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I have a bit of a problem when trying to use Aruco on Raspberry Pi 3.
I am using Python 3.5 on headless version of Raspbian and I followed this tutorial to install OpenCV with opencv_contrib - which as far as I understand contains all the packages:

https://www.pyimagesearch.com/2015/07/27/installing-opencv-3-0-for-both-python-2-7-and-python-3-on-your-raspberry-pi-2/

OpenCV installed without any problems, I can import it in Python and it works fine. I need to use Aruco for a project and when I try to import it I get this error: 

Traceback (most recent call last):
  File "<stdin>", line1, in <module>
ImportError: No module named 'cv2.aruco': 'cv2' is not a package

I had the same problem before so I flashed SD card and started with fresh installation, but it happens again. From the previous question I found here I tried to install opencv_contrib by using 

pip install opencv-contrib-python

But I got the error: 

Could not find a version that satisfies the requirement opencv-contrib-python (from versions: )  
No matching distribution found for opencv-contrib-python

Did anybody encounter the same issue, or do you have any suggestions or how to fix that? Any help would be appreciated.

Irek
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  • Any chance you named a file `cv2.py`? – Klaus D. Oct 10 '18 at 09:21
  • @KlausD. Nope, it's named cv2.so. I mean, when I copied the file from site-packages to the virtual environment – Irek Oct 10 '18 at 09:25
  • How did you do that? – Klaus D. Oct 10 '18 at 09:35
  • @KlausD. After I installed and compiled OpenCV I used "ls -l /usr/local/lib/python3.2/site-packages" to find out what's the name of Python bindings file. Then I CD into the same folder but on virtual environment and I copied that folder chaning it's name to cv2.so - as it was explained in the tutorial I was following (I included the link in the post) – Irek Oct 10 '18 at 09:43
  • That is not the standard way to install dependencies. Is there any reason you do not use `pip`? – Klaus D. Oct 10 '18 at 13:44
  • @KlausD. I tried the pip install opencv-contrib-python command, but I got an error as explained in my main post. I assume this is what you are asking about. In general, I cloned both OpenCV and OpenCV_Contrib to my Pi and I used cmake for the installation. In the cmake command I included the path for the extra modules - opencv_contrib, but I'm guessing they don't link properly with OpenCV - I can use OpenCV, but not any modules from opencv_contrib. – Irek Oct 10 '18 at 15:02

2 Answers2

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EDIT: I found the perfect solution for the problem with installing additional modules for OpenCV. Previous solution required the manual copying of files from one github directory into another, and copied files had to be added manually into the txt file. This solution allows you to install all the modules without any copying etc. I am leaving my initial thoughts in the answer as they were, the only thing that is changing are the steps to follow. Please correct me if I did anything wrong in regards to editing, as I never had to edit my own answer before due to finding a better solution (as you may see, I'm quite new in here).

I managed to solve my problem and thought I will share my solution as a new answer, so it's easier for people to see, should anyone encounter the same problem in the future.
The solution works fine when there is only need to install few modules from opencv_contrib as it requires some copying.

The overall installation process requires following this tutorial https://www.pyimagesearch.com/2015/07/27/installing-opencv-3-0-for-both-python-2-7-and-python-3-on-your-raspberry-pi-2/

New process, after finding better solution:

  1. Clone both OpenCV and OpenCV_contrib from GitHub

  2. Use cmake command from the tutorial listed above to create installation files for OpenCV. My command looked like this:

    cmake -D CMAKE_BUILD_TYPE=RELEASE \ -D CMAKE_INSTALL_PREFIX=/usr/local \ -D INSTALL_C_EXAMPLES=ON \ -D INSTALL_PYTHON_EXAMPLES=ON \ -D OPENCV_EXTRA_MODULES_PATH=~/opencv_contrib/modules \ -D BUILD_EXAMPLES=ON ..

  3. Once this command is completed and you get no errors, run cmake -D OPENCV_EXTRA_MODULES_PATH=~/opencv_contrib/modules .. again
  4. This should also work without any errors, and to double check if all the modules are going to install just scroll up the output result and you should see the line "Modules to install: " and there should be list of all modules included in opencv_contrib/modules.
  5. Once that is done and you confirmed it will install all you want/need, you can carry on with the tutorial by doing make -j4.

I know it's simply duplicating a line that was included in cmake before and I have no clue why it works after using this command again. If someone could explain why that happens, I would appreciate it and it would give me some understanding as to why it works. Again, I hope this answer helps anyone who goes through the same problem. Also, I'm sorry for editing this post twice, I thought it will be useful to show people more correct way of sorting this problem out.

Irek
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I followed the answer by Irek and have only some minor tweaks, I skipped step 3 and it worked fine, actually trying to do step 3 and I ran into issues. Also, after step 2 I run make && make install instead of step 5. I am running this in a dockerfile building on an Ubuntu 20.04 image.

tbob
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  • Your answer could be improved with additional supporting information. Please [edit] to add further details, such as citations or documentation, so that others can confirm that your answer is correct. You can find more information on how to write good answers [in the help center](/help/how-to-answer). – Community Sep 28 '21 at 16:04
  • Just wanted to add an update here. Now since some later versions of opencv, when I do this my code no longer works, it builds but when I run my python code I get "no module named cv2". I have since left this company (where I wrote this code) so not sure how that was solved. – tbob Mar 03 '22 at 15:17