public Mat Crop()
{
using (CroppingWindow = new OpenCvSharp.Window("Cropper", WindowMode.FullScreen, srcImage))
{
CvMouseCallback onMouse = new CvMouseCallback(mouseCallback);
CroppingWindow.SetMouseCallback(onMouse);
CvTrackbarCallback2 onZoom = new CvTrackbarCallback2(trackbarCallback);
CvTrackbar zoom = CroppingWindow.CreateTrackbar2("Zoom", 100, 200, onZoom, null);
Cv2.WaitKey();
// This line is very important
// OpenCV is written in C++, which means it's unmanaged.
// So when a delegate callback variable is passed to it as a function point,
// GC in C# can no longer identify the life cycle of this delegate variable
// It's our reponsebility to make sure GC in C# will not collect it when it's still in use.
// Otherwise an exception will be thrown.
GC.KeepAlive(onMouse);
}
// seems that srcImage will be released by GC, so I must return a copy of it
return(srcImage.Clone());
}
