boundary extraction

Boundary Extraction

The goal of boundary extraction is to find the pixels that are on the boundary of objects in the image.

Course Name: Digital Image Processing Level(UG/PG): UG Author(s) : Phani Swathi ChittaMentor: Prof. Saravanan Vijayakumaran

*The contents in this ppt are licensed under Creative Commons Attribution-NonCommercial-ShareAlike 2.5 India license

Learning ObjectivesAfter interacting with this Learning Object, the learner will be able to:• Explain the basic morphological Algorithm (Boundary Extraction)

Definitions of the components/Keywords:

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1 • The boundary of a set A, denoted as β(A), can be obtained by first eroding A by B and then performing the set difference between A and its erosion as follows: where B is a suitable structuring element.

• To extract boundary of a set A:

- First erode A (make A smaller) using structuring element B- A – erode(A)

• The thicker boundaries can be obtained by increasing the size of structuring element.

Master Layout 1

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• Give radio buttons to select any one structuring element of sizes 5x5, 7x7, 11x11 • The structuring elements (SE) are

Image after boundary extraction Original Image

Step 1: 1

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4Instruction for the animator Text to be displayed in the working area (DT)

• Show the original image first then show the structuring element selected by the user

• The text in DT should appear in parallel to the figures

• The original image• The structuring element

Step 2: 1

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SE 5x5

Instruction for the animator Text to be displayed in the working area (DT)• The SE must move on the original image

such that the center of the SE must move pixel by pixel on the original image


• The left image is the original image.• The Structuring Element is moving on the image such that the center of SE

moves pixel by pixel.• The SE used for erosion is of size 5x5

Step 3: 1

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• The SE must move on the original image such that the center of the SE must move pixel by pixel on the original image




Step 4: 1

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Step 5: 1

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Step 6: 1

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Step 7: 1

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SE 7x7






Step 8: 1

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Step 9: 1

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Step 10: 1

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Step 11: 1

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Step 12: 1

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SE 11x11






Step 13: 1

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Introduction

Credits

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Definitions Test your understanding (questionnaire) Lets Sum up (summary) Want to know more…

(Further Reading)

Try it yourself

Interactivity:

Analogy

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Slide 23, 24,25

Slide 26

Electrical Engineering

Select any one of the figures a b c d

Select the size of structuring element

Questionnaire

1.If the size of Structuring Element increases, what happens to the width of the boundary?

Answers: a) Increase b) Decrease

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Questionnaire2.

Image A Image B:Structuring Element(7x7) What is the boundary extracted image of ‘A’ using structuring

element (image B)?

Answers: a) b)

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Questionnaire2.

Image a Image b:Structuring Element(7x7) What is the resulting image after eroding the image a using

structuring element (image b)?

Answers: c) d)

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Links for further readingReference websites:http://www.ee.lamar.edu/gleb/dip/10-2%20-%20Morphological

%20Image%20Processing.pdfhttp://faraday.ee.emu.edu.tr/ee583/Lectures/EE%20583-

Lecture10.pdf

Books:Digital Image Processing – Rafael C. Gonzalez,

Richard E. Woods, Third edition, Prentice Hall

boundary extraction

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