1. A pattern recognition apparatus, comprising: (a) means for identifying an object region of an object from input image data; (b) means for extracting outline pixels of the identified object region; (c) means for polygonally-approximating an outline of said object region based on a positional relationship of the extracted outline pixels and for determining vertex coordinates of a polygonal approximation of the outline of the identified object region; said vertex coordinate determination means including: a polygonal approximation data memory for storing pixel pattern data which can be approximated as lines of a polygonal approximation of the outline from the input image data; means for determining end points of segments of the outline by referring to the pixel pattern data stored in said polygonal approximation data memory based on connectivity among the extracted outline pixels, and for sequentially segmenting said outline into the segments; and a vertex data memory for storing data about the end points of the segments to provide end point data as the polygonally-approximated vertex coordinates; (d) means for determining characteristic data representing the center and the orientation of said polygonally-approximated region based on said vertex coordinates; and (e) means for superimposing a polygonally-approximated region pattern on a dictionary pattern based on said characteristic data to generate a common region by matching the center of said polygonally-approximated region pattern with the center of said dictionary pattern and transforming the vertex coordinates of said polygonally-aproximated region pattern on the basis of any angular difference between the orientation of the polygonally approximated region pattern and orientation of said dictionary pattern to provide a transformed region pattern, and for determining a degree of matching between the transformed region pattern and the dictionary pattern.