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classes. Shape classes should emphasize shape differences among classes, while the
shape variations within classes should not be reflected in the shape class description.
• Region identification
Region identification assigns unique labels to image regions
If non-repeating ordered numerical labels are used, the largest integer label gives the
number of regions in the image. Faculty of Engineering Robotics Technology MECH 4041 29
B.Eng (Hons.) Mechatronics S. Venkannah •
• • • • •
• Mechanical and Production Engineering Department Contour based shape descriptors
Chain codes describe an object by a sequence of unit size line segments with a given
orientation, called Freeman’s code
Simple geometric border representations are based on geometric properties of described
o Boundary length
o Bending energy
o Chord distribution
Fourier shape descriptors can be applied to closed curves, co-ordinates of which can be
treated as periodic signals.
Shape can be represented as a sequence of segments with specified properties. If the
segment type is known for all segments, the boundary can be described as a chain of
segment types, a code word consisting of representatives of a type of alphabet.
B-splines are piecewise polynomial curves whose shape is closely related to their control
polygon- a chain of vertices giving a polygonal representation of a curve. B-splines of
third order are most common, representing the lowest order which includes the change of
Shape invariants represent properties of geometric configurations that remain unchanged
under an appropriate class of transforms; machine vision is especially concerned with the
class of projective transforms.
Region based shape descriptors.
Simple geometric region descriptors use geometric properties of described regions:
o Euler’s number
o Height, width
Statistical moments interpret a normalized gray-level image function as a pro...
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This document was uploaded on 03/12/2014 for the course MECHANICAL 214 at University of Manchester.
- Spring '14