opencv Study Notes (1)

1. The affine matrix computing

1) Equation Method:

　　cv2.getAffineTransform (src, dst), src and dst represent the coordinates and the coordinate transformation of the original, two-dimensional and three rows are ndarray 2 columns.

1 import cv2
2 import numpy as np
3 src = np.array([[0,0],[200,0],[0,200]],np.float32)
4 dst = np.array([[0,0],[100, 0], [0,100]], np.float32)
5 A = cv2.getAffineTransform(src, dst)
6 print(A)
7 #array([[0.5, 0. , 0. ],
8 #       [0. , 0.5, 0. ]])

2) matrix:

　　cv2.getRotationMatrix2D (center, angle, scale), center to center point coordinate transformation, scale is a scaling factor, angle of rotation is a counterclockwise angle (angle in radians, non radians).

1 import numpy as np
2 import cv2
3 A = cv2.getRotationMatrix2D((40, 50), 30, 0.5)
4 print(A.dtype)
5 #dtype('float64')
6 print(A)
7 #[[ 0.4330127   0.25       10.17949192]
8 # [-0.25        0.4330127  38.34936491]]