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https://github.com/sthysel/arm-arch-opencv

Build optimized OpenCV on Arch for arm on a Raspberry Pi
https://github.com/sthysel/arm-arch-opencv

arch arm opencv

Last synced: about 2 months ago
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Build optimized OpenCV on Arch for arm on a Raspberry Pi

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README 

          
#+title: OpenCV 4.2.0 On Arch Arm for the Raspberry Pi 4 



Notes describing how to build a Pi4 optimized OpenCV 4.2.0+ on Arch for Arm on a

Raspberry Pi. Most all of the below can and may be scripted, there may be helper

scripts or playbooks later on.



* Installing Arch on the Pi4



By the way I use Arch Arm Linux on my Raspberry Pi's.



It is:

- Tight

- Arch

- Not Raspian

- Performant

- In line with all my other machine in the lab and house

- meme rich and zoomer approved



Be sure to use the correct image from [[https://archlinuxarm.org][Arch Linux Arm]], specifically [[https://archlinuxarm.org/platforms/armv8/broadcom/raspberry-pi-4][Raspberry Pi 4]]



 #+caption: Raspberry Pi 4 

 [[file:pics/image.png]]



** Install Arch on the Pi 4



   Below are lifted from the [[https://archlinuxarm.org/platforms/armv8/broadcom/raspberry-pi-4][armv8/broadcom]] page on the Arch Arm wiki



   The Raspberry Pi 4 has higher power requirements than the Raspberry

   Pi 3. A power supply rated at 3A is the official recommendation. Using an

   insufficient power supply will result in random, inexplicable errors and

   file system corruption.



   Early variants of the Raspberry Pi 4's USB Type-C power port is not compliant

   with the USB Type-C specification, and it will not be able to be powered by

   supplies that are compliant.



*** Prep SD card and install Arch

    Replace sdX in the following instructions with the device name for the SD

    card as it appears on your computer.



    Use ~lsblk~ to verify which labels belong to the target SD card:

    #+BEGIN_SRC 

    ❯ lsblk

    NAME   MAJ:MIN RM   SIZE RO TYPE MOUNTPOINT

    loop0    7:0    0 156.7M  1 loop /var/lib/snapd/snap/gnome-3-28-1804/110

    loop1    7:1    0  44.9M  1 loop /var/lib/snapd/snap/gtk-common-themes/1440

    loop2    7:2    0  54.7M  1 loop /var/lib/snapd/snap/core18/1650

    loop3    7:3    0  97.4M  1 loop /var/lib/snapd/snap/signal-desktop/277

    loop4    7:4    0  22.4M  1 loop /var/lib/snapd/snap/snapd/5754

    sda      8:0    0 931.5G  0 disk 

    ├─sda1   8:1    0   512M  0 part /efi

    ├─sda2   8:2    0    32G  0 part [SWAP]

    └─sda3   8:3    0   899G  0 part /

    sdb      8:16   0   2.7T  0 disk 

    └─sdb1   8:17   0   2.7T  0 part 

    sdc      8:32   1  29.7G  0 disk 

    ├─sdc1   8:33   1   100M  0 part /run/media/thys/7CE9-4243

    └─sdc2   8:34   1  29.6G  0 part /run/media/thys/f814e33d-4b31-4bf4-8dd8-dbff7fe0f570

    #+END_SRC



    In this case the SD card is ~sdc~



    1. Use fdisk to partition the SD card:

       ~fdisk /dev/sdX~

    2. At the fdisk prompt, delete old partitions and create a new one:

       - Type o. This will clear out any partitions on the drive.

       - Type p to list partitions. There should be no partitions left.

       - Type n, then p for primary, 1 for the first partition on the drive,

       - press ENTER to accept the default first sector, then type +100M for the last sector.

       - Type t, then c to set the first partition to type W95 FAT32 (LBA).

       - Type n, then p for primary, 2 for the second partition on the drive, and then press ENTER twice to accept the default first and last sector.

       - Write the partition table and exit by typing w.

    3. Create and mount the FAT file system:

       #+BEGIN_SRC 

       mkfs.vfat /dev/sdX1

       mkdir boot

       mount /dev/sdX1 boot

       #+END_SRC

    4. Create and mount the ext4 file system:

       #+BEGIN_SRC 

       mkfs.ext4 /dev/sdX2

       mkdir root

       mount /dev/sdX2 root

       #+END_SRC

    5. Download and extract the root file system (as root, not via sudo):

       #+BEGIN_SRC 

       wget http://os.archlinuxarm.org/os/ArchLinuxARM-rpi-4-latest.tar.gz

       bsdtar -xpf ArchLinuxARM-rpi-4-latest.tar.gz -C root

       sync

       #+END_SRC 

    6. Move boot files to the first partition:

       ~mv root/boot/* boot~

    7. Unmount the two partitions:

       ~umount boot root~

    8. Insert the SD card into the Raspberry Pi, connect ethernet, and apply 5V power.

    9. Use the serial console or SSH to the IP address given to the board by your router.

       - Login as the default user alarm with the password alarm.

       - The default root password is root.

    10. Initialize the pacman keyring and populate the Arch Linux ARM package signing keys:

        #+BEGIN_SRC 

        pacman-key --init

        pacman-key --populate archlinuxarm

        #+END_SRC



* Prepare build environment

  Install all the dependencies for the OpenCV build. I use ~yay~ to install of

  official and the aur. This is of course not a hard requirement, use any aur

  helper to install aur hosted dependencies or just install it manually.



** Install core system dependencies  

   ~pacman -S base-devel git nvim wget unzip~



** Install yay

   Using ~yay~ it does not matter if the dependencies come from core or aur.



*** clone yay from the aur

    ~git clone https://aur.archlinux.org/yay.git~ and build it ~makepkg -sir~

*** use yay to install the OpenCV dependencies

    ~yay -S pkg-config libjpeg libtiff libpng jasper ffmpeg libx264 cairo gdk-pixbuf pango gtk2 gtk-3lapack hdf5 ~



* Prepare Python virtualenv



  I like to keep virtualens in ~~/.virtualenvs~ :



  #+BEGIN_SRC 

  python -m venv ~/.virtualenvs/cv

  source ~/.virtualenvs/cv/bin/activate

  pip install "picamera[array]"

  #+END_SRC 



* Build OpenCV



** Get the source

   

   #+BEGIN_SRC 

   wget -O opencv.zip https://github.com/opencv/opencv/archive/4.2.0.zip

   unzip opencv.zip 

   mv opencv-4.2.0 opencv

   wget -O opencv_contrib.zip https://github.com/opencv/opencv_contrib/archive/4.2.0.zip

   unzip opencv_contrib.zip

   mv opencv_contrib-4.2.0 opencv_contrib

   #+END_SRC 



** prepare the build

   Set some OpenCV build flags

   #+BEGIN_SRC 

    cmake -D CMAKE_BUILD_TYPE=RELEASE \

        -D CMAKE_INSTALL_PREFIX=/usr/local \

        -D OPENCV_EXTRA_MODULES_PATH=~/opencv_contrib/modules \

        -D ENABLE_NEON=ON \

        -D ENABLE_VFPV3=ON \

        -D BUILD_TESTS=OFF \

        -D INSTALL_PYTHON_EXAMPLES=OFF \

        -D OPENCV_ENABLE_NONFREE=ON \

        -D CMAKE_SHARED_LINKER_FLAGS=-latomic \

        -D BUILD_EXAMPLES=OFF ..

    #+END_SRC



    #+BEGIN_SRC 

    chmod +x prepare.sh 

    ./prepare.sh 

    make -j4

    sudo make install

    sudo ldconfig

    #+END_SRC



    #+BEGIN_SRC 

    cd /usr/local/lib/python3.8/site-packages/cv2/python-3.8/

    sudo mv cv2.cpython-38-arm-linux-gnueabihf.so cv2.so

    cd ~/.virtualenvs/cv/lib/python3.8/site-packages/

    ln -s /usr/local/lib/python3.8/site-packages/cv2/python-3.8/cv2.so

    #+END_SRC



* Verify 



  #+BEGIN_SRC 

  (cv) [thys@pateye-1 site-packages]$ python

  Python 3.8.1 (default, Jan 25 2020, 17:00:07) 

  [GCC 9.2.0] on linux

  Type "help", "copyright", "credits" or "license" for more information.

  >>> import cv2

  >>> cv2.__version__

  '4.2.0'

  #+END_SRC



* Camera setup 

** Enable camera



   ~/boot/config.txt~ should look like below

   #+BEGIN_VERBATIM

   initramfs initramfs-linux.img followkernel

   gpu_mem=128 start_file=start_x.elf fixup_file=fixup_x.dat

   start_x=1

   #+END_VERBATIM



  Display camera footage: ~/opt/vc/bin/raspivid --fullscreen --vflip --timeout 0~