Building Computer Vision Projects with OpenCV 4 and C++

Checking and handling mouse clicks

Now that we have all our GUI elements drawn, we need to process mouse events. When we initialized the display window, we told OpenCV that we want a mouse event callback to our onMouse function.

We don't care about mouse movement, only the mouse clicks, so first we skip the mouse events that aren't for the left mouse button click as follows:

    void onMouse(int event, int x, int y, int, void*)     {       if (event != CV_EVENT_LBUTTONDOWN)         return;       Point pt = Point(x,y);       ... (handle mouse clicks)       ...     }

As we obtained the drawn rectangle bounds of the buttons when drawing them, we just check whether the mouse click location is in any of our button regions by calling OpenCV's inside() function. Now, we can check ...