Calculating affine image transformation matrix

Law equation:
6 parameters requires three coordinates

import CV2
import numpy as np
src = np.array([[0,0],[200,0],[0,200]],np.float32)#原坐标，float
dst = np.array([[0,0],[100,0],[0,100]],np.float32)#变换后坐标float
A = cv2.getAffineTransform(src,dst)

Matrix:

CV2.getRotationMatrix2D(center,angle,scale)#中心坐标，旋转，缩放