Database Systems - PowerPoint PPT Presentation

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Database Systems

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Kirsch Compass Mask. 8. Robinson Compass Mask. 9. Laplacian Mask. 10. FreiChen Masks. 11. FreiChen Masks. 12. FreiChen Masks. 13. FreiChen Masks ... – PowerPoint PPT presentation

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Title: Database Systems


1
Chapter 4
Edge Detection
2
Edge / Line Detection
  • Large change in image brightness over short
    spatial distance indicated the presents of an
    edge
  • Edge detection
  • Mark potential edge points
  • Merge the marks to merge and form lines
  • If a pixel has similar grey level values, its
    just an area
  • If a pixel has widely varying gray levels, then
    it might be an edge

3
Edge Detection Operator
  • Roberts Operator
  • Sobel Operator
  • Prewitt Operator
  • Kirsh Compass Mask
  • Robinson Compass Mask
  • Laplacian Operator
  • Frei-Chen Mask

4
Roberts Operator
5
Sobel Operator
6
Prewitt Operator
7
Kirsch Compass Mask
8
Robinson Compass Mask
9
Laplacian Mask
10
FreiChen Masks
11
FreiChen Masks
12
FreiChen Masks
13
FreiChen Masks
14
Result of Marksing
15
Hough Transform
  • Used to find lines
  • Line
  • a collection of edge points that are adjacent and
    have the same direction
  • Hough Transform
  • Takes edge points found by edge detector and find
    all lines on the edge points

16
Hough Transform
17
Hough Transform
18
Steps in Hough Transform Step 1
19
Steps in Hough Transform Step 2
20
Steps in Hough Transform Step 3
21
Steps in Hough Transform Step 4
  • Select a threshold value and examine the
    quantization blocks more than the threshold value
  • Look for continuity
  • Distance between the points on line
  • Line marked as output image
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