LTB curves with Lipschitz turn are par-regular
- URL: http://arxiv.org/abs/2112.09567v1
- Date: Wed, 15 Dec 2021 10:10:07 GMT
- Title: LTB curves with Lipschitz turn are par-regular
- Abstract summary: This report defines the class of par-regular curves inside the class of locally turn-bounded curves.
We prove the converse assertion : locally turn-bounded curves with Lipschitz turn are par-regular.
- Score: 0.0
- License: http://arxiv.org/licenses/nonexclusive-distrib/1.0/
- Abstract: Preserving the topology during a digitization process is a requirement of
first importance. To this end, it is classical in Digital Geometry to assume
the shape borders to be par-regular. Par-regularity was proved to be equivalent
to having positive reach or to belong to the class C 1,1 of curves with
Lipschitz derivative. Recently, we proposed to use a larger class that
encompasses polygons with obtuse angles, the locally turn-bounded curves. The
aim of this technical report is to define the class of par-regular curves
inside the class of locally turn-bounded curves using only the notion of turn,
that is of integral curvature. To be more precise, in a previous article, we
have already proved that par-regular curves are locally turn-bounded.
Incidentally this proof lead us to show that the turn of par-regular curves is
a Lipschitz function of their length. We call the class of curves verifying
this latter property the curves with Lipschitz turn. In this technical report,
we prove the converse assertion : locally turn-bounded curves with Lipschitz
turn are par-regular. The equivalence is stated in Theorem 3.1 and the converse
assertion is proved in Lemma 3.2. In section 1, we recall the definition of
par-regularity and equivalently of sets with positive reach. In section 2, we
present the notions of curves locally turn-bounded and of curves with Lipschitz
turn. Throughout this latter section, some of intermediate steps (Lemmas 2.3
and 2.11) are proved just after the introduction of their related notions. The
last section (section 3) is dedicated to the proof of the equivalence of the
notions.
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