Figure 2.3:
The morphological grow algorithm used by
Pfinder to insure a connected foreground region
Connectivity constraints are enforced by iterative morphological ``growing'' from a single central point, to produce a single region that is guaranteed to be connected (see Fig. 2.3. The first step is to morphologically grow out a ``foreground'' region using a mixture density comprised of all of the blob classes. This defines a single connected region corresponding to all the parts of the user. Each of the individual blobs are then morphologically grown, with the constraint that they remain confined to the foreground region.
This results in a set of connected blobs that fill out the foreground region. However the boundaries between blobs can still be quite ragged due to misclassification of individual pixels in the interior of the figure. We therefore apply spatial Gaussian smoothing when determining the scene class likelihoods.