic) & Semnan University

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Lecture 04

Arithmetic Operations

Algebraic operations used for images are commonly viewed in two groups; mathematical and logical operations. Image adding, subtracting, dividing and multiplying operations constitute mathematical processing and “AND, OR, NOT” etc. operations forms logical operations.

SIMPLE ALGEBRAIC OPERATIONS in IMAGES

………

…a4a3

…a2a1

………

…b4b3

…b2b1a4

+b4a3

+b3

a2 +b2

a1 +b1

+ =

………

…a4a3

…a2a1a4

+10a3

+10

a2 +10

a1 +10

+ =10

IMAGE ADDITION

IMAGE ADDITION

C[x, y] A[x, y] B[x, y]

Reduce noise (increase SNR) averaging, smoothing ...

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+

=

IMAGE ADDITION

C[x, y] A[x, y] B[x, y]

I = imread(‘rice.tif’);J = imread(‘cameraman.tif’);K = imadd(I, J);imshow(K)

Ori=imread('rice.png');j=imread('cameraman.tif');k=i+j;imshow(k);

I = imread('kourosh.jpg');figure(1);imshow(I);I2 = imadd(I, 70);figure(2);imshow(I2);

+ 70 =

Image Averaging

Consider a noisy image g(x,y) formed by the addition of noise (x,y) to an original image f(x,y)

g(x,y) = f(x,y) + (x,y)

Image Averaging

If noise has zero mean and is uncorrelated then it can be shown that

),( yxg = image formed by averaging K different noisy images

K

ii yxg

Kyxg

1

),(1

),(

Image Averaging

Then

),(2

),(2 1

yxyxgK

= variances of g and ),(2

),(2 , yxyxg

Then if K increase, it indicates that the variability (noise) of the pixel at each location (x,y) decreases.

IMAGE AVERAGING

Average multiple images (frames) of the same scene together

Useful for removing noise

+ + . . . =

X = 255 10 75 44 225 100

Y = 50 50 50 50 50 50

Z = 205 0 25 0 175 50

X = uint8([ 255 10 75; 44 225 100]);Y = uint8([ 50 50 50; 50 50 50 ]);Z = imsubtract(X,Y)

Image Subtracting],[],[],[ yxByxAyxC

Image Subtractingrice = imread('rice.png');figure (1)imshow(rice);background = imopen(rice, strel('disk', 15));figure (2)imshow(background);rice2 = imsubtract(rice, background);figure (3)imshow(rice2);

- =

- 70 =

I = imread('kourosh.jpg');J = imsubtract(I,70);Figure(1), imshow(I), Figure(2), imshow(J)

Image Subtracting

_ =

Digital subtraction angiography (DSA)

Image Subtracting

Digital subtraction angiography (DSA)

Image Subtracting

X = 2 10 7 4 25 10

Y = 5 5 5 3 5 6

Z = 10 50 35 12 125 60

X = uint8([ 2 10 7; 4 25 10]);Y = uint8([ 5 5 5; 3 5 6 ]);Z = immultiply(X,Y)

Image Multiplying],[],[],[ yxByxAyxC

Image MultiplyingI = imread('moon.tif');figure(1)imshow(I)J = immultiply(I,0.5);figure(2)imshow(J)

* 0.5 =

X = 100 20 75 30 25 36

Y = 5 5 5 3 5 6

Z = 20 4 15 10 5 6

X = uint8([ 100 20 75; 30 25 36])Y = uint8([ 5 5 5; 3 5 6 ])Z = imdivide(X,Y)

Image Dividing],[],[],[ yxYyxXyxZ

Image DividingI = imread('rice.png');figure(1), imshow(I);background = imopen(I,strel('disk',15));figure(2), imshow(background);Ip = imdivide(I,background);figure(3), imshow(Ip, []);

÷ =

Image Dividing

÷ 2 =

I = imread('rice.png'); J = imdivide(I,2);figure(1), imshow(I)figure(2), imshow(J)

Questions? Discussion? Suggestions?

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