  We present a novel freehand sketch beautification method, which takes as
input a freely drawn sketch of a man-made object and automatically beautifies
it both geometrically and structurally. Beautifying a sketch is challenging
because of its highly abstract and heavily diverse drawing manner. Existing
methods are usually confined to the distribution of their limited training
samples and thus cannot beautify freely drawn sketches with rich variations. To
address this challenge, we adopt a divide-and-combine strategy. Specifically,
we first parse an input sketch into semantic components, beautify individual
components by a learned part beautification module based on part-level implicit
manifolds, and then reassemble the beautified components through a structure
beautification module. With this strategy, our method can go beyond the
training samples and handle novel freehand sketches. We demonstrate the
effectiveness of our system with extensive experiments and a perceptive study.
