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Digital Image Processing Review: Computer Vision

This document provides an overview of digital image processing concepts. It discusses how images can be represented as 2D arrays of pixel values, with each pixel having an intensity value ranging from 0 to 255. It also describes how color images contain three values for red, green, and blue at each pixel location. The document reviews how images are captured digitally using sensors and color filters. It demonstrates image processing functions in Matlab like reading an image, extracting color channels, and displaying images.

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Shah Zeb Yousafzai
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75 views17 pages

Digital Image Processing Review: Computer Vision

This document provides an overview of digital image processing concepts. It discusses how images can be represented as 2D arrays of pixel values, with each pixel having an intensity value ranging from 0 to 255. It also describes how color images contain three values for red, green, and blue at each pixel location. The document reviews how images are captured digitally using sensors and color filters. It demonstrates image processing functions in Matlab like reading an image, extracting color channels, and displaying images.

Uploaded by

Shah Zeb Yousafzai
Copyright
© © All Rights Reserved
We take content rights seriously. If you suspect this is your content, claim it here.
Available Formats
Download as ODP, PDF, TXT or read online on Scribd
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Computer Vision

Lecture II
Digital Image Processing Review

By: Dr. Omar Ahmad


Lecture Contents

● Images as 2D signals.
● What are digital images?
●
CCD sensors and Color filters for Colored Images.
● Images as 2D arrays in Matlab and OpenCv
● Displaying Images.
● Cropping images
● Adding images
● Blending Images
● OpenCv basics
What is an image?

● An image can be thought of as a 2D function.


I(x,y)

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What is an image?

● Plotting the 2D image function in Matlab as a surface.

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What is an image?

● What if we smooth the function?

We observe that the


sharp peaks have
been smoothed out.

What will
happen to
the image?

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What is an image?

● We will get a 'Blurred' image.

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What is an image?

● So images can be thought of as


– A 2D array of numbers ranging from some minimum to
some maximum value
– A function I of x and y, I(x,y)
– Something captured using a camera !!

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What are digital images?

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What are digital images?

● Each image is made up of small discrete units known as


pixels (stands for Picture Elements)

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What are digital images?

● Capturing a colored image using a Bayer filter mechanism

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What are digital images?

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What are digital images?

● So now we can think of digital images as 2D functions


– I(x,y) such that
●x ranges from [a,b] and y ranges from[c,d]
● The intensity also ranges from [min,max]

● Why do intensities vary from 0 to 255?


● It is better (makes more sense) to have intensity range from
[0,1] instead.
● Colored images can also be thought of in the same way.
– I(x,y) = [ r(x,y), g(x,y), b(x,y)] T

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What are digital images?

● Can you define this image as a function?

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What are images?

● A small grid from the image will look like this.

Be careful about Rows and Columns vs x and y !!


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What is quantization?

Example: Round off to a whole number where you use a floor() function.

3.2 1.7 5.4 3.8 3.7

3.1 1.6 5.3 3.9 3.5

2.8 1.8 5.2 3.9 3.6

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Using Matlab for Image Processing

my_color_img = imread('ColoredChalk.jpg');
img_green = my_color_img(:,:,3);
imshow(my_color_img);
figure();
imshow(img_green);

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Using Matlab for Image Processing

● What size is my image?


– Use size(img) function
● What is the class of my image?
– Use the class(img) command

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