Install OpenCV 4.1.2 for Raspberry Pi 3 or 4 (Raspbian Buster)

README.md

Install OpenCV 4.1.2 on Raspbian Buster

$ chmod +x *.sh
$ ./download-opencv.sh
$ ./install-deps.sh
$ ./build-opencv.sh
$ cd ~/opencv/opencv-4.1.2/build
$ sudo make install

Check you can run test.py using both python 2 and 3 to verify that OpenCV python bindings were successfully installed

$ wget "https://upload.wikimedia.org/wikipedia/en/7/7d/Lenna_%28test_image%29.png" -O lenna.jpg
$ python2 test.py lenna.jpg
$ python3 test.py lenna.jpg

WARNING: Users of boards with 1GB of memory

Compiling is very memory intensive, you will likely need to increase your swap size. Assuming you have a reasonably large SD card (>16GB to be safe), follow the procedure below to increase your swap size from the default 100MB to 2GB

$ sudo dphys-swapfile swapoff
$ sudo sed -i 's:CONF_SWAPSIZE=.*:CONF_SWAPSIZE=2048:g' /etc/dphys-swapfile
$ sudo reboot

build-opencv.sh

#!/usr/bin/env bash
set -ex

OPENCV_VERSION=4.1.2
pushd ~/opencv/opencv-$OPENCV_VERSION
mkdir -p build
pushd build
MEM="$(free -m | awk /Mem:/'{print $2}')"  # Total memory in MB
# RPI 4 with 4GB RAM is actually 3906MB RAM after factoring in GPU RAM split.
# We're probably good to go with `-j $(nproc)` with 3GB or more RAM.
if [[ $MEM -ge 3000 ]]; then
  NUM_JOBS=$(nproc)
else
  NUM_JOBS=1 # Earlier versions of the Pi don't have sufficient RAM to support compiling with multiple jobs.
fi

# -D ENABLE_PRECOMPILED_HEADERS=OFF
# is a fix for https://github.com/opencv/opencv/issues/14868

# -D OPENCV_EXTRA_EXE_LINKER_FLAGS=-latomic
# is a fix for https://github.com/opencv/opencv/issues/15192

cmake -D CMAKE_BUILD_TYPE=RELEASE \
      -D CMAKE_INSTALL_PREFIX=/usr/local \
      -D OPENCV_EXTRA_MODULES_PATH=../../opencv_contrib-$OPENCV_VERSION/modules \
      -D OPENCV_ENABLE_NONFREE=ON \
      -D BUILD_PERF_TESTS=OFF \
      -D BUILD_TESTS=OFF \
      -D BUILD_DOCS=ON \
      -D BUILD_EXAMPLES=ON \
      -D ENABLE_PRECOMPILED_HEADERS=OFF \
      -D WITH_TBB=ON \
      -D WITH_OPENMP=ON \
      -D ENABLE_NEON=ON \
      -D ENABLE_VFPV3=ON \
      -D OPENCV_GENERATE_PKGCONFIG=YES \
      -D OPENCV_EXTRA_EXE_LINKER_FLAGS=-latomic \
      -D PYTHON3_EXECUTABLE=$(which python3) \
      -D PYTHON_EXECUTABLE=$(which python2) \
      ..
make -j "$NUM_JOBS"
popd; popd

download-opencv.sh

#!/usr/bin/env bash
set -ex

OPENCV_VERSION=4.1.2
cd ~
mkdir -p opencv && pushd opencv

wget -O "opencv-${OPENCV_VERSION}.tar.gz" "https://github.com/opencv/opencv/archive/${OPENCV_VERSION}.tar.gz"
wget -O "opencv_contrib-${OPENCV_VERSION}.tar.gz" "https://github.com/opencv/opencv_contrib/archive/${OPENCV_VERSION}.tar.gz"
tar -xvf "opencv-${OPENCV_VERSION}.tar.gz"
tar -xvf "opencv_contrib-${OPENCV_VERSION}.tar.gz"
popd

install-deps.sh

#!/usr/bin/env bash
set -ex

sudo apt-get purge -y libreoffice*
sudo apt-get clean
sudo apt-get update
sudo apt-get upgrade -y
sudo apt-get dist-upgrade -y
sudo apt-get autoremove -y
# For some reason I couldn't install libgtk2.0-dev or libgtk-3-dev without running the 
# following line
# See https://www.raspberrypi.org/forums/viewtopic.php?p=1254646#p1254665 for issue and resolution
sudo apt-get install -y devscripts debhelper cmake libldap2-dev libgtkmm-3.0-dev libarchive-dev \
                        libcurl4-openssl-dev intltool
sudo apt-get install -y build-essential cmake pkg-config libjpeg-dev libtiff5-dev libjasper-dev \
                        libavcodec-dev libavformat-dev libswscale-dev libv4l-dev \
                        libxvidcore-dev libx264-dev libgtk2.0-dev libgtk-3-dev \
                        libatlas-base-dev libblas-dev libeigen{2,3}-dev liblapack-dev \
                        gfortran \
                        python2.7-dev python3-dev python-pip python3-pip python python3
sudo pip2 install -U pip
sudo pip3 install -U pip
sudo pip2 install numpy
sudo pip3 install numpy

test.py

import numpy as np
import cv2
import sys

if len(sys.argv) < 2:
    print("USAGE: {} img-file".format(sys.argv[0]))
    sys.exit(1)

# Load an color image in grayscale
img = cv2.imread(sys.argv[1],0)
cv2.imshow('image',img)
cv2.waitKey(5000)
cv2.destroyAllWindows()