Erosion

Erosion

The basic morphological operations applied to either grayscale or binary images are Erosion and Dilation. Erosion shrinks image objects while dilation expands them.

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 operation (Erosion)

Definitions of the components/Keywords:

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1 • Characteristics of Erosion

- Erosion generally decreases the sizes of objects and removes small irregularities by subtracting objects with a span smaller than the structuring element.

- With grayscale images, erosion reduces the brightness (and therefore the size) of bright objects on a dark background by taking the neighborhood minimum when passing the structuring element over the image.

- With binary images, erosion completely removes objects smaller than the structuring element and removes perimeter pixels from larger image objects.

• The erosion operator takes two pieces of data as inputs. - The first is the image which is to be eroded. - The second is a (usually small) set of coordinate points known as a structuring element (also known as a kernel).• It is this structuring element that determines the precise effect of the erosion on the input image.

• In erosion, every object pixel that is touching a background pixel is changed into a background pixel Erosion makes the objects smaller, and can break a single object into multiple objects.

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 square and round

Image after erosion 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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4Instruction 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 of original image

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

• The left image is the original image• The

Step 3: 1

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

• The first fig. should appear and then when the slider points at sigma, the second fig. should be shown

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

• The original image• The resulting image after high boost filtering is applied• The filter mask used for smoothing is of size 3x3

Step 4: 1

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

• The first fig. should appear and then when the slider points at sigma, the second fig. should be shown

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

• The original image• The resulting image after high boost filtering is applied• The filter mask used for smoothing is of size 3x3

Step 6: 1

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

• The first fig. should appear and then when the slider points at sigma, the second fig. should be shown

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

• The original image• The resulting image after high boost filtering is applied• The filter mask used for smoothing is of size 3x3

Step 7: 1

5

32

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

• The first fig. should appear and then when the slider points at sigma, the second fig. should be shown

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

• The original image• The resulting image after high boost filtering is applied• The filter mask used for smoothing is of size 3x3

Step 8: 1

5

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

• The first fig. should appear and then when the slider points at sigma, the second fig. should be shown

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

• The original image• The resulting image after high boost filtering is applied• The filter mask used for smoothing is of size 3x3

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 structuring element

Questionnaire

1.After eroding the image, will the number of background pixels increase or decrease?

Answers: a) Increase b) Decrease

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Questionnaire2.

Image a Image b:Structuring Element What is the resulting image after eroding the image a using

structuring element (image b)?

Answers: a) b)

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Questionnaire2.

Image a Image b:Structuring Element 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://siri.lmao.sk/fiit/DSO/Prednasky/2a Morphological processing

Recap & Extend / Digital Image Processing Lecture Morphological processing Recap &Extend.pdf

http://en.wikipedia.org/wiki/Erosion_%28morphology%29http://homepages.inf.ed.ac.uk/rbf/HIPR2/erodedemo.htmhttp://homepages.inf.ed.ac.uk/rbf/HIPR2/erode.htm

Books:Digital Image Processing – Rafael C. Gonzalez,

Richard E. Woods, Third edition, Prentice Hall