This is the full setup of OpenCV for the Raspberry Pi 32-bits.
For more information see Q-engineering - Install OpenCV Raspberry Pi

You must have allocated enough memory, otherwise the compilation, unfortunately, crashes after 2 hours at 100%

# check your total memory (RAM + swap) first. You need at least a total of:
# OpenCV 4.10.0 -> 6.5 GB!
# OpenCV 4.9.0 -> 6.5 GB!
# OpenCV 4.8.0 -> 6.5 GB!
# OpenCV 4.7.0 -> 6.5 GB!
# OpenCV 4.6.0 -> 6.5 GB!
# OpenCV 4.5.5 -> 6.5 GB!
# OpenCV 4.5.0 -> 5.5 GB
# if not, enlarge your swap space as explained in the guide
$ free -m

$ wget https://github.com/Qengineering/Install-OpenCV-Raspberry-Pi-32-bits/raw/main/OpenCV-4-10-0.sh
$ sudo chmod 755 ./OpenCV-4-10-0.sh
$ ./OpenCV-4-10-0.sh

👉 Don't forget to reset your swap memory afterwards.

If you want to beautify OpenCV with the Qt5 GUI you need to

# Bookworm
- $ sudo apt-get install qtbase5-dev
# Other OS
- $ sudo apt-get install qt5-default

# in the cmake list
- Set the -D WITH_QT=**ON** \ (± line 54) in the script

before running the script on your RPi

OpenCV will be installed to the /usr/local directory, all files will be copied to following locations:

• /usr/local/bin - executable files
  
• /usr/local/lib - libraries (.so)
  
• /usr/local/lib/cmake/opencv4 - cmake package
  
• /usr/local/include/opencv4 - headers
  
• /usr/local/share/opencv4 - other files (e.g. trained cascades in XML format)