Method and apparatus for determining the boundary of an object

An apparatus for determining a boundary of an objected based on its optically captured image, comprising:

• (a) a binarizing section for converting a density data of each of a plurality of pixels forming the captured image into a binary signal;
• (b) a pixel extracting section for converting the binary signal into a neighbor pixel state value so that only the pixels located on the boundary or in the interior of the object have a value corresponding to the binary signals of the surround pixels;
• and
• (c) an edge-tracing section for obtaining a relative chain direction value for a pixel located on the boundary of the object in the image relative to the direction from which the chains has proceeded with reference to the neighbor pixel state value of the pixel obtained by conversion in the pixel extracting section, said edge-tracing section calculating an absolute chain direction value of a next chain direction on the basis of the relative chain direction value, said edge-tracing section including a neighbor pixel normalizer to normalize the neighbor pixel state value using an absolute chain direciton value of a previous chain direction, and said edge-tracing section obtaining the relative chain direction values and calculating the absolute chain direction values for each pixel located on the boundary to trace the boundary of the object.

A computer-readable recording medium containing a computer program for determining a boundary of an object based on its optically captured image, the computer program performing the functions of:

• (a) causing a computer operation to convert a density data of each of a plurality of pixels forming the captured image into a binary signal;
• (b) causing a computer operation to convert the binary signal into a neighbor pixel state value so that only the pixels locate don the boundary or in the interior of the object have a value corresponding to the binary signals of the surrounding pixels;
• (c) causing a computer operation to normalize the neighbor pixel state value by using an absolute chain direction value of a previous chain direction;
• (d) causing a computer operation to obtain a relative chain direction value for a pixel of the image which is located on the boundary of the object relative to the direction from which the chain has proceeded with reference to the neighbor pixel state value of the pixel;
• (e) causing a computer operation to calculate an absolute chain direction value of a next chain direction on the basis of the relative chain direction value;
• and
• (f) causing a computer operation to repeat the functions (c) to (e) for each pixel located on the boundary to trace the boundary of the object.