Patent ID: 7680357
Filing Date: 2010-03-16
Classification: G06K

Abstract:
1. A method of detecting a position of a center point of a circular pattern, in which a position of a center point of a circular pattern contained in a photographic image is detected from the photographic image, the method comprising the steps of: i) performing voting of coordinates of all pixels in the photographic image onto a Hough space corresponding to annuluses, which Hough space is defined by a coordinate system having an X coordinate axis for a center point of a circle, a Y coordinate axis for a center point of a circle, and an r coordinate axis for a radial direction, ii) acquiring a vote value of each of voting positions having coordinates (X, Y, r) on the Hough space from a calculation of a number of votes having been given to each of the voting positions having the coordinates (X, Y, r) on the Hough space, the thus acquired vote value being taken as a first integrated vote value, a plurality of first integrated vote values being obtained with respect to the voting positions having the coordinates (X, Y, r) on the Hough space, and iii) detecting a position, which is represented by (X, Y) coordinate values of a voting position associated with the largest first integrated vote value among the plurality of the first integrated vote values having been obtained with respect to the voting positions having the coordinates (X, Y, r) on the Hough space, as the position of the center point of the circular pattern, wherein weighted addition is performed on the number of votes having been given by all of the pixels in the photographic image, and wherein the number of a vote given by a pixel having a high chromatic color degree is assigned with a weight lighter than the weight assigned to the number of a vote given by a pixel having a low chromatic color degree, and a value having been obtained from the weighted addition is taken as the vote value.