总结:
Basic Shape features , shape context, HOG
Basic Shape features:
1) diff = object的最小多凸多边形面积 - object面积, 即下图中白色区域
2)Compatness = object面积/ 与object同周长的圆的面积
Circularity = 4Π*object面积/ 周长的平方
3)Elongation = lenght / width
Eccentricity = minor axis / major axis
Boundary Descriptors:
1) Chain code descriptor : 确定8个方向,用一串连续的数字来表示shape的走势,如2 1 0 7 7 0 1 1
2)Local curvature descriptor: 曲率(curvature)是图形的attribute,将图形每个点的curvature连在一起,可画出曲率图。凸点>0,凹点<0.
(1)Geometrical interpretation: K(s) = 1 / r(s) ; r(s)是该点处fit圆的半径,半径越大,曲率越小,所以取倒数
(2)Physical interpretation: 取每个点的导数 K(s) = dτ/ds
3) Radial distance descriptor: 所有边界上的点到中心点的距离之和,类似于方差(这个方法不是很清楚) 衡量 roughness