Image converter and image converting method

Abstract

On conversion of a distorted circular image photographed by use of a fisheye lens to a planar regular image, parameter setting is performed by a user's intuitive manipulation to relieve the operation load. A dome-shaped virtual sphere H is defined on a distorted circular image S on the XY plane, and a user is allowed to designate a cut-out center point P (x, y) and an auxiliary point Q (x, y) on the distorted circular image S. An intersecting point G (x, y, z) immediately above the point P is determined, and a UV plane is defined on a tangent plane Swith respect to the virtual sphere H. An angle φ formed between the U axis and the X axis is determined on the basis of an angle θ formed between a reference straight line J passing through two points P, Q and the X axis. Transformation equations based on the orthogonal projection method including the coordinate values x, y, zand the angle φ as parameters are utilized to allow the coordinates (u, v) to correspond to coordinates (x, y), a distance between the two points P, Q is given as a conversion magnification m, thereby a part in the vicinity of the point P of the distorted circular image S is converted to a plane regular image on the UV plane.