Screen filtering boundary detection for noise filtering prior to image

Abstract

A method and apparatus which allows different amounts of filtering to be applied to specific parts of a foreground image, thus minimizing visible noise in the backing area, while preserving fine detail information of foreground objects. The method and apparatus identify three areas within the foreground, namely unobscured backing (screen) area, screen to foreground subject transition area, foreground subject area. The area where full amount of filtering is desired is the backing area, including shadows. This is the area where the background image will be added, and if noise is present in this area, it will be added to the background image. The transition area from the screen to the foreground object requires variable amounts of filtering, depending on the width of the transition. For sharply focused edges and very fine detail, the transition width is very small, and any filtering applied there will cause blurring and softening of these edges and details. Therefore, no filtering is applied to those areas. For out of focus and moving objects, the transition width is large, and no foreground detail information is visible. In these areas, a variable amount of filtering is applied, based on the width of the transition. In this manner, noise in these transition areas is significantly reduced, without much noticeable change in already blurred edges. Within foreground subject areas, no filtering is applied, thus preserving the detail of the foreground subject.