仿射变换，透视变换：二维坐标到二维坐标之间的线性变换，可用于landmark人脸矫正。

import cv2
import numpy as np
from matplotlib import pyplot as plt
 
img = cv2.imread('lena.jpg', 1)
rows,cols,channel = img.shape
 
pts1 = np.float32([[50,50],[200,50],[50,200]])
pts2 = np.float32([[10,100],[200,50],[100,250]])
 
M = cv2.getAffineTransform(pts1,pts2)
 
dst = cv2.warpAffine(img,M,(cols,rows))
 
plt.subplot(121),plt.imshow(img),plt.title('Input')
plt.subplot(122),plt.imshow(dst),plt.title('Output')
plt.show()

import cv2
import numpy as np
from matplotlib import pyplot as plt
 
img = cv2.imread('sudu.jpg', 1)
rows,cols,ch = img.shape
 
pts1 = np.float32([[56,65],[368,52],[28,387],[389,390]])
pts2 = np.float32([[0,0],[300,0],[0,300],[300,300]])
 
M = cv2.getPerspectiveTransform(pts1,pts2)
 
dst = cv2.warpPerspective(img,M,(300,300))
 
plt.subplot(121),plt.imshow(img),plt.title('Input')
plt.subplot(122),plt.imshow(dst),plt.title('Output')
plt.show()

# -*- coding: utf-8 -*-

import numpy as np
import cv2

def gen_point(event,x,y,flags,param):
    if event == cv2.EVENT_LBUTTONDBLCLK:
        print (x,y)

# img = np.zeros((512,512,3),np.uint8)
img = cv2.imread("lp.jpg")
cv2.namedWindow('image', 2)
cv2.setMouseCallback('image',gen_point)

while(1):
    cv2.imshow('image',img)
    if cv2.waitKey(20) & 0xFF == 27:
        break
cv2.destroyAllWindows()