Digital Image ProcessingAsad Ali. From BCS 6th

3395

What is Image Arithmetic?

Image arithmetic is the implementation of standard

arithmetic operations

What is Image Arithmetic?

Image arithmetic is the implementation of standard

arithmetic operations, such as

• Addition

What is Image Arithmetic?

Image arithmetic is the implementation of standard

arithmetic operations, such as

• Addition

• Subtraction

What is Image Arithmetic?

Image arithmetic is the implementation of standard

arithmetic operations, such as

• Addition

• Subtraction

• Multiplication

What is Image Arithmetic?

Image arithmetic is the implementation of standard

arithmetic operations, such as

• Addition

• Subtraction

• Multiplication

• Division

IA JUICED UP!!

Usage of Image Arithmetic

Image arithmetic has many uses in image processing both as a preliminary step in more complex operations and by itself.

For example:

Image subtraction can be used to detect differences

between two or more images of the same scene or

object.

HOW/WHERE you can useImage Arithmetic?

You can do image arithmetic using the MATLAB arithmetic

operators.

HOW/WHERE you can useImage Arithmetic?

You can do image arithmetic using the MATLAB arithmetic

operators.

But:-

Wait Wait Wait..!!!!!

HOW/WHERE you can useImage Arithmetic?

You can do image arithmetic using the MATLAB arithmetic

operators.

But remember to:

• Convert the images to class.

AND

• Double to use these operators.

Adding Images

To add two images or add a constant value to an image.

Adding Images

To add two images or add a constant value to an image.

• [imadd] functionadds the value of each pixel in one of the input images with the

corresponding pixel in the other input image and returns the

sum in the corresponding pixel of the output image.

USAGE of Adding Images

Image addition has many uses in image processing.

For example:

The following code fragment uses addition to superimpose one

image on top of another. The images must be the same size and

class. You can brighten your image too.

USAGE of Adding Images

Image addition has many uses in image processing.

For example:

The following code fragment uses addition to superimpose one

image on top of another. The images must be the same size and

class. You can brighten your image too.

I = imread(‘pic1.tif');

J = imread(‘pic2.tif');

K = imadd(I,J);

imshow(K)

USAGE of Adding Images

Image addition has many uses in image processing.

For example:

The following code fragment uses addition to superimpose one

image on top of another. The images must be the same size and

class. You can brighten your image too.

I = imread(‘pic1.tif');

J = imread(‘pic2.tif');

K = imadd(I,J);

imshow(K)

Multiplying Images

[immultiply] function.This does an element-by-element multiplication (.*) of each corresponding pixel in a pair

of input images and returns the product of these multiplications

in the corresponding pixel in an output image.

Multiplying Images

[immultiply] function.This does an element-by-element multiplication (.*) of each corresponding pixel in a pair

of input images and returns the product of these multiplications

in the corresponding pixel in an output image.

Scaling image processing operations.

Scaling brightens an image; a factor less than one darkens an image.

Scaling generally produces a much more natural brightening/darkening effect than simply adding an offset to the

pixels, since it preserves the relative contrast of the image better. For example, this code scales an image by a constant factor.

Multiplying Images Example Code

I = imread(‘pic.tif');

J = immultiply(I,1.2);

imshow(I);

figure, imshow(J);

Summary of Image Arithmetic Functions

Function Description

imabsdiff Absolute difference of two images

Imadd Add two images

imcomplement Complement an image

imdivide Divide two images

imlincomb Compute linear combination of two images

immultiply Multiply two images

imsubtract Subtract two images