Method for extracting target object in projection picture, projection interaction method and system thereof

The invention provides a method and a system for extracting a target object in a projection picture. The method comprises the steps of: obtaining a projection image of a projector, and generating a projection prediction image of the projection image, with respect to a projection surface based on a preset position conversion relationship and a pixel value conversion relationship; acquiring a display image displayed on the projection surface through a photographing device; comparing a difference between the display image and a pixel value of a pixel point at the same position of the projection prediction image, and extracting pixel points with the difference value in the display image greater than a preset threshold value so as to obtain a target object. According to the invention, the target object can be extracted from the projection picture precisely. The invention also provides a projection interaction method and system, which can efficiently improve interactive processing efficiency during the projection.