2.3.2. Flatness/Unevenness Filter (STD)

STD, as proposed in [9], extracts information from the depth map that relates to the flatness and unevenness of candidate face regions. Flat and uneven faces detected by the classifiers are then removed using the depth map and a segmentation method based on the depth map.

The filtering method is a two-step process. In Step 1, a segmentation procedure using the depth map is applied; in Step 2, the standard deviation (STD) of the pixels of the depth map that belong to the larger segment (i.e., the region obtained by the segmentaion procedure) is calculated from each face candidate region. Those regions whose STD lies outside the range of [0.01, 2.00] are rejected.
