关键词: 矩, 重心, 主轴, 最小外接矩形, 叶片长宽

Abstract: Generally, leaf blade length and width are measured by the rotation method, which has to rotate a leaf repeatedly until the area of its enclosing rectangle attains the minimum value. It is time consuming during measurement. Besides, the measurement accuracy of this method is not high as leaf blades are in different shapes. Aiming at the above two points, a measurement method of leaf blade length and width based on moment is given. The barycenter of a leaf blade is calculated by using zeroth order moment and first order moment. The orientation of the blade major axis is obtained by means of first order moment and second order moment. The rotation matrix is used to get the minimum enclosing rectangle of the blade and the length and width of this rectangle act as the blade’s. Experiments have been done on 122 blade images collected and the experimental results show that the measurement accuracy of the method mentioned in this paper is 98.4% while that of the rotation method is 37.7%. During the measurement, the rotation method has to rotate a blade multiple times while the method based on moment only does it twice. Therefore, measurement time of the latter decreases by half the time of the former at least. In a word, the method based on moment wins a high accuracy and speed.

Key words: moment, barycenter, major axis, minimum enclosing rectangle, leaf blade length and width