Unformatted text preview: Only the mixed nodes in a quad tree have children. The full nodes and empty
nodes are leaf nodes. Larger number of levels are required to produce a reasonably smoothly
curved boundary. Quad trees have been used to represent map regions in geographic information
Draw the quad tree represention of the region shown in Fig Qu. 2 below. Fig Qu. 2
2.5 Property tables.
Property table is the representation of a region by its extracted properties rather than by its
pixels. It is a table in the relational database sense that has a row for each region in the image
and a column for each property of interest. Properties can represent the size, shape, intensity,
color, or texture of the region. For example, in content based image retrieval system, regions
might be described by area, ratio of minor-to-major axis of the best fitting ellipse, two main
colors, and one or more texture measures.
Simple geometric border representation.
Boundary length – boundary length is an elementary region property, that is simply
derived from the chain code representation. Vertical and horizontal steps have unit
length, and the length of diagonal steps in 8-connectivity is √2. it can be shown that the
boundary is longer in 4-connectivity, where a diagonal step consists of two rectangular
steps with a total length of 2. a closed boundary length (perimeter) can also be easily
evaluated from the run length or quadtree representations. Boundary length increases as
the image raster resolution increases; on the other hand, region area is not affected by
higher resolution and converges to some limit.
Curvature- in the continuous case, curvature is defined as the rate of change of slope. In
discrete space, the curvature description must be slightly modified to overcome
difficulties resulting from violation of curve smoothness. The curvature scalar descriptor
finds the ratio between the total number of boundary pixels and the number of boundary
pixels where the boundary direction changes significan...
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