derivate_vector_field: Convolve a vector field with derivatives of the Gaussian 用高斯导数卷积向量场
derivate_vector_field(VectorField : Result : Sigma, Component : )
derivate_vector_field convolves the components of a vector field with the derivatives of a Gaussian and calculates various features derived therefrom. derivate_vector_field only accepts vector fields of the semantic type 'vector_field_relative'. TheVectorField F(r,c)=(u(r,c),v(r,c)) is defined as in optical_flow_mg. Sigma is the parameter of the Gaussian (i.e., the amount of smoothing). If a single value is passed in Sigma, the amount of smoothing in the column and row direction is identical. If two values are passed in Sigma, the first value specifies the amount of smoothing in the column direction, while the second value specifies the amount of smoothing in the row direction. The possible values for Component are:
derivate_vector_field算子使用高斯导数卷积矢量场的成分，然后计算由此派生的各种特征。derivate_vector_field算子只接受语意类型为'vector_field_relative'的矢量场。 矢量场F(r,c)=(u(r,c),v(r,c))由算子 optical_flow_mg定义。Sigma 是高斯平滑参数，如果传入一个独立数值，列方向平滑与行方向平滑一致；如果传入两个数值，第一个是列方向平滑，第二个是行方向平滑。Component 的可选参数如下：
'curl':
The curl of the vector field. One application of using 'curl' is to analyse optical flow fields. Metaphorically speaking, the curl is how much a small boat would rotate if the vector field was a fluid.
‘curl’：矢量场的卷曲。卷曲的应用之一是分析光流场。打个比方，如果矢量场是流体，卷曲就代表小船旋转了多少。
'divergence':
The divergence of the vector field. One application of using 'divergence' is to analyze optical flow fields. Metaphorically speaking, the divergence is where the source and sink would be if the vector field was a fluid.
'divergence': 向量场的散度，散度的应用之一是分析光流场。打个比方，如果矢量场是流体，散度就代表源和汇的位置。