Raspbian Stretch: Install OpenCV 3 + Python on your Raspberry Pi

It’s been over two years since the release of Raspbian Jessie. As of August 17th, 2017, the Raspberry Pi foundation has officially released the successor to Raspbian Jessie — Raspbian Stretch.

Just as I have done in previous blog posts, I’ll be demonstrating how to install OpenCV 3 with Python bindings on Raspbian Stretch.

If you are looking for previous installation instructions for different platforms, please consult this list:

Otherwise, let’s proceed with getting OpenCV 3 with Python bindings installed on Raspian Stretch!

The quick start video tutorial

If this is your first time installing OpenCV or you are just getting started with Linux I highly suggest that you watch the video below and follow along with me as you guide you step-by-step on how to install OpenCV 3 on your Raspberry Pi running Raspbian Stretch:

Otherwise, if you feel comfortable using the command line or if you have previous experience with Linux environments, feel free to use the text-based version of this guide below.

Assumptions

In this tutorial, I am going to assume that you already own a Raspberry Pi 3 with Raspbian Stretch installed.

If you don’t already have the Raspbian Stretch OS, you’ll need to upgrade your OS to take advantage of Raspbian Stretch’s new features.

To upgrade your Raspberry Pi 3 to Raspbian Stretch, you may download it here and follow these upgrade instructions (or these for the NOOBS route which is recommended for beginners). The former instructions take approximately 10 minutes to download via a torrent client and about 10 minutes to flash the SD card at which point you can power up and proceed to the next section.

Note: If you are upgrading your Raspberry Pi 3 from Raspbian Jessie to Raspbian Stretch, there is the potential for problems. Proceed at your own risk, and consult the Raspberry Pi forums for help.

Important: It is my recommendation that you proceed with a fresh install of Raspbian Stretch! Upgrading from Raspbian Jessie is not recommended.

Assuming that your OS is up to date, you’ll need one of the following for the remainder of this post:

  • Physical access to your Raspberry Pi 3 so that you can open up a terminal and execute commands
  • Remote access via SSH or VNC.

I’ll be doing the majority of this tutorial via SSH, but as long as you have access to a terminal, you can easily follow along.

Can’t SSH? If you see your Pi on your network, but can’t ssh to it, you may need to enable SSH. This can easily be done via the Raspberry Pi desktop preferences menu (you’ll need an HDMI cable and a keyboard/mouse) or running sudo service ssh start  from the command line of your Pi.

After you’ve changed the setting and rebooted, you can test SSH directly on the Pi with the localhost address. Open a terminal and type ssh pi@127.0.0.1  to see if it is working.

Keyboard layout giving you problems? Change your keyboard layout by going to the Raspberry Pi desktop preferences menu. I use the standard US Keyboard layout, but you’ll want to select the one appropriate for your keyboard or desire (any Dvorkac users out there?).

Installing OpenCV 3 on a Raspberry Pi 3 running Raspbian Stretch

If you’ve ever installed OpenCV on a Raspberry Pi (or any other platform before), you know that the process can be quite time consuming with many dependencies and pre-requisites that have to be installed. The goal of this tutorial is to thus guide you step-by-step through the compile and installation process.

In order to make the installation process go more smoothly, I’ve included timings for each step so you know when to take a break, grab a cup of coffee, and checkup on email while the Pi compiles OpenCV.

Let’s go ahead and get started installing OpenCV 3 on your Raspberry Pi 3 running Raspbian Stretch.

Step #1: Expand filesystem

Are you using a brand new install of Raspbian Stretch?

If so, the first thing you should do is expand your filesystem to include all available space on your micro-SD card:

And then select the “Advanced Options” menu item:

Figure 1: Select the “Advanced Options” item from the “raspi-config” menu.

Followed by selecting “Expand filesystem”:

Figure 2: Expanding the filesystem on your Raspberry Pi 3.

Once prompted, you should select the first option, “A1. Expand File System”, hit Enter on your keyboard, arrow down to the “<Finish>” button, and then reboot your Pi — you may be prompted to reboot, but if you aren’t you can execute:

After rebooting, your file system should have been expanded to include all available space on your micro-SD card. You can verify that the disk has been expanded by executing df -h and examining the output:

As you can see, my Raspbian filesystem has been expanded to include all 32GB of the micro-SD card.

However, even with my filesystem expanded, I have already used 15% of my 32GB card.

If you are using an 8GB card you may be using close to 50% of the available space, so one simple thing to do is to delete both LibreOffice and Wolfram engine to free up some space on your Pi:

After removing the Wolfram Engine and LibreOffice, you can reclaim almost 1GB!

Step #2: Install dependencies

This isn’t the first time I’ve discussed how to install OpenCV on the Raspberry Pi, so I’ll keep these instructions on the briefer side, allowing you to work through the installation process: I’ve also included the amount of time it takes to execute each command (some depend on your Internet speed) so you can plan your OpenCV + Raspberry Pi 3 install accordingly (OpenCV itself takes approximately 4 hours to compile — more on this later).

The first step is to update and upgrade any existing packages:

Timing: 2m 14s

We then need to install some developer tools, including CMake, which helps us configure the OpenCV build process:

Timing: 19s

Next, we need to install some image I/O packages that allow us to load various image file formats from disk. Examples of such file formats include JPEG, PNG, TIFF, etc.:

Timing: 21s

Just as we need image I/O packages, we also need video I/O packages. These libraries allow us to read various video file formats from disk as well as work directly with video streams:

Timing: 32s

The OpenCV library comes with a sub-module named highgui which is used to display images to our screen and build basic GUIs. In order to compile the highgui module, we need to install the GTK development library:

Timing: 1m 36s

Many operations inside of OpenCV (namely matrix operations) can be optimized further by installing a few extra dependencies:

Timing: 23s

These optimization libraries are especially important for resource constrained devices such as the Raspberry Pi.

Lastly, let’s install both the Python 2.7 and Python 3 header files so we can compile OpenCV with Python bindings:

Timing: 45s

If you’re working with a fresh install of the OS, it is possible that these versions of Python are already at the newest version (you’ll see a terminal message stating this).

If you skip this step, you may notice an error related to the Python.h header file not being found when running make to compile OpenCV.

Step #3: Download the OpenCV source code

Now that we have our dependencies installed, let’s grab the 3.3.0 archive of OpenCV from the official OpenCV repository. This version includes the dnn  module which we discussed in a previous post where we did Deep Learning with OpenCV (Note: As future versions of openCV are released, you can replace 3.3.0 with the latest version number):

Timing: 41s

We’ll want the full install of OpenCV 3 (to have access to features such as SIFT and SURF, for instance), so we also need to grab the opencv_contrib repository as well:

Timing: 37s

You might need to expand the command above using the “<=>” button during your copy and paste. The .zip in the 3.3.0.zip may appear to be cutoff in some browsers. The full URL of the OpenCV 3.3.0 archive is:

https://github.com/Itseez/opencv_contrib/archive/3.3.0.zip

Note: Make sure your opencv and opencv_contrib versions are the same (in this case, 3.3.0). If the versions numbers do not match up, then you’ll likely run into either compile-time or runtime errors.

Step #4: Python 2.7 or Python 3?

Before we can start compiling OpenCV on our Raspberry Pi 3, we first need to install pip , a Python package manager:

Timing: 33s

You may get a message that pip is already up to date when issuing these commands, but it is best not to skip this step.

If you’re a longtime PyImageSearch reader, then you’ll know that I’m a huge fan of both virtualenv and virtualenvwrapper. Installing these packages is not a requirement and you can absolutely get OpenCV installed without them, but that said, I highly recommend you install them as other existing PyImageSearch tutorials (as well as future tutorials) also leverage Python virtual environments. I’ll also be assuming that you have both virtualenv and virtualenvwrapper installed throughout the remainder of this guide.

So, given that, what’s the point of using virtualenv and virtualenvwrapper ?

First, it’s important to understand that a virtual environment is a special tool used to keep the dependencies required by different projects in separate places by creating isolated, independent Python environments for each of them.

In short, it solves the “Project X depends on version 1.x, but Project Y needs 4.x” dilemma. It also keeps your global site-packages neat, tidy, and free from clutter.

If you would like a full explanation on why Python virtual environments are good practice, absolutely give this excellent blog post on RealPython a read.

It’s standard practice in the Python community to be using virtual environments of some sort, so I highly recommend that you do the same:

Timing: 35s

Now that both virtualenv and virtualenvwrapper have been installed, we need to update our ~/.profile file to include the following lines at the bottom of the file:

In previous tutorials, I’ve recommended using your favorite terminal-based text editor such as vim , emacs , or nano to update the ~/.profile file. If you’re comfortable with these editors, go ahead and update the file to reflect the changes mentioned above.

Otherwise, you should simply use cat and output redirection to handle updating ~/.profile :

Now that we have our ~/.profile updated, we need to reload it to make sure the changes take affect. You can force a reload of your ~/.profile file by:

  1. Logging out and then logging back in.
  2. Closing a terminal instance and opening up a new one
  3. Or my personal favorite, just use the source command:

Note: I recommend running the source ~/.profile file each time you open up a new terminal to ensure your system variables have been setup correctly.

Creating your Python virtual environment

Next, let’s create the Python virtual environment that we’ll use for computer vision development:

This command will create a new Python virtual environment named cv using Python 2.7.

If you instead want to use Python 3, you’ll want to use this command instead:

Timing: 24s

Again, I can’t stress this point enough: the cv Python virtual environment is entirely independent and sequestered from the default Python version included in the download of Raspbian Stretch. Any Python packages in the global site-packages directory will not be available to the cv virtual environment. Similarly, any Python packages installed in site-packages of cv will not be available to the global install of Python. Keep this in mind when you’re working in your Python virtual environment and it will help avoid a lot of confusion and headaches.

How to check if you’re in the “cv” virtual environment

If you ever reboot your Raspberry Pi; log out and log back in; or open up a new terminal, you’ll need to use the workon command to re-access the cv virtual environment. In previous blog posts, I’ve seen readers use the mkvirtualenv command — this is entirely unneeded! The mkvirtualenv command is meant to be executed only once: to actually create the virtual environment.

After that, you can use workon and you’ll be dropped down into your virtual environment:

To validate and ensure you are in the cv virtual environment, examine your command line — if you see the text (cv) preceding your prompt, then you are in the cv virtual environment:

Figure 3: Make sure you see the “(cv)” text on your prompt, indicating that you are in the cv virtual environment.

Otherwise, if you do not see the (cv) text, then you are not in the cv virtual environment:

Figure 4: If you do not see the “(cv)” text on your prompt, then you are not in the cv virtual environment and need to run “source” and “workon” to resolve this issue.

To fix this, simply execute the source and workon commands mentioned above.

Installing NumPy on your Raspberry Pi

Assuming you’ve made it this far, you should now be in the cv virtual environment (which you should stay in for the rest of this tutorial). Our only Python dependency is NumPy, a Python package used for numerical processing:

Timing: 11m 12s

Be sure to grab a cup of coffee or go for a nice walk, the NumPy installation can take a bit of time.

Note: A question I’ve often seen is “Help, my NumPy installation has hung and it’s not installing!” Actually, it is installing, it just takes time to pull down the sources and compile. You can verify that NumPy is compiling and installing by running top . Here you’ll see that your CPU cycles are being used compiling NumPy. Be patient. The Raspberry Pi isn’t as fast as your laptop/desktop.

Step #5: Compile and Install OpenCV

We are now ready to compile and install OpenCV! Double-check that you are in the cv virtual environment by examining your prompt (you should see the (cv) text preceding it), and if not, simply execute workon :

Once you have ensured you are in the cv virtual environment, we can setup our build using CMake:

Timing: 2m 56s

Now, before we move on to the actual compilation step, make sure you examine the output of CMake!

Start by scrolling down the section titled Python 2 and Python 3 .

If you are compiling OpenCV 3 for Python 2.7, then make sure your Python 2 section includes valid paths to the Interpreter , Libraries , numpy and packages path , similar to my screenshot below:

Figure 6: Checking that Python 3 will be used when compiling OpenCV 3 for Raspbian Stretch on the Raspberry Pi 3.

Notice how the Interpreter points to our python2.7 binary located in the cv virtual environment. The numpy variable also points to the NumPy installation in the cv environment.

Similarly, if you’re compiling OpenCV for Python 3, make sure the Python 3 section looks like the figure below:

Figure 6: Checking that Python 3 will be used when compiling OpenCV 3 for Raspbian Stretch on the Raspberry Pi 3.

Again, the Interpreter points to our python3.5 binary located in the cv virtual environment while numpy points to our NumPy install.

In either case, if you do not see the cv virtual environment in these variables paths, it’s almost certainly because you are NOT in the cv virtual environment prior to running CMake!

If this is the case, access the cv virtual environment using workon cv and re-run the cmake command outlined above.

Finally, we are now ready to compile OpenCV:

Timing: 4h 0m

I was not able to successfully leverage compiling with 2 or 4 cores (the Pi 3 has 4 cores) which would significantly cut down on compile time (previous posts here on PyImageSearch demonstrate that OpenCV and be compiled in a little over 60 minutes).

I recommend you not compile with make -j2  or make -j4  as your compile will likely freeze up at 90%. I have not been able to diagnose whether this is an issue with (1) the Pi overheating, (2) a race condition with the compile, (3) the Raspbian Stretch OS, or some combination of all three. Based on all my experimentations thus far I think it’s an issue introduced with the Raspbian Stretch OS.

If you do have a compile error using -j2  or -j4 , I suggest starting the compilation over again and using only one core:

Once OpenCV 3 has finished compiling, your output should look similar to mine below:

Figure 7: Our OpenCV 3 compile on Raspbian Stretch has completed successfully.

From there, all you need to do is install OpenCV 3 on your Raspberry Pi 3:

Timing: 52s

Step #6: Finish installing OpenCV on your Pi

We’re almost done — just a few more steps to go and you’ll be ready to use your Raspberry Pi 3 with OpenCV 3 on Raspbian Stretch.

For Python 2.7:

Provided your Step #5 finished without error, OpenCV should now be installed in /usr/local/lib/python2.7/site-pacakges . You can verify this using the ls command:

Note: In some cases, OpenCV can be installed in /usr/local/lib/python2.7/dist-packages (note the dist-packages rather than site-packages ). If you do not find the cv2.so bindings in site-packages , we be sure to check dist-packages .

Our final step is to sym-link the OpenCV bindings into our cv virtual environment for Python 2.7:

For Python 3:

After running make install , your OpenCV + Python bindings should be installed in /usr/local/lib/python3.5/site-packages . Again, you can verify this with the ls command:

I honestly don’t know why, perhaps it’s a bug in the CMake script, but when compiling OpenCV 3 bindings for Python 3+, the output .so file is named cv2.cpython-35m-arm-linux-gnueabihf.so (or some variant of) rather than simply cv2.so (like in the Python 2.7 bindings).

Again, I’m not sure exactly why this happens, but it’s an easy fix. All we need to do is rename the file:

After renaming to cv2.so , we can sym-link our OpenCV bindings into the cv virtual environment for Python 3.5:

Step #7: Testing your OpenCV 3 install

Congratulations, you now have OpenCV 3 installed on your Raspberry Pi 3 running Raspbian Stretch!

But before we pop the champagne and get drunk on our victory, let’s first verify that your OpenCV installation is working properly.

Open up a new terminal, execute the source and workon commands, and then finally attempt to import the Python + OpenCV bindings:

As you can see from the screenshot of my own terminal, OpenCV 3 has been successfully installed on my Raspberry Pi 3 + Python 3.5 environment:

Figure 8: Confirming OpenCV 3 has been successfully installed on my Raspberry Pi 3 running Raspbian Stretch.

Once OpenCV has been installed, you can remove both the opencv-3.3.0 and opencv_contrib-3.3.0 directories to free up a bunch of space on your disk:

However, be cautious with this command! Make sure OpenCV has been properly installed on your system before blowing away these directories. A mistake here could cost you hours in compile time.

Troubleshooting and FAQ

Q. When I try to execute mkvirtualenv and workon , I get a “command not found error”.

A. There are three reasons why this could be happening, all of them related to Step #4:

  1. Make certain that you have installed virtualenv and virtualenvwrapper via pip . You can check this by running pip freeze and then examining the output, ensuring you see occurrences of both virtualenv and virtualenvwrapper .
  2. You might not have updated your ~/.profile correctly. Use a text editor such as nano to view your ~/.profile file and ensure that the proper export and source commands are present (again, check Step #4 for the contents that should be appended to ~/.profile .
  3. You did not source your ~/.profile after editing it, rebooting, opening a new terminal, etc. Any time you open a new terminal and want to use a virtual environment, make sure you execute source ~/.profile to load the contents — this will give you access to the mkvirtualenv and workon commands.

Q. After I open a new terminal, logout, or reboot my Pi, I cannot execute mkvirtualenv or workon .

A. See reason #3 from the previous question.

Q. When I (1) open up a Python shell that imports OpenCV or (2) execute a Python script that calls OpenCV, I get an error: ImportError: No module named cv2 .

A. Unfortunately, this error is extremely hard to diagnose, mainly because there are multiple issues that could be causing the problem. To start, make sure you are in the cv virtual environment by using workon cv . If the workon command fails, then see the first question in this FAQ. If you’re still getting an error, investigate the contents of the site-packages directory for your cv virtual environment. You can find the site-packages directory in ~/.virtualenvs/cv/lib/python2.7/site-packages/ or ~/.virtualenvs/cv/lib/python3.5/site-packages/ (depending on which Python version you used for the install). Make sure that your sym-link to the cv2.so file is valid and points to an existing file.

Q. I’m running into other errors.

A. Feel free to leave a comment and I’ll try to provide guidance; however, please understand that without physical access to your Pi it can often be hard to diagnose compile/install errors. If you’re in a rush to get OpenCV up and running on your Raspberry Pi be sure to take a look at the Quickstart Bundle and Hardcopy Bundle of my book, Practical Python and OpenCV. Both of these bundles include a Raspbian .img file with OpenCV pre-configured and pre-installed. Simply download the .img file, flash it to your Raspberry Pi, and boot! This method is by far the easiest, hassle free method to getting started with OpenCV on your Raspberry Pi.

So, what’s next?

Congrats! You have a brand new, fresh install of OpenCV on your Raspberry Pi — and I’m sure you’re just itching to leverage your Raspberry Pi to build some awesome computer vision apps.

But I’m also willing to bet that you’re just getting started learning computer vision and OpenCV, and you’re probably feeling a bit confused and overwhelmed on where exactly to start.

Personally, I’m a big fan of learning by example, so a good first step would be to read this blog post on accessing your Raspberry Pi Camera with the picamera module. This tutorial details the exact steps you need to take to (1) capture photos from the camera module and (2) access the raw video stream.

And if you’re really interested in leveling-up your computer vision skills, you should definitely check out my book, Practical Python and OpenCV + Case Studies. My book not only covers the basics of computer vision and image processing, but also teaches you how to solve real world computer vision problems including face detection in images and video streams, object tracking in video, and handwriting recognition.

raspberry_pi_in_post

All code examples covered in the book are guaranteed to run on the Raspberry Pi 2 and Pi 3 as well! Most programs will also run on the B+ and Zero models, but might be a bit slow due to the limited computing power of the B+ and Zero.

So let’s put your fresh install of OpenCV on your Raspberry Pi to good use — just click here to learn more about the real-world projects you can solve using your Raspberry Pi + Practical Python and OpenCV .

Summary

In this blog post, we learned how to upgrade your Raspberry Pi 3‘s OS to Raspbian Stretch and to install OpenCV 3 with either Python 2.7 or Python 3 bindings.

If you are running a different version of Raspbian (such as Raspbian Wheezy) or want to install a different version of OpenCV (such as OpenCV 2.4), please consult the following tutorials:

Are you looking for a project to work on with your new install of OpenCV on Raspbian Stretch? Readers have been big fans of this post on Home surveillance and motion detection with the Raspberry Pi, Python, OpenCV, and Dropbox.

But before you go…

I tend to utilize the Raspberry Pi quite a bit on this blog, so if you’re interested in learning more about the Raspberry Pi + computer vision, enter your email address in the form below to be notified when these posts go live!

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37 Responses to Raspbian Stretch: Install OpenCV 3 + Python on your Raspberry Pi

  1. Hilman September 4, 2017 at 7:22 pm #

    Adrian. I want to ask something.
    I have the Raspberry Pi 2 (and its camera module), but I just don’t know what kind of project I can do with it.
    Since I am busy, if possible, I want to make a project that can contribute the most to what I am learning right now (mainly machine learning). Do you have any idea?
    I were thinking of using it for scrapping data, but do not know where to begin. I would be very happy if you could recommend some suggestions.

    Thanks!

    • Adrian Rosebrock September 5, 2017 at 9:18 am #

      Hi Hilman — the Raspberry Pi 2 is a bit underpowered so I wouldn’t recommend training a machine learning classifier on your Pi, but I could see deploying one. Have you considered training an image classifier to recognize a particular object on your laptop/desktop and then actually running it on your Raspberry Pi?

      Also, keep in mind that all chapters inside Practical Python and OpenCV will run on the Raspberry Pi. Go through any of those chapters and you can execute the projects on the Pi (such as face detection + tracking). Those chapters make for excellent starting points for projects.

      I hope that helps!

      • Hilman September 5, 2017 at 8:59 pm #

        Ah… I forgot about that book. Will take a look at it later. Thanks!

  2. Jorge September 5, 2017 at 4:40 am #

    Great post as always.

    I wanted to share a neat little trick: You can actually enable SSH on the RPi just by placing an empty “ssh” file (case sensitive!) in the root of the sd card (once Raspbian is flashed).
    This makes running a 100% “headless” RPi possible: From there you can keep working with SSH or enable VNC and see the desktop from there.

    • Adrian Rosebrock September 5, 2017 at 9:11 am #

      Wow, that’s a neat trick! Thanks for sharing Jorge.

  3. Hidenori Kaga September 5, 2017 at 8:09 am #

    Your page has been explained in an easy-to-understand and polite manner, so it’s always helpful very much.
    I immediately installed the CV with reference to this page.
    However, Python IDLE in the program menu causes an error in importing. How can I use CV from IDLE?

    • Adrian Rosebrock September 5, 2017 at 9:10 am #

      Hi Hidenori — as far as I understand, the GUI version of Python IDLE does not support virtual environments, thus you cannot use it. I would suggest you use IDLE via the command line (so you can access the Python virtual environment) or use Jupyter Notebooks. I hope that helps!

  4. Steve Nicholson September 5, 2017 at 3:26 pm #

    If you aren’t going to run the tests, you can save a fair amount of compile time by not including them. To do that, add “-D BUILD_TESTS=OFF” and “-D BUILD_PERF_TESTS=OFF” to the CMake command line.

  5. Abkul Orto September 6, 2017 at 6:41 am #

    Great tutorial.

    All your ” Quickstart Bundle and Hardcopy Bundle book, Practical Python and OpenCV” I bought are a jewel i am happy to have invested in.

    in your blog on “Drowsiness detection with OpenCV of May 8, 2017 in dlib, Facial Landmarks, Tutorials” you suggested :

    “If you intend on using a Raspberry Pi for this, I would:

    1. Use Haar cascades rather than the HOG face detector. While Haar cascades are less accurate, they are also faster.
    2. Use skip frames and only detect faces in every N frames. This will also speedup the pipeline.”

    I have Pi 3, Kindly do a tutorial with an example to implement the above options.

    • Adrian Rosebrock September 7, 2017 at 7:05 am #

      Hi Abkul — thank you for picking up a copy of Practical Python and OpenCV, I appreciate your support! And yes, I will be covering an updated drowsiness detector for the Raspberry Pi in the future. I can’t say exactly when this will be as I’m very busy finishing up the new deep learning book, but it will happen before the end of the year.

  6. Islam September 6, 2017 at 10:52 am #

    Where new blog about pixel by pixel for loops

    • Adrian Rosebrock September 7, 2017 at 7:01 am #

      I already covered the blog post you are referring to here. I’ll also be doing an updated one on OpenMP in the future.

  7. Rick Free September 6, 2017 at 1:37 pm #

    Followed step-by-step and it worked like a charm. Compile took about 4 hours, as expected. Thanks!

    • Adrian Rosebrock September 7, 2017 at 6:59 am #

      Congrats on getting OpenCV installed, Rick! Nice job.

  8. Galang Hakim September 7, 2017 at 9:18 am #

    Hi andrian

    thanks for sharing
    I have success installed opencv to raspberry pi 3
    thanks to your guidance

    but I wonder
    for compiling OpenCV 3 for Python 2.7 and python3.5
    the libraries, numpy and site packages only for phyton 3

    I tried for 3x
    the result are still same
    any idea about that ?

    • Adrian Rosebrock September 11, 2017 at 9:32 am #

      You would need to create two separate Python virtual environments. One for Python 2.7 and one for Python 3. Form there you can run CMake + make from inside each virtual environment to build OpenCV.

  9. Charles Horan September 7, 2017 at 2:13 pm #

    Worked like a charm..mind you I installed opencv3.3 rather than 3.1 … still worked great 😀

    • Adrian Rosebrock September 11, 2017 at 9:30 am #

      Congrats on getting OpenCV installed, Charles! Nice job.

  10. Larry Pechacek September 8, 2017 at 8:26 am #

    Upon following this latest tutorial The compile did hang up around 91% using 4 cores on RPi2. Following the tutorial RPi2 on Jessie however compiled on Stretch using all 4 cores without issue.

    • Adrian Rosebrock September 11, 2017 at 9:25 am #

      Thank you for sharing your experience, Larry!

  11. Andrew September 10, 2017 at 5:41 pm #

    I am following this install on a Pi 2b. If I backup the sd card – will it work on a Pi 3 ?

  12. Stephane September 12, 2017 at 3:12 am #

    Hi Adrian,

    I installed OpenCv on my raspberry pi3 (2017-08-16-raspbian-stretch) by following step by step your latest tutorial.
    The compilation went well and the result is similar to yours.

    When I launch a simple program, see what it returns me:

    (cv) pi@raspberrypi:~ $ sudo modprobe bcm2835-v4l2
    (cv) pi@raspberrypi:~ $ python script.py
    Unable to init server: Could not connect: Connection refused

    (video test:1029): Gtk-WARNING **: cannot open display:
    (cv) pi@raspberrypi:~ $

    This program works fine on my computer with Linux Mint.
    Thanks for your reply and sorry for my approximate English.

    Bonjour de France 🙂

    Stéphane.

    • Adrian Rosebrock September 12, 2017 at 7:13 am #

      How are you accessing your Raspberry Pi? Over SSH? Enable X11 forwarding when you SSH into your Pi:

      $ ssh -X pi@your_ip_address

  13. Stephane September 12, 2017 at 2:20 pm #

    Via ssh well on 🙂

    Ok I’ll try the x11 server activation

    cordially

  14. Chris September 14, 2017 at 6:24 am #

    The issue with the multi threaded build is the lack of size of the swap file. You need to increase it to something like 1GB for doing intensive builds.

  15. Michael September 14, 2017 at 4:23 pm #

    I tried serveral times and did follow your great tutorial in detail. Anyhow, I am not able to get the virtualenvwrapper working (and, due to this, I have issues later on).

    After the installation of virtualenv and virtualenvwrapper (both were successful, including the dependancies) and updating the ~/.profile file, I always get the error:

    pi@raspberrypi:~ $ source ~/.profile
    /usr/bin/python: No module named virtualenvwrapper
    virtualenvwrapper.sh: There was a problem running the initialization hooks.

    If Python could not import the module virtualenvwrapper.hook_loader,
    check that virtualenvwrapper has been installed for
    VIRTUALENVWRAPPER_PYTHON=/usr/bin/python and that PATH is
    set properly.

    I did not find any clue to overcome this problem.

    Any help is appreciated.

    • Adrian Rosebrock September 18, 2017 at 2:17 pm #

      Which Python version were you trying to install OpenCV + Python for? Python 2.7? Or Python 3?

    • Stephen Hayes September 20, 2017 at 1:50 pm #

      In setting up the ~/.profile, I had to add the line: “export VIRTUALENVWRAPPER_PYTHON=/usr/bin/python3” before “source /usr/local/bin/virtualenvwrapper.sh”. Otherwise, I got the “No module named virtualenvwrapper.hook_loader” error.

  16. Tom September 17, 2017 at 6:06 am #

    Just a word of warning: Stretch takes more space than Jessie (~4GB vs ~3GB) so to prevent OpenCV from building on a 8GB card.

    • Adrian Rosebrock September 18, 2017 at 2:09 pm #

      Thanks for sharing, Tom!

  17. Stephen Hayes September 18, 2017 at 4:16 pm #

    In setting up the ~/.profile, I had to add the line: “export VIRTUALENVWRAPPER_PYTHON=/usr/bin/python3” before “source /usr/local/bin/virtualenvwrapper.sh”. Otherwise, I got the “No module named virtualenvwrapper.hook_loader” error.

  18. Stephen Hayes September 20, 2017 at 10:18 pm #

    Another note: It is possible to run the make with 4 cores. Stretch suffers a bit from software bloat, so the 2GB of memory isn’t sufficient to compile with 4 cores. Edit /etc/dphys-swapfile
    and change CONF_SWAPSIZE to 2048 and reboot. You can then do make -j4. you also need to do the same thing to install dlib as that will also hang under stretch when it runs out of memory.

    • Adrian Rosebrock September 21, 2017 at 7:15 am #

      Great point Stephen, thank you for sharing.

  19. toukir September 22, 2017 at 2:23 am #

    why can’t I import cv2 directly from python shell? but when I go to terminal and write work on and import cv2 then it works.
    But I like to import cv2 from the script. so what can I do for that? I am using python 2.7 and pi3.
    please help me.

    • Adrian Rosebrock September 22, 2017 at 8:54 am #

      To clarify, are you trying to execute a Python script from your terminal? If so you still need to use “workon” before executing the script (workon only needs to be executed once):

  20. Syed Tauseef September 22, 2017 at 11:26 am #

    Hey Adrian Rosebrock ! Thanks for such a wonderful and simple tutorial, currently i am installing opencv (currently at installing numpy) i would like to know whether some of the open cv modules are dependent or matplotlib ? If so is it similar to installing like numpy ? with cv virtual environment “pip install matplotlib”

    • Adrian Rosebrock September 22, 2017 at 11:29 am #

      No, there are no OpenCV modules that are dependent on matplotlib. You can install it via:

      $ pip install matplotlib

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