trouble installing opencv on a mac (after opencv worked fine a few months ago)

asked 2018-12-17 07:54:11 -0500

ecjb gravatar image

updated 2018-12-17 09:28:03 -0500

(I posted the same question on stackoverflow:

I have opencv installed on my mac which was working a few months ago but doesn't work anymore.

I have the following specificities. - OpenCV: - Operating System / Platform: macOS 10.14 - Python 3.6.5

I tried to reload a python script where I used opencv. However, I got the following error message:

Traceback (most recent call last):
  File "<stdin>", line 1, in <module>
ImportError: dlopen(/anaconda3/lib/python3.6/site-packages/, 2): Library not loaded: /usr/local/opt/ilmbase/lib/libImath-2_2.12.dylib
  Referenced from: /usr/local/Cellar/opencv/3.4.1_4/lib/libopencv_imgcodecs.3.4.dylib
  Reason: image not found

I then tried to re-install opencv with the step by step explanation of this site with which I successfully installed opencv for the first time.

  1. determine which version of opencv I have on my machine

After having written cd /usr/local/Cellar/opencv and ls I get: 3.4.1_4 3.4.3 3.4.3_1. So I conclude that the latest version on my machine is 3.4.3_1 which is in /usr/local/Cellar/opencv/3.4.3_1/

  1. Determine the path for package in python

Then if i do the following $ cd /usr/local/Cellar/opencv/3.4.3_1 and $ cd lib, I get (among others): python3.7. Then I do the following: $ cd python3.7 and then $ cd site-packages and $ pwd, I get: /usr/local/Cellar/opencv/3.4.3_1/lib/python3.7/site-packages

  1. add the cv2.<version>.so to System python

I enter then python with $ python3 and get

Python 3.6.5 (v3.6.5:f59c0932b4, Mar 28 2018, 03:03:55) 
[GCC 4.2.1 (Apple Inc. build 5666) (dot 3)] on darwin
Type "help", "copyright", "credits" or "license" for more information.

Question N°1 Isn't it weird that it says version 3.6.5 and opencv seems to have a lib 3.7 (and no 3.6)

type >>> import sys and then >>> print(sys.path)and get the following list:

['', '/Library/Frameworks/Python.framework/Versions/3.6/lib/',

I then enter:

$ ln -s /usr/local/Cellar/opencv/3.4.3_1/lib/python3.7/site-packages/ /Library/Frameworks/Python.framework/Versions/3.6/lib/python3.6/site-packages/

  1. Add OpenCV to Virtualenvs

I then add the following command:

$ mkdir ~/Dev
$ cd ~/Dev
$ virtualenv -p python3 newcvtest
$ cd newcvtest
$ source bin/activate
(newcvtest) $ python --version 
Python 3.6.5
$ pip install numpy
$ cd lib/python3.6/site-packages
$ ln -s /usr/local/Cellar/opencv/3.4.3_1/lib/python3.7/site-packages/

After that the installation should be finished. However I still get the same error message

What should I do?

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For python 3 only. Always used pip3, python3

supra56 gravatar imagesupra56 ( 2018-12-17 09:21:02 -0500 )edit

thanks @supra56. I changed the tags accordingly

ecjb gravatar imageecjb ( 2018-12-17 09:29:33 -0500 )edit

One thing is install library... libImath-2_2.12.dylib. Are you on pc or raspberry pi?

supra56 gravatar imagesupra56 ( 2018-12-17 09:31:38 -0500 )edit

I'm on a mac. I found that it has probably to do with the fact that there are different version of python installed in my machine and that they have packages installed at different places. See:

ecjb gravatar imageecjb ( 2018-12-17 10:22:07 -0500 )edit