6. ref. Apple Inc. "Coordinate system" (2018)
https://developer.apple.com/library/archive/documentation/General/Conceptual/Devpedia-CocoaApp/CoordinateSystem.html
iOS macOS
47. ref. Apple Inc. "Graphics Contexts" (2012)
https://developer.apple.com/library/archive/documentation/Cocoa/Conceptual/CocoaDrawingGuide/GraphicsContexts/GraphicsContexts.html