20_discontinuity

20_discontinuity - Detection of Discontinuities COMP344...

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Detection of Discontinuities COMP344 COMP344 Detection of Discontinuities
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Image Segmentation Segmentation subdivides an image into its constituent regions or objects COMP344 Detection of Discontinuities
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Image Segmentation... Segmentation accuracy determines the eventual success or failure of computerized analysis procedures In general, image segmentation algorithms are based on 1 discontinuity in intensity value (sudden/abrupt change of intensity values), e.g. edges 2 similarity in intensity value, e.g. regions COMP344 Detection of Discontinuities
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Detection of Discontinuities There are three different types of discontinuities in a digital image 1 point 2 line 3 edge Discontinuity is detected based on the mask response, R , in a pre-defined window R = 9 i =1 w i z i z i : intensity values COMP344 Detection of Discontinuities
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Point Detection An isolated point is detected if it is different from its surroundings If | R | ≥ T ( T is a non-negative threshold), then a point has been detected at the location on which the mask is centered COMP344 Detection of Discontinuities
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Line Detection Line masks in 4 different specific directions A line is detected when the response of line mask is greater than some threshold To detect line in a specified direction use the mask associated with that direction threshold its output COMP344 Detection of Discontinuities
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Example If 4 line masks are used, then the final response is equal to largest response among the masks R = max( R horizontal , R 45 , R vertical , R - 45 ) COMP344 Detection of Discontinuities
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Edge Detection Edge is the boundary of surfaces/regions “thickness” of the edge is determined by length of the ramp slope of the ramp is inversely proportional to the degree of blurring in the edge COMP344 Detection of Discontinuities
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