destroyAllWindows

destroyAllWindows is a function in OpenCV's HighGUI module that closes and destroys all windows created by imshow or namedWindow during a program's execution. It releases the GUI resources associated with those windows and removes them from the screen. The call is independent of the main application and does not terminate the process; it only affects the graphical windows.

When invoked, destroyAllWindows closes every open HighGUI window and clears the internal window registry. It is safe to call at program termination or after you have finished displaying images. After destroying windows, you can still create new ones later in the same run by calling imshow or namedWindow again; the behavior simply regenerates the windows as needed.

Usage across language bindings: In C++, the function is cv::destroyAllWindows(); In Python, the equivalent is cv2.destroyAllWindows(); Both have no parameters and return nothing (void or None).

Related functions include destroyWindow(name), which closes a specific window, and waitKey, which processes GUI events and is commonly used in conjunction with destroyAllWindows in event-driven loops.

Notes: On some builds or backends, destroying all windows may be necessary to ensure a clean exit of the GUI subsystem, especially if windows are created dynamically or in multi-window applications. If a window refuses to close, ensure there is no active loop preventing event processing or try destroying the individual window first.

See also: destroyWindow, imshow, namedWindow, waitKey, HighGUI module.