MATLAB — Unable to Import cv2 Library - matlab

Question

I'm a beginner at OpenCV, and trying to run an open-source program.
http://asrl.utias.utoronto.ca/code/gpusurf/index.html
I currently have the Computer Vision Toolbox OpenCV Interface 20.1.0 installed and Computer Vision Toolbox 9.2.
I cannot run this simple open-source feature matching algorithm without encountering errors.
import cv2
import matplotlib.pyplot as plt
%matplotlib inline
% read images
img1 = cv2.imread('[INSERT PATH #1]');
img2 = cv2.imread('[INSERT PATH #2]');
img1 = cv2.cvtColor(img1, cv2.COLOR_BGR2GRAY);
img2 = cv2.cvtColor(img2, cv2.COLOR_BGR2GRAY);
%sift
sift = cv2.xfeatures2d.SIFT_create();
keypoints_1, descriptors_1 = sift.detectAndCompute(img1,None);
keypoints_2, descriptors_2 = sift.detectAndCompute(img2,None);
len(keypoints_1), len(keypoints_2)
The following message is returned:
Error: File: Keypoints.m Line: 1 Column: 8
The import statement 'import cv2' cannot be found or cannot be imported. Imported names must end with '.*' or be
fully qualified.
However, when I remove Line 1, I instead get the following error.
Error: File: Keypoints.m Line: 2 Column: 8
The import statement 'import matplotlib.pyplot' cannot be found or cannot be imported. Imported names must end
with '.*' or be fully qualified.
Finally, following the error message only results in a sequence of further errors from the cv2 library. Any ideas?

Answer 1

That's because the code you've used isn't MATLAB code, it's python code.
As per the website you've linked:
From within Matlab
The parallel implementation coded in Matlab can be run by using the surf_find_keypoints() function. The output keypoints can be sorted by strength using surf_best_n_keypoints(), and plotted using surf_plot_keypoints().
Check that you've downloaded the correct files and try again.
Furthermore, the Matlab OpenCV Interface is designed to integrate C++ OpenCV code, not python. Documentations here.

Answer 2

Yes, it is correct that this is Python code. I would recommend checking your dependencies/libraries. The PyCharm IDE is what I personally use since it takes care of all the libraries easily.
If you do end up trying out PyCharm click on the red icon when hovering on CV2. It’ll then give you a prompt to download the library.
Edit:
Using Python some setup can be done. Using pip:
Install opencv-python
pip install opencv-python
Install opencv-contrib-python
pip install opencv-contrib-python
Unfortunately, there is some issue with the sift feature since by default it is excluded from newer free versions of OpenCV.
sift = cv2.xfeatures2d.SIFT_create() not working even though have contrib installed
import cv2
Image_1 = cv2.imread("Image_1.png", cv2.IMREAD_COLOR)
Image_2 = cv2.imread("Image_2.jpg", cv2.IMREAD_COLOR)
Image_1 = cv2.cvtColor(Image_1, cv2.COLOR_BGR2GRAY)
Image_2 = cv2.cvtColor(Image_2, cv2.COLOR_BGR2GRAY)
sift = cv2.SIFT_create()
keypoints_1, descriptors_1 = sift.detectAndCompute(Image_1,None)
keypoints_2, descriptors_2 = sift.detectAndCompute(Image_2,None)
len(keypoints_1), len(keypoints_2)
The error I received:
"/Users/michael/Documents/PYTHON/Test Folder/venv/bin/python" "/Users/michael/Documents/PYTHON/Test Folder/Testing.py"
Traceback (most recent call last):
File "/Users/michael/Documents/PYTHON/Test Folder/Testing.py", line 9, in <module>
sift = cv2.SIFT_create()
AttributeError: module 'cv2.cv2' has no attribute 'SIFT_create'
Process finished with exit code 1