About homogeneous transformation

[eeyrw]

I notice that the fixed H matrix for homogeneous transformation is used:

    y_start = 0.3
    y_stop = 1
    src = np.float32([[0.45,y_start],[0.55, y_start],[0.1,y_stop],[0.9, y_stop]])
    dst = np.float32([[0.45, y_start],[0.55, y_start],[0.45, y_stop],[0.55,y_stop]])
    M_inv = cv2.getPerspectiveTransform(dst,src)

How does these parameters come from? Are these parameters empirical?