21_edge linking

21_edge linking - Edge Linking COMP344 COMP344 Edge Linking...

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Unformatted text preview: Edge Linking COMP344 COMP344 Edge Linking Edge Linking Problem Edge points/pixels/segments seldom characterize an edge completely (e.g., noise, breaks in the edge from non-uniform illumination) Edge points are linked to become a boundary by using either local processing, or global processing (based on Hough transform ) COMP344 Edge Linking Local Processing Idea All edge points that are similar are linked/connected Question What is “ similar ”? COMP344 Edge Linking Defining “Similar” Gradient operator used to produce an edge pixel ∇ f ( x , y ) magnitude k∇ f k = q G 2 x + G 2 y direction α ( x , y ) = tan- 1 Gy Gx ( x , y ): current pixel coordinates; ( x , y ): neighbor pixel coordinates 1 Similar strengths of the responses of the gradient operator |k∇ f ( x , y ) k - k∇ f ( x , y ) k| ≤ E E : non-negative magnitude threshold 2 Similar directions of the gradient operators | α ( x , y )- α ( x , y ) | ≤ A A : non-negative angle threshold 3 Close distance between current and neighbor pixel points p ( x- x ) 2 + ( y- y ) 2 ≤ D D : non-negative distance threshold COMP344 Edge Linking Example COMP344 Edge Linking Global Processing Objective Assume that there are n points in an image and we want to find subsets of these points that lie on straight lines COMP344 Edge Linking Hough Transform...
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This note was uploaded on 09/24/2010 for the course COMP 344 taught by Professor Albertk.wong during the Fall '09 term at HKUST.

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21_edge linking - Edge Linking COMP344 COMP344 Edge Linking...

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