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USC Computer Science Technical Reports, no. 694 (1999)

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USC Computer Science Technical Reports, no. 694 (1999)

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Content Multiple Index Structures for Efficient Retrieval of 2D Objects
Cyrus Shahabi Maytham Safar Hezhi Ai
Integrated Media Systems Center
University of Southern California
Los Angeles, California 90089-0781
shahabi, safar, hezhi@usc.edu
Many traditional applications (e.g., CAD/CAM, Trade-
mark registry), and new multimedia applications (e.g.,
structured video, animation, MPEG-4 standard) require the
storage and management of large databases of 2D objects.
These object databases are then queried and searched for
different purposes. A sample query in multimedia applica-
tions might be “find all the scenes that contain a certain
object”. Therefore, one of the important functionalities re-
quired by all of these applications is the capability to find
objects in a database that match a given object.
We concentrate on whole matching queries, in which a
query object is compared with a set of objects to find the
ones that are either exactly identical or similar to the query
object. There are two obstacles for efficient execution of
whole match queries. First, the general problem of compar-
ing two 2D objects under rotation, scaling, and translation
invariance is known to be computationally expensive. Sec-
ond, the size of the databases are growing and hence a query
should be answered without accessing all the objects in the
database.
To address both obstacles, we identify a set of six fea-
tures that could be extracted from the objects Minimum
Bounding Circle (MBC). These are: the radius of MBC
( r), the coordinates of the center of MBC ( C), the set of
touch points on MBC (TP ), touch points angle sequence
(TPAS), vertex angle sequence (VAS), and the start point
of the angle sequence (SP ) (see Fig. 1). The features are
unique per object and can be utilized for both efficiently in-
dexing the objects, and expediting the comparison between
two objects.
We focus on three variations of match queries. The first
query type is exact match (EM); in which we look for ob-
jects that are exactly identical in shape. The second query
type is exact match with rotation, scaling or translation
(RST), in which we look for objects that are identical in
shape but either rotated or scaled or translated or any combi-
This research was supported in part by NASA/JPL contract nr.
961518, and unrestricted cash/equipment gifts from Intel, NCR ,and NSF
grants EEC-9529152 (IMSC ERC) and MRI-9724567.
C r
X
X
X
φ1
φ4
φ3
φ2
X
X
X
φ1 φ2
φ3
φ4
φ9
φ8
φ7
φ6 φ5
TP
TP & SP
TP
TP
φa
φb
φc
φd
TPAS VAS
Figure 1. MBC Features.
nation of the three. The third query type is similarity shape
retrieval (SIM); in which we look for objects that are sim-
ilar in shape per our definition of similarity. Our definition
of similarity depends on the difference in the VAS’s of the
objects.
For efficient retrieval of 2D objects by shape, we build
three index structures on different subsets of object’s MBC
features. The first structure, I
TP AS
, indexes the objects ac-
cording to their number of vertices ( m), number of touch
points ( n
TP
), and their TPASs. The second structure,
I
V AS
,uses VAS of the objects for indexing purpose. Fi-
nally, the third index structure, I
TPV AS
, is a hybrid of the
first two structures, where it uses the information provided
by both the vertices of the objects (VAS and m)and their
TPs. The index structures are based on multidimensional
index structures, e.g. R
?
-tree and they help in reducing the
number of false hits and guarantees no false drops. In order
to reduce and fix the dimensions of the index, (e.g., with
I
TPV AS
and I
V AS
), we only use a few coefficients of Dis-
crete Fourier Transformation-DF T of the angle sequences.
Since the index only helps in identifying a set of candi-
dates that satisfy the query, we might have false hits but no
false drops. This set is then filtered to eliminate all the false
hits by utilizing our feature-based variations of comparison
algorithms.
For future work, we intend to investigate match queries
under other transformations (e.g., shearing), support partial
match queries and 3D objects.

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Cyrus Shahabi, Maytham Safar, Hezhi Ai. "Multiple index structures for efficient retrieval of 2D objects." Computer Science Technical Reports (Los Angeles, California, USA: University of Southern California. Department of Computer Science) no. 694 (1999).

Asset Metadata

Creator Ai, Hezhi (author), Safar, Maytham (author), Shahabi, Cyrus (author)

Core Title USC Computer Science Technical Reports, no. 694 (1999)

Alternative Title Multiple index structures for efficient retrieval of 2D objects (title)

Publisher Department of Computer Science,USC Viterbi School of Engineering, University of Southern California, 3650 McClintock Avenue, Los Angeles, California, 90089, USA (publisher)

Tag OAI-PMH Harvest

Format 1 pages (extent), technical reports (aat)

Language English

Unique identifier UC16270321

Identifier 99-694 Multiple Index Structures for Efficient Retrieval of 2D Objects (filename)

Legacy Identifier usc-cstr-99-694

Format 1 pages (extent),technical reports (aat)

Rights Department of Computer Science (University of Southern California) and the author(s).

Internet Media Type application/pdf

Source 20180426-rozan-cstechreports-shoaf (batch), Computer Science Technical Report Archive (collection), University of Southern California. Department of Computer Science. Technical Reports (series)

Access Conditions The author(s) retain rights to their work according to U.S. copyright law. Electronic access is being provided by the USC Libraries, but does not grant the reader permission to use the work if the desired use is covered by copyright. It is the author, as rights holder, who must provide use permission if such use is covered by copyright.

Repository Name USC Viterbi School of Engineering Department of Computer Science

Repository Location Department of Computer Science. USC Viterbi School of Engineering. Los Angeles\, CA\, 90089

Repository Email csdept@usc.edu

Inherited Values

Title Computer Science Technical Report Archive

Coverage Temporal 1991/2017

Repository Email csdept@usc.edu

Repository Name USC Viterbi School of Engineering Department of Computer Science

Repository Location Department of Computer Science. USC Viterbi School of Engineering. Los Angeles\, CA\, 90089

Publisher Department of Computer Science,USC Viterbi School of Engineering, University of Southern California, 3650 McClintock Avenue, Los Angeles, California, 90089, USA (publisher)