1. An image processing method for performing segmentation on an image including an articulated object having a shape that changes, based on motions of blocks, each of the blocks being comprised of one pixel or adjacent pixels, said image processing method comprising: an image receiving step of receiving temporally successive images; a motion analyzing step of calculating the motions of the blocks using at least two temporally different images and calculating, based on the calculated motions of the blocks, temporal motion trajectories of the blocks in the temporally successive images, each of the temporal motion trajectories showing a series of positions through which a corresponding one of the blocks moves on the temporally successive images; a distance calculating step of calculating first distances based on (a) a difference of positions, (b) an angle, (c) a difference of an angle of motion or (d) a change of motion, between a temporal motion trajectory of a block i and a temporal motion trajectory of a block other than the block i calculated in said motion analyzing step, each of the calculated first distances indicating a similarity of the motions of the blocks; and a nonlinear space processing step of projecting the first distances calculated in said distance calculating step into a nonlinear space by calculating nonlinearized distances and transforming the nonlinearized distances into vectors by performing dimensionality reduction and segmentation of the vectors, wherein the nonlinearized distances are calculated by converting the first distances into geodesic distances using one of the following alternatives: (i) calculating second distances by infinitizing each of the first distances when the first distance is greater than k-th smallest of the first distances and calculating geodesic distances using the second distances; (ii) calculating the second distances by infinitizing each of the first distances when the first distance is greater than a threshold and calculating the geodesic distances using the second distances; and (iii) calculating the second distances by transforming each of the first distances using an exponential function and calculating the geodesic distances using the second distances, wherein, in said distance calculating step, using two distance functions, distances are calculated for each of pairs of the blocks, and wherein, in said nonlinear space processing step, each of the distances is transformed into vectors in respective different nonlinear spaces, and segmentation of concatenated vectors is performed which is a concatenation of two vectors of the different nonlinear spaces.