double cvGetNormalizedCentralMoment( cvMoments* moments, int x_order, int y_order );
moments：矩狀態結構指針
x_order：提取的 x 階矩, x_order >= 0.
y_order：提取的 y 階矩， y_order >= 0 且 x_order + y_order <= 3.
函式 cvGetNormalizedCentralMoment 提取歸一化中心矩：
ηx_order,y_order= μx_order,y_order/M00((y_order+x_order)/2+1)
