View
2
Download
0
Category
Preview:
Citation preview
Pattern Detection
Computer Vision
Some slides are from Yanxi Liu, CSE PennState Univ.
Correspondence Problem & Keypoint
Image Filters, Gradients, Image Processing
Blob Detectors, Edge, Corner, Key Points
Matching, Tracking, Homography
Shapes, Patterns (2D, 3D, Spatiotemporal)
Recognitions (Object, Face, Gesture, Instance, Scene)
Symmetry Pattern Detection
s
30
Four Types of Primitive Symmetries
in 2D Euclidean Space [H. Weyl, 1952]
Rotation symmetry Translation symmetry Reflection symmetry
Glide-reflection symmetry
translation reflection
Reflection Symmetry Pattern Detection
43
Curved Symmetry Axes are Everywhere!
Lizards & snakes
Leaves
Spines
44
Related Work
Medial axis detection 2
Medial axis is not designed to find
(glide) reflection symmetries of the
pattern
[Peng et. al., Bioinformatics 08]
[Bonnassie et. al., ICIP 01]
Medial axis is not designed to find a
symmetry axis given discrete subparts
45
Curved Glide-Reflection
Special cases of curved
glide-reflection symmetry
1. Reflection 2. Glide-reflection 4. Curved reflection 3. Non-Uniform
glide-reflection
Curved glide-reflection
46
Axes Grouping
46
Feature point
extraction
Matching point
pair selection
Curve fitting
Axes grouping
Axes grouping based
on the distance in 2D
density space
3D parameter
space
2d projection
Algorithm
47
Curve Fitting
47
Feature point
extraction
3D parameter
space
Axes grouping
Curve fitting -Fit 1~5 degree polynomial curves
Matching point
pair selection
Algorithm
48
Curve Fitting With RANSAC
48
Feature point
extraction
3D parameter
space
Axes grouping
Curve fitting
Matching point
pair selection
Algorithm
49
Experimental Results
49 Zebra fish
Lizard
Leaves
Spine
Caterpillar
50
Curved axis rectification
50
Curved axis detection and rectification improves classification rate.
Quercus robur
Tilia
Sorbus aucuparia
Rotation Symmetry Pattern Detection
52
Rotation Symmetry Groups
Cyclic group
Dihedral group Orthogonal group
[ 5 properties ] 1. Center of rotation
2. Affine deformation
3. Symmetry type
4. Cardinality
5. Supporting region
53
Frieze-Expansion
54
Frequency Analysis
54
RSS
Affine
rectification
SSD LF
Frequency
analysis
Frieze-expansion
Merging &
elimination
55
Experimental Results
55
Real single-center images
56
Experimental Results
56
Real multi-center images
Recommended