Get width and height of the connected monitor

In my program, I am drawing some objects, assets and doing some operations of the screen. When I draw some objects at the center, I take the center of my window to be: ofGetWidth()/2, ofGetHeight()/2,0

My screen has W x H of 1366 x 768 and the monitor where I have to project the application has a W x H = 1920 x 1080.
Here’s a single scenario:
I have an image that should be appearing over the whole window in the background. When I don’t run the application in full screen ( and it’s in _OF_WINDOW _mode), I get the image width and height correct with _ofGetWidth() _and ofGetHeight()

However, as I soon as resize the application to full screen or run the application OF_FULLSCREEN, my background image does not cover the whole application. The image somehow still has the same smaller width and height which is retrieved by ofGetWidth and ofGetHeight don’t actually give me height of the full screen window itself.

How should I rectify this so that I get the correct height and width of the window for the image to appear in full screen and also wherever I am using the width and height at other places?

I think the getWidth() and getHeight() return the values as setup in main; while
ofGetWindowHeight()
ofGetWindowMode()
ofGetWindowPositionX()
ofGetWindowPositionY()
ofGetWindowRect()
ofGetWindowSize()
ofGetWindowWidth()

return values of the current window. Try using those.