Browsing by Author "CHOU, SL"

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DETECTION OF GENERALIZED PRINCIPAL AXES IN ROTATIONALLY SYMMETRICAL SHAPES
(1991)
TSAI, WH
;
CHOU, SL
;
資訊工程學系
;
Department of Computer Science
Automatic detection of the principal axes of given shapes with known symmetry properties is studied in this paper. The inapplicability of a well-known equation, which is used to compute the direction of the principal axis of a given shape using moment functions, to a class of so-called degenerate shapes is first pointed out. Rotationally symmetric shapes often encountered in real applications are shown to belong to this class. This problem is solved by extending the notion of principal axis to higher order ones in terms of higher order moment functions. Analytic equations for computing the direction of high-order principal axes are derived. They include the well-known equation for computing the direction of the (second-order) principal axis as a special case. Some experimental results are included finally to show the effectiveness of the derived analytic equations.
DETECTION OF ROTATIONALLY SYMMETRICAL SHAPE ORIENTATIONS BY FOLD-INVARIANT SHAPE-SPECIFIC POINTS
(1992-05-01)
LIN, JC
;
CHOU, SL
;
TSAI, WH
;
資訊工程學系
;
Department of Computer Science
Two new types of shape-specific points, called fold-invariant centroid (FIC) and fold-invariant radius weighted mean (FIRWM), are introduced for detecting the orientations of rotationally symmetric shapes. A given rotationally symmetric shape is first transformed into a new fold-invariant shape. The centroid and the radius weighted mean of the new shape are then transformed back to obtain the proposed FIC and FIRWM, respectively. FIC and FIRWM points are proved to be invariant to translation, rotation and scaling, and so can be used for matching rotationally symmetric shapes. Using the proposed fold-invariant shape-specific points to detect the orientations of rotationally symmetric shapes is easier to implement than that of using the fold principal axes. Some illustrative examples and a method to avoid the case where the proposed fold-invariant shape-specific points are too close to the centroid are also given.
FOLD PRINCIPAL AXIS - A NEW TOOL FOR DEFINING THE ORIENTATIONS OF ROTATIONALLY SYMMETRICAL SHAPES
(1991-02-01)
CHOU, SL
;
LIN, JC
;
TSAI, WH
;
資訊工程學系
;
Department of Computer Science
A new type of principal axis, namely, fold principal axis, is introduced in this paper, which can be used to define the orientations of rotationally symmetric shapes. A given shape is first transformed into a new shape on which the well-defined traditional principal axis is detected. The traditional principal axis is then transformed back to obtain the proposed fold principal axes of the given shape. The properties of such axes, including the uniqueness, existence, and invariance under rotation, translation, and scaling, are investigated. Some illustrative examples are also given.