SIFT() in opencv is not working: 'module' object has no attribute 'SURF'

Question

I am trying to run the simplest opencv SIFT code through the shell of Ubuntu, with no luck

I get an error:

AttributeError: 'module' object has no attribute 'SURF'

The code:

import cv2
cv2.SIFT()

My configurations:

• Ubuntu version is 13.10 64bit
• cv2.__version__ is 2.4.5
• the output of dir(cv2) is (for the S letter only)

'scaleAdd', 'segmentMotion', 'sepFilter2D', 'setIdentity', 'setMouseCallback', 'setTrackbarPos', 'setUseOptimized', 'setWindowProperty', 'solve', 'solveCubic', 'solvePnP', 'solvePnPRansac', 'solvePoly', 'sort', 'sortIdx', 'split', 'sqrt', 'startWindowThread', 'stereoCalibrate', 'stereoRectify', 'stereoRectifyUncalibrated', 'subtract', 'sumElems'

Answer 1

import cv2
sift = cv2.SIFT()

This code will not work if you are using opencv version 3.0 or greater. an alternative of this code is

sift = cv2.xfeatures2d.SIFT_create()
(Only works if you have installed opencv-contrib-python library )

Now again if you have an opencv-contrib-python version > 3.4 than it won't work with a different erro

error: OpenCV(4.1.0) C:\projects\opencv-python\opencv_contrib\modules\xfeatures2d\src\sift.cpp:1207: error: (-213:The function/feature is not implemented) This algorithm is patented and is excluded in this configuration; Set OPENCV_ENABLE_NONFREE CMake option and rebuild the library in function 'cv::xfeatures2d::SIFT::create'

best solution for this is:

**step 1: pip uninstall opencv-python**

**step 2: pip install opencv-contrib-python==3.4.2.16**

This worked for me.

[Note : If you have not installed opencv using pip install opencv-python, than just go and delete the downloaded library and follow the above instruction]