K-最近邻匹配

按书本代码运行出现错误代码：

[ INFO:0] Initialize OpenCL runtime...
OpenCV(3.4.1) Error: Assertion failed (K == 1 && update == 0 && mask.empty()) in
 cv::batchDistance, file D:\Build\OpenCV\opencv-3.4.1\modules\core\src\batch_dis
tance.cpp, line 265
Traceback (most recent call last):
  File "test_3.py", line 13, in <module>
    matches = bf.knnMatch(des1,des2,k=2)
cv2.error: OpenCV(3.4.1) D:\Build\OpenCV\opencv-3.4.1\modules\core\src\batch_dis
tance.cpp:265: error: (-215) K == 1 && update == 0 && mask.empty() in function c

v::batchDistance

更改脚本代码为：

import numpy as np
import cv2
from matplotlib import pyplot as plt


img1 = cv2.imread('logo.jpg',0)
img2 = cv2.imread('sing.jpg',0)


orb = cv2.ORB_create()
kp1,des1 = orb.detectAndCompute(img1,None)
kp2,des2 = orb.detectAndCompute(img2,None)


bf = cv2.BFMatcher(cv2.NORM_HAMMING,crossCheck=True)
matches = bf.knnMatch(des1,des2,k=1)#此处课本为2，更改为1后可运行


img3 = cv2.drawMatchesKnn(img1,kp1,img2,kp2,matches,img2,flags=2)
plt.imshow(img3)

plt.show()

参考：http://answers.opencv.org/question/42714/some-problem-about-knnmatch/