Installing OpenCv on the Pi3 with python3 (and usb webcam)


computer vision raspberry pi

Abdur-Rahmaan Janhangeer

Chef


opencv is one of the most difficult python package to install. it’s not a pip install easy package issue. in this post, we’ll see how to painlessly install it. Target Os =========

we are using noobs see here Target Pi =========

pi3 Existing Instructions =====================

there are two posts which i found to be nice :

[pyimagesearch] and [manmade2.com]

this tutorial is an explanationless one, refer to these two for explanations pyimagesearch notes

pyimagesearch is the reference post, however, here are some notes: 1. you don’t need to expand the filesystem if you are using noobs (the beginner setup) 2. misses qt packages 3. misses python path in ~/.profile 4. uses weird way to modify ~/.profile 5. uses multi-core compiling 6. no working script to test

manmade2.com notes

  1. included wrong make command and reinstall instructions (what if a confused user compiles open cv twice (brr))
  2. missed qt packages install
  3. misses python path in ~/.profile

Install instructions

the install process can be divided into these parts 1. install raspbian packages including the qt one 2. unzip cv sources 3. setup pip and virtual env 4. compile cv 5. fix rename bug 6. verify installation 7. test snippet

install raspbian packages including the qt one

sudo apt-get update
sudo apt-get upgrade
sudo rpi-update

sudo reboot

sudo apt-get install build-essential git cmake pkg-config
sudo apt-get install libjpeg-dev libtiff5-dev libjasper-dev libpng12-dev

sudo apt-get install libavcodec-dev libavformat-dev libswscale-dev libv4l-dev
sudo apt-get install libxvidcore-dev libx264-dev

sudo apt-get install libgtk2.0-dev
sudo apt-get install libatlas-base-dev gfortran

sudo apt-get install python2.7-dev python3-dev

sudo apt install qtbase5-dev

unzip cv sources

cd ~
wget -O opencv.zip https://github.com/Itseez/opencv/archive/3.3.0.zip
unzip opencv.zip

wget -O opencv_contrib.zip https://github.com/Itseez/opencv_contrib/archive/3.3.0.zip
unzip opencv_contrib.zip

setup pip and virtual env

wget https://bootstrap.pypa.io/get-pip.py
sudo python get-pip.py

sudo pip install virtualenv virtualenvwrapper
sudo rm -rf ~/.cache/pip

find python path with

which python

open ~/.profile with

sudo nano ~/.profile

write at the end

# virtualenv and virtualenvwrapper
export VIRTUALENVWRAPPER_PYTHON=/usr/bin/python3
export WORKON_HOME=/home/pi/.virtualenvs
source /usr/local/bin/virtualenvwrapper.sh

then

source ~/.profile

mkvirtualenv cv -p python3
workon cv
pip install numpy

compile cv

workon cv

cd ~/opencv-3.3.0/
mkdir build
cd build
cmake -D CMAKE_BUILD_TYPE=RELEASE \
    -D CMAKE_INSTALL_PREFIX=/usr/local \
    -D INSTALL_C_EXAMPLES=OFF \
    -D INSTALL_PYTHON_EXAMPLES=ON \
    -D OPENCV_EXTRA_MODULES_PATH=~/opencv_contrib-3.3.0/modules \
    -D BUILD_EXAMPLES=ON ..

make

sudo make install
sudo ldconfig
ls -l /usr/local/lib/python3.5/site-packages/

fix rename bug

cd /usr/local/lib/python3.5/site-packages/

sudo mv cv2.cpython-35m-arm-linux-gnueabihf.so cv2.so

cd ~/.virtualenvs/cv/lib/python3.5/site-packages/

ln -s /usr/local/lib/python3.5/site-packages/cv2.so cv2.so

verify installation

workon cv
python3

>>> import cv2
>>> cv2.__version__

should be 3.3.0 test snippet

still inside the environment. create a new test file called cvtest.py

write in it :

import cv2
import time

class CameraInst():
        # Constructor...
        def __init__(self):
                fps        = 20.0               # Frames per second...
                resolution = (640, 480)         # Frame size/resolution...
                w = 640
                h = 480

                self.cap = cv2.VideoCapture(0)  # Capture Video...
                print("Camera warming up ...")
                time.sleep(1)

                # Define the codec and create VideoWriter object
                fourcc = cv2.VideoWriter_fourcc(*"H264")     # You also can use (*'XVID')
                self.out = cv2.VideoWriter('output.avi',fourcc, fps, (w, h))

        def captureVideo(self):
                # Capture
                self.ret, self.frame = self.cap.read()
                # Image manipulations come here...
                self.gray = cv2.cvtColor(self.frame, cv2.COLOR_BGR2GRAY)
                cv2.imshow('frame',self.gray)

        def saveVideo(self):
                # Write the frame
                self.out.write(self.frame)

        def __del__(self):
                self.cap.release()
                cv2.destroyAllWindows()
                print("Camera disabled and all output windows closed...")

def main():
        cam1 = CameraInst()

        while(True):
                # Display the resulting frames...
                cam1.captureVideo()    # Live stream of video on screen...
                cam1.saveVideo()       # Save video to file 'output.avi'...
                if cv2.waitKey(1) & 0xFF == ord('q'):
                        break

        cleanUp()

if __name__=='__main__':
        main()

run with

python3 cvtest.py

i tetsted it with a usb webcam Further notes

if you are following pyimage search, changing swap size then /etc/dphys-swapfile is a file without extentions, not  a directory

if you are getting function not implemented don’t forget sudo apt install qtbase5-dev

if you can’t open ~/.profile with nano, make sure you put sudo before i.e. sudo nano ~/.profile

if you are getting

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.

make sure you set the python path as above (the which python part)

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