問題：在用python3使用sift = cv2.SIFT()進行SIFT時候，可能會產生錯誤：AttributeError: module 'cv2' has no attribute 'SIFT'

import numpy as np
import cv2
from matplotlib import pyplot as plt
img1 = cv2.imread('data/queryImage.jpg', 0)  # queryImage
img2 = cv2.imread('data/trainImage.jpg', 0)  # trainImage
# Initiate SIFT detector
sift = cv2.SIFT()
# find the keypoints and descriptors with SIFT
kp1, des1 = sift.detectAndCompute(img1, None)
kp2, des2 = sift.detectAndCompute(img2, None)
 

報錯資訊： AttributeError Traceback (most recent call last) <ipython-input-38-d0b969ce1567> in <module>() 5 img2 = cv2.imread('data/trainImage.jpg', 0) # trainImage 6 # Initiate SIFT detector ----> 7 sift = cv2.SIFT() 8 # find the keypoints and descriptors with SIFT 9 kp1, des1 = sift.detectAndCompute(img1, None) AttributeError: module 'cv2' has no attribute 'SIFT'

解決：將sift = cv2.SIFT()替換為：sift = cv2.xfeatures2d.SIFT_create()

分析：opencv將SIFT等演算法整合到xfeatures2d集合裡面了。寫法：sift = cv2.xfeatures2d.SIFT_create()

變更樣例：

import numpy as np
import cv2
from matplotlib import pyplot as plt
img1 = cv2.imread('data/queryImage.jpg', 0)  # queryImage
img2 = cv2.imread('data/trainImage.jpg', 0)  # trainImage
# Initiate SIFT detector
#sift = cv2.SIFT()  將sift = cv2.SIFT()替換為：sift = cv2.xfeatures2d.SIFT_create()
sift = cv2.xfeatures2d.SIFT_create()
# find the keypoints and descriptors with SIFT
kp1, des1 = sift.detectAndCompute(img1, None)
kp2, des2 = sift.detectAndCompute(img2, None)
 

說明：問題產生的環境
  Python版本：3.6.5
  OpenCV版本：3.4.2