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3 The Problem Given an image and points on good edges. Find a way to connect the points on the edges.
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Interactive Heuristic Edge DetectionDouglas A. Lyon
Computer Engineering DepartmentFairfield University
[email protected], http://www.DocJava.com
Copyright 2002 © DocJava, Inc.
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Background
• Good Edge Detection is hard.
• We know a good edge when we see it!
• How do we know?
• Lets assume that we do!
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The Problem
• Given an image and points on good edges.
• Find a way to connect the points on the edges.
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Motivation
• Experts can find good edges
• Most edge detectors are not as good
• knowledge is hard to encode.
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Application
• Photo interpretation
• Path planning (source+destination)
• Medical imaging
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Approach
• Pixels=graph nodes
• mark an important edge
• Search in pixel space using a heuristic
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Assumptions
• A good edge is more important than speed
• Heuristics are available
• User is a domain expert
• Knowledge rep=heuristics+markers
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Photo Interpretation
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Echocardiogram
•3D-multi-scale analysis
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Path Plans, the idea
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Path Planning-pre proc.•UNAHE+thresh
•Dil+Skel
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Path Planning - Search
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Summary
• Heuristics+markers= knowledge
• Low-level image processing still needed
• Global optimization is not appropriate for all applications
• Sometimes we only want a single, good edge
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Future work
• Teach the edge detector– Training sets?
– Neural Nets?
– Better justification for heuristics…
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Open Questions
• Does the mind use open-loop filtering?
• Does the mind select from filter banks?
• Does the mind tune the filters?
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Gabor filter w/threshold
• The Strong edge is the wrong edge!
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Sub bands for 3x3 Robinson
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Sub Bands 7x7 Gabor
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Gabor-biologically motivated
Δθ =150
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http://www.docjava.com