05 Edges

05 Edges - Edge Detection CS / ECE 181B Section 4.2.1...

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Unformatted text preview: Edge Detection CS / ECE 181B Section 4.2.1 Wednesday, January 20, 2010 Edge Detection CS / ECE 181B Edge detection Linear filtering Laplacian of the Gaussian filter Today Section 4.2.1 Wednesday, January 20, 2010 Edge Detection Edge detection is a local area operator that seeks to find significant, meaningful changes in image intensity (color?) that correspond to Boundaries of objects and patterns Texture Changes in object color or brightness Highlights Occlusions Etc. Wednesday, January 20, 2010 Useful Mathematics Funcs. Ramp Step Impulse Wednesday, January 20, 2010 The bad news Wednesday, January 20, 2010 The bad news Unfortunately, its very hard to tell significant edges from bogus edges! Noise is a big problem! Wednesday, January 20, 2010 The bad news Unfortunately, its very hard to tell significant edges from bogus edges! Noise is a big problem! An edge detector is basically a high-frequency filter, since sharp intensity changes are high-frequency events Wednesday, January 20, 2010 The bad news Unfortunately, its very hard to tell significant edges from bogus edges! Noise is a big problem! An edge detector is basically a high-frequency filter, since sharp intensity changes are high-frequency events But image noise is also high-frequency, so edge detectors tend to accentuate noise! Some things to do: Smooth before edge detection (hoping to get rid of noise but not edges!) Look for edges at multiple scales (pyramids!) Use an adaptive edge threshold Wednesday, January 20, 2010 Caveats In reality, low light levels and random noise lead to high fluctuations in individual pixel values, leading to bad estimations. Wednesday, January 20, 2010 Edge detection history Wednesday, January 20, 2010 Edge detection history Edge detection has a long history and a huge literature Edge modeling: Step edges, roof edges, impulse edges Biological modeling: How does human vision do it?...
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This note was uploaded on 12/29/2011 for the course ECE 181b taught by Professor Staff during the Fall '08 term at UCSB.

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05 Edges - Edge Detection CS / ECE 181B Section 4.2.1...

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