1. Perspective Map
An introduction to the camera vision.
Fig 1-3.Presents how the perspective map is created from a still iamge. A reference person (a) at the front of a walkway and (b) at the end, and (c) which scales pixels by their relative size in the 3D scene.
The extraction of features from crowd segments should take into account the effects of perspective. Because objects closer to the camera appear larger, any pixels associated with a close foreground object account for a smaller portion of it than those of an object farther away. This can be compensated by normalizing for perspective during feature extraction (e.g., when computing the segment area). Each pixel is weighted according to a perspective normalization map, which is based on the expected depth of the object that generated the pixel. Pixel weights encode the relative size of an object at different depths, with larger weights given to far objects.