Abstract ▼ AI-Helper

One of the important computer applications is image understanding, which is a Little different from image processing. Image understanding is the explicit description of image, while image processing is the study of image to image transforms. Image understanding is the technique which is more necessa...

One of the important computer applications is image understanding, which is a Little different from image processing. Image understanding is the explicit description of image, while image processing is the study of image to image transforms. Image understanding is the technique which is more necessary to practical engineering application than image processing. The latter however is a prerequisite for the former. The image which is the substitution of an object is usually recognized by the differences in the intensity of brightness. Intensity discontinuities in an image appear to the human eyes as boundaries or edges of objects, which are the fundamentals of recognition. The edge detection is the first step to image understanding. Various methods for edge detection have been reported and are being extensively studied, Edges represented by binary value have the shape of line or curves many of which can be expressed with analytic geometry. A line has two parameters namely the slope and intercept. A circle has three parameters, center coordinate (x_(0),y_(0)) and radius, and an ellipse has five parameters center coordinate, major and minor axis, and rotation angle. A curve is expressed by parameters. Hough transform which is well known as a robust method for line detection (i.e. two parameters determination) has gradually extended it's applicaion to the detection of circle, ellipse and other curves. And yet, the usage of Hough transform as the detector of circle and ellipse has been limited by slow speed and excessive memory since the calculation and memory requirement exponentially increases as the number of parameters to be determined increases. In this study, the methods for ellipse detection are proposed to reduce calculation cost and memory requirement. In this method, 8 points are selected so that those points may be approximately evenly distributed on the ellipse, and used to determine the five parameters by the least square method. 8 points are the tangential coordinates at the direction of 0˚ 45˚ , 90˚ 135˚ . Hough transform is used to find the tangential lines in only 4 directions. Tests for some kinds of ellipses prove that remarkable reduction is achieved in calculation and memory requirement with little error increase. This is because that memory requirement is for 8 points, coefficient matrix of 3 simultaneous equations including image itself and Hough transform is carried out only for 4 directions using only a fraction of original points.

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