Method for automatic recognition of a concavity or convexity

An automatic recognition method, comprising the steps of:

• converting a photographic image of an object having at least one concavity or convexity defined therein into data in a specified feature space;
• extracting elementary areas from the converted image data in the feature space;
• obtaining a plurality of points that exist outside a virtual circle determined by a virtual center of the concavity or convexity in each extracted elementary area;
• obtaining the equation of a plane that passes through the plurality of points;
• detecting symmetric pairs of pixels in each elementary area, a symmetric pair of pixels being defined as two pixels the vectors and positions of which are symmetric with respect to the corresponding virtual concavity or convexity center;
• and
• regarding the virtual concavity or convexity center of at least one elementary area as the true center of said at least one concavity or convexity, provided that the number of symmetric pairs of pixels in the elementary area that satisfy the equation of the plane is no less than a specified number, and recognizing the position of the concavity or convexity of the object with said true center.