Piecewise linear skeletonization using principal curves
Kegl, B.; Krzyzak, A.
Pattern Analysis and Machine Intelligence, IEEE Transactions on
Volume 24, Issue 1, Jan 2002 Page(s):59 - 74
Digital Object Identifier 10.1109/34.982884
Summary:Proposes an algorithm to find piecewise linear skeletons of
handwritten characters by using principal curves. The development of the
method was inspired by the apparent similarity between the definition of
principal curves (smooth curves which pass through the "middle" of a
cloud of points) and medial axes (smooth curves that run equidistantly
from the contours of a character image). The central
fitting-and-smoothing step of the algorithm is an extension of the
polygonal line algorithm, which approximates principal curves of data
sets by piecewise linear curves. The polygonal line algorithm is
extended to find principal graphs and complemented with two steps
specific to the task of skeletonization: an initialization method to
capture the approximate topology of the character, and a collection of
restructuring operations to improve the structural quality of the
skeleton produced by the initialization method. An advantage of our
approach over existing methods is that we optimize the skeleton graph by
minimizing an intuitive and explicit objective function that captures
the two competing criteria of smoothing the skeleton and fitting it
closely to the pixels of the character image. We tested the algorithm on
isolated handwritten digits and images of continuous handwriting. The
results indicated that the proposed algorithm can find a smooth medial
axis in the great majority of a wide variety of character templates and
that it substantially improves the pixel-wise skeleton obtained by
traditional thinning methods
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