Convexity is one of the useful geometric properties of digital
sets in digital image processing. There are various applications which
require deforming digital convex sets while preserving their convexity. In
this poster, we consider the contraction of such digital sets by removing
digital points one by one. For this aim, we use some tools of combina-
torics on words to detect a set of removable points and to define such
convexity-preserving contraction of a digital set as an operation of re-
writing its boundary word. In order to chose one of removable points
for each contraction step, we present three geometrical strategies, which
are related to vertex angle and area changes. We also show experimental
results of applying the methods to repair some non-convex digital sets,
which are obtained by rotations of convex digital sets