namedWindow + opencv

namedWindow

Creates a window.

C++: void namedWindow(const string& winname, int flags=WINDOW_AUTOSIZE )

Python: cv2.namedWindow(winname[, flags]) → None

C: int cvNamedWindow(const char* name, int flags=CV_WINDOW_AUTOSIZE )

Python: cv.NamedWindow(name, flags=CV_WINDOW_AUTOSIZE) → None

Parameters:

name – Name of the window in the window caption that may be used as a window identifier. flags – Flags of the window. The supported flags are: WINDOW_NORMAL If this is set, the user can resize the window (no constraint). WINDOW_AUTOSIZE If this is set, the window size is automatically adjusted to fit the displayed image (see imshow() ), and you cannot change the window size manually. WINDOW_OPENGL If this is set, the window will be created with OpenGL support.

The function namedWindow creates a window that can be used as a placeholder for images and trackbars. Created windows are referred to by their names.

If a window with the same name already exists, the function does nothing.

You can call destroyWindow() or destroyAllWindows() to close the window and de-allocate any associated memory usage. For a simple program, you do not really have to call these functions because all the resources and windows of the application are closed automatically by the operating system upon exit.

Note

Qt backend supports additional flags:

• CV_WINDOW_NORMAL or CV_WINDOW_AUTOSIZE: CV_WINDOW_NORMAL enables you to resize the window, whereas CV_WINDOW_AUTOSIZE adjusts automatically the window size to fit the displayed image (see imshow() ), and you cannot change the window size manually.
• CV_WINDOW_FREERATIO or CV_WINDOW_KEEPRATIO: CV_WINDOW_FREERATIO adjusts the image with no respect to its ratio, whereas CV_WINDOW_KEEPRATIO keeps the image ratio.
• CV_GUI_NORMAL or CV_GUI_EXPANDED: CV_GUI_NORMAL is the old way to draw the window without statusbar and toolbar, whereas CV_GUI_EXPANDED is a new enhanced GUI.

By default, flags == CV_WINDOW_AUTOSIZE | CV_WINDOW_KEEPRATIO | CV_GUI_EXPANDED