opencv camera callback class

Callback based camera class for openCV where the client registers a callback which then receives the frames at the framerate of the camera.

camera.h / camera.cpp

class Camera {
public:
	/**
	 * Callback which needs to be implemented by the client
	 **/
	struct SceneCallback {
		virtual void nextScene(const cv::Mat &mat) = 0;
	};

	/**
	 * Default constructor
	 **/
	Camera() = default;

	/**
	 * Starts the acquisition from the camera
	 * and then the callback is called at the framerate.
	 **/
	void start(int deviceID = 0, int apiID = 0);

	/**
	 * Stops the data aqusisition
	 **/
	void stop();

	/**
	 * Registers the callback which receives the
	 * frames.
	 **/
	void registerSceneCallback(SceneCallback* sc) {
		sceneCallback = sc;
	}

QT demo

Install the opencv development packages:

sudo apt install libopencv-dev

and the QT development packages:

sudo apt-get install qtbase5-dev
sudo apt-get install libqwt-qt5-dev

The demo displays the camera in a QT window and also displays the grey value of the centre pixel with a thermometer.

Notes for Bullseye RPi OS

Camera will fail to read camera inputs from a camera installed on a Raspberry Pi with a 64-bit with the Bullseye version of Raspberry Pi OS. The Camera class will still work if the legacy camera settings are enabled:

sudo raspi-config > Interface Options > Legacy Camera > Yes > Ok

and reboot as instructed.

Credits

• Ross Gardiner
• Adam Frew
• Alban Joseph
• Lewis Russell
• Bernd Porr