Can't use SIFT in Python OpenCV v4.20

Question

I am using OpenCV v4.20 and PyCharm IDE. I want to use SIFT algorithm. But I get this error. I looked for solutions of this error on the internet but none of them did help me. Do you know the solution of this error? (With pip I can install at least 3.4.2.16 version of OpenCV)

Here is my error:

Traceback (most recent call last): File "C:/Users/HP/PycharmProjects/features/featuredetect.py", line 7, in sift = cv.xfeatures2d_SIFT.create()

cv2.error: OpenCV(4.2.0) C:\projects\opencv-python\opencv_contrib\modules\xfeatures2d\src\sift.cpp:1210: 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'

Here is my code:

import cv2 as cv

image = cv.imread("the_book_thief.jpg")
gray_image = cv.cvtColor(image,cv.COLOR_BGR2GRAY)

sift = cv.xfeatures2d_SIFT.create()
keyPoints = sift.detect(image,None)

output = cv.drawKeypoints(image,keyPoints,None)

cv.imshow("FEATURES DETECTED",output)
cv.imshow("NORMAL",image)

cv.waitKey(0)
cv.destroyAllWindows()

Answer 1

SIFT's patent has expired in last July. in versions > 4.4, the detector init command has changed to cv2.SIFT_create(). If you're not using opencv's GUI, It's recommended to install the headless version: pip install opencv-python-headless

Answer 2

Unfortunately, according to this Github issue, SIFT no longer available in opencv > 3.4.2. Since you're using OpenCV v4.2.0, it's not included even if you have installed pip install opencv-contrib-python as shown in this post. A work around is to downgrade to any previous OpenCV version that includes SIFT (I believe any version below 3.4.3). I've been successful when downgrading to v3.4.2.16.

pip install opencv-python==3.4.2.16
pip install opencv-contrib-python==3.4.2.16

---

Using your code with v3.4.2.16, SIFT seems to work

Answer 3

I had the same issue previously. I had tried all methods but finally a very simple method work for me which has already answered by many. However, there is a little change in my approach.

1. Step 1:

   Uninstall the previously install opencv library

   pip uninstall opencv-python

2. Step 2:

   Install opencv contrib library due to copyright issue. Here, we are using version 3.4.2.17

   pip install opencv-contrib-python==3.4.2.17

   opencv contrib library installation error

   The above figure shows version 3.4.2.16 not found error. Hence, I tried with version 3.4.2.17. If this version doesn't work, try other versions of 3.4.x.

3. Step 3:

   Then run the following

   import cv2 sift = cv2.xfeatures2d.SIFT_create()

That's all. It works for me. I hope it works for you as well.

Answer 4

I had the same issue, after a lot of attempts, I tried installing opencv-contrib-python several times, but it worked just today. Just to be sure I installed both opencv-python and opencv-contrib-python.

pip install opencv-python

And

pip install opencv-contrib-python 

The version that installed was 4.4.0.46 for both opencv-python and opencv-contrib-python. In case the later versions don't support it (A few of the previous versions didn't support SIFT, the one from a month ago, the latest opencv-contrib-python patch was released on Nov 2nd, 2020).