Unformatted text preview: ble. Properties of this random
variable can be described using statistical characteristics- moments.
Graph representation based on region skeleton- this method corresponds significantly
curving points of a region boundary to graph nodes. The main disadvantage of boundary
based description methods is that geometrically close points can be far away from one
another when the boundary is described- graphical representation methods overcome this
disadvantage. Shape properties are then derived from the graph properties.
The region graph is based on the region skeleton, and the first step is the skeleton
construction. There are four basic approaches to skeleton construction:
Thinning – iterative removal of region boundary pixels
Wave propagation from the boundary.
Detection of local maxima in the distance-transformed image of the region
A large number of thinning algorithms exist.
Region decomposition- the decomposition approach is based on the idea that shape
recognition is a hierarchical process. Shape primitives are defined at the lower level,
primitives being the simplest elements which from the region. A graph is constructed at
the higher level- nodes result from primitives, arcs describe the mutual primitive relations. Faculty of Engineering Robotics Technology MECH 4041 28
B.Eng (Hons.) Mechatronics S. Venkannah Mechanical and Production Engineering Department Convex sets of pixels are one example of simple shape primitives. The solution to
decomposition problem consists of 2 main steps:
To segment a region into simpler sub regions (primitives)
The analysis of primitives
Primitives are simple enough to be described successfully using simple scalar shape properties.
Region neighborhood graphs- any time a region decomposition into sub-regions or an
image decomposition into regions is available, the region or image can be represented by a
region neighborhood graph. This graph represents every region as a graph node, and
nodes of neighboring regions are connected by edges...
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