  Digital mosaics have usually used regular tiles, simulating the historical
"tessellated" mosaics. In this paper, we present a method for synthesizing
pebble mosaics, a historical mosaic style in which the tiles are rounded
pebbles. We address both the tiling problem, where pebbles are distributed over
the image plane so as to approximate the input image content, and the problem
of geometry, creating a smooth rounded shape for each pebble. We adapt SLIC,
simple linear iterative clustering, to obtain elongated tiles conforming to
image content, and smooth the resulting irregular shapes into shapes resembling
pebble cross-sections. Then, we create an interior and exterior contour for
each pebble and solve a Laplace equation over the region between them to obtain
height-field geometry. The resulting pebble set approximates the input image
while presenting full geometry that can be rendered and textured for a highly
detailed representation of a pebble mosaic.
