水果形状的傅里叶描述子研究  

Fourier Descriptor of Fruit Shape

作　　者：应义斌[1] 

机构地区：[1]浙江大学农业工程与食品科学学院,浙江杭州310029

出　　处：《生物数学学报》2001年第2期234-240,共7页Journal of Biomathematics

基　　金：国家自然科学基金资助项目(39800099); 浙江省自然科学基金资助项目

摘　　要：水果的形状是水果分级的重要指标之一．本文研究了不规则物体形状的数学描述方法，认为在水果的分级过程中采用曲线拟合的方法来描述水果的形状是不合适的；提出了仅需利用物体的边界信息求物体的形心坐标和描述果形的新方法；发现用Ｆｏｕｒｉｅｒ描述子的前４个谐波分量的变化特性就能较好地代表水果的形状，用前１５个谐波分量来描述形状则可以达到相当高的精度．而且傅立叶描述子可以进行平移、旋转和缩放，并具有很强的水果外形重建功能，是一描述水果形状的非常有效的算法．This shpae of fruit is one of the most important features in classification. Various mathematical methods for describing the shape of irregular fruits were investigated. It was not suitable to adopt curve fitting to describe the pear shape in the course of fruit classification. The new method to calulate centroid coordinates and to describe the shape of the object only based on the boundary information was put forward. It was greatly efficient to describe the shape using Fourier descriptor, which uses boundary radius and its Fourier transform to spectrum domain. It appeared that the change patterns of first 4 harmonics were sufficient for representing the main shape features of fruit, and more accuracy in the reconstruction, especially at the calyx pole, was obtained with first 15 harmonics. Besides, they allow the reconstruction of the pear shape. Furthermore, the Fourier descriptors can made in variant to translation, rotation, and scale, this feature is very important for 'on-line' grading objectives. It was found that the identification accuracy reached 90% by applying the Fourier descriptor in combination with artificial neural networks. This method also could be used to identify the shape of other fruits if suitable training set is found.

关 键 词：傅立叶描述子 机器视觉 水果形状 曲线拟合 不规则物体形状 谐波分量 边界信息 

分 类 号：TP391.41[自动化与计算机技术—计算机应用技术] O174.22[自动化与计算机技术—计算机科学与技术]