Expected behaviour

Successfully install opencv-python using pip:
python3 –m pip install opencv-python

Actual behaviour

Building wheel for opencv-python (PEP 517) ... error
CMake Error: CMake was unable to find a build program corresponding to "Ninja"

Steps to reproduce

• example code

cd test_cvsource test_cv/bin/activatepython3 -m pip install opencv-python

• operating system

$ uname -aLinux raspbari3 6.1.21-v7+ #1642 SMP Mon Apr  3 17:20:52 BST 2023 armv7l GNU/LinuxOS: Raspbian GNU/Linux 11 (bullseye) armv7lHost: Raspberry Pi Zero 2 W Rev 1.0

• architecture (e.g. x86)
  armv7l

• opencv-python version
  opencv-python-4.9.0.80.tar.gz

Issue submission checklist

• This is not a generic OpenCV usage question (looking for help for coding, other usage questions, homework etc.)
• I have read the README of this repository and understand that this repository provides only an automated build toolchain for OpenCV Python packages (there is no actual OpenCV code here)
• The issue is related to the build scripts in this repository, to the pre-built binaries or is a feature request (such as "please enable this additional dependency")
• I'm using the latest version ofopencv-python but
  apt installed OpenCV version 4.5.1 with:
  sudo apt install python3-opencv

I am using a Python virtual environment with venv.

• numpy installed correctly
• Python version 3.9.2
• Ninja does not exist in the system
• Can run opencv outside of virtual environment but it is v4.5.1