  We consider the problem of segmenting dynamic regions in CrowdCam images,
where a dynamic region is the projection of a moving 3D object on the image
plane. Quite often, these regions are the most interesting parts of an image.
CrowdCam images is a set of images of the same dynamic event, captured by a
group of non-collaborating users. Almost every event of interest today is
captured this way. This new type of images raises the need to develop new
algorithms tailored specifically for it. We propose a comprehensive solution to
the problem. Our solution combines cues that are based on geometry, appearance
and proximity. First, geometric reasoning is used to produce rough score maps
that determine, for every pixel, how likely it is to be the projection of a
static or dynamic scene point. These maps are noisy because CrowdCam images are
usually few and far apart both in space and in time. Then, we use similarity in
appearance space and proximity in the image plane to encourage neighboring
pixels to be labeled similarly as either static or dynamic. We collected a new,
and challenging, data set to evaluate our algorithm. Results show that the
success score of our algorithm is nearly double that of the current state of
the art approach.
