PROBLEM TO BE SOLVED: To provide an algorithm that stably calculates an angle with a crack (hereinafter a beard) like a short beard and a crack (hereinafter a main crack) of a main line that are branched around a crack to estimate a generation history of the crack, with respect to a binary image of a crack that has been performed binarization after imaging a crack. SOLUTION: A crack shape calculating method calculates the intersecting angle of respective intersecting portions, when detecting the crack and the beards to calculates angles at respective roots of them, by pixels forming a main crack portion and a beard portion in a doughnut-like disk specified by two different radii around the intersecting point of the root. An estimating method of crack generating history estimates the generation history of the crack by the distribution of the angles obtained. COPYRIGHT: (C)2006,JPO&NCIPI
