0 down vote favorite I have an NSView to draw a rectangle to crop image, and one NSImageView to be webcam (camera preview window). I want to put the NSView on the NSImageView. When I take a picture, it can produce a cropped image automatically. The problem is that when I don't start the camera preview window, the crop rectangle can drag and resize normally, but when I start the camera preview window, the crop rectangle out of control. I've implemented drag and resize function by mouse event. How can I resolve this problem? My code and program video: code: http://gist.github.com/536831 video: http://www.youtube.com/watch?v=DLjuBGHh3f8 Thanks!!