Editing Edge detection (section)

== Edge properties ==

The edges extracted from a two-dimensional image of a three-dimensional scene can be classified as either viewpoint dependent or viewpoint independent.
A ''viewpoint independent edge'' typically reflects inherent properties of the three-dimensional objects, such as surface markings and surface shape.
A ''viewpoint dependent edge'' may change as the viewpoint changes, and typically reflects the geometry of the scene, such as objects occluding one another.

A typical edge might for instance be the border between a block of red color and a block of yellow. In contrast a '''[[line (mathematics)|line]]''' (as can be extracted by a [[ridge detection|ridge detector]]) can be a small number of [[pixel]]s of a different color on an otherwise unchanging background. For a line, there may therefore usually be one edge on each side of the line.