1. Image Sharpening using Laplacian
The Laplacian is a 2-D isotropic measure of the second spatial derivative of an image.
Course Name: Digital Image Processing Level: UG
Authors
Phani Swathi Chitta
Mentor
Prof. Saravanan Vijayakumaran
*The contents in this ppt are licensed under Creative Commons Attribution-NonCommercial-ShareAlike 2.5 India license

2. Learning Objectives
After interacting with this Learning Object, the learner will be able to:
Explain how the sharpening of an image is done using Laplacian

3. 1 2 3 4 5 Definitions of the components/Keywords:
The Laplacian of an image highlights regions of rapid intensity change and is therefore often used for edge detection.
Laplacian is very useful in detecting abrupt changes.
The Laplacian is often applied to an image that has first been smoothed in order to reduce its sensitivity to noise.
The Laplacian is defined as 2 3 4 5 3

4. 1 2 3 4 5 Definitions of the components/Keywords:
Filter Masks for Laplacian:
Fig. A Fig. B Fig. C
Fig. D Fig. E Fig. F
If the mask used has a negative centered coefficient (Fig. A, B, C), subtract Laplacian Image from the Input Image to obtain a sharpened Image.
If the mask used has a positive centered coefficient (Fig. D, E, F),
add Laplacian Image to the Input Image to obtain a sharpened Image. 1 1 -4 1 -8 -1 2 -4 2 -1 4 -1 8 1 -2 4 3 4 5

5. Master Layout 1
The Blurred Image
Image after sharpening 2 3
Give 3 radio buttons of filter masks so that user can select any one filter mask.
The three filter masks a, b, c are given below 4 1 -4 1 -8 -1 2 -4 5

6. 3 Step 1: 1 2 4 5 Filter mask a Instruction for the animator
Text to be displayed in the working area (DT)
The first fig. should appear and then when the radio button for first mask is selected then enable start button
After start button is clicked show the second figure
The text in DT should appear in parallel to the figures
The blurred image
The resulting image is the sharpened image after laplacian filtering mask is applied 5

7. 3 Step 2: 1 2 4 5 Filter mask b Instruction for the animator
Text to be displayed in the working area (DT)
The first fig. should appear and then when the radio button for second mask is selected then enable start button
After start button is clicked show the second figure
The text in DT should appear in parallel to the figures
The blurred image
The resulting image is the sharpened image after laplacian filtering mask is applied 5

8. 3 Step 3: 1 2 4 5 Filter mask c Instruction for the animator
Text to be displayed in the working area (DT)
The first fig. should appear and then when the radio button for third mask is selected then enable start button
After start button is clicked show the second figure
The text in DT should appear in parallel to the figures
The blurred image
The resulting image is the sharpened image after laplacian filtering mask is applied 5

9. Test your understanding
Electrical Engineering
Slide 1
Slide 3
Slide
10, 11,12
Slide 13
Introduction
Definitions
Analogy
Test your understanding
(questionnaire)‏
Lets Sum up (summary)‏
Want to know more…
(Further Reading)‏
Interactivity:
Try it yourself
Select any one of the figures
a b
c d
Select the filter size 9
Credits 9

10. Questionnaire 1
1.What is the value of the yellow box after Laplacian filter mask is applied?
Answers: a) b) c) 1 d)‏ 9 2 3 4 5

11. Questionnaire 1 2.
What are the values of yellow boxes after Laplacian filter mask is applied?
Answers: a) b) 2 3 4 5

12. Questionnaire 1 2.
What are the values of yellow boxes after Laplacian filter mask is applied?
Answers: c) d) 2 3 4 5

13. Links for further reading
Reference websites:
Books:
Digital Image Processing-
Rafael C. Gonzalez, Richard E. Woods, second edition, Pearson Education
Research papers: