What size should the background image be so it is not scaled?

What dimensions should an image file have so that it will not be scaled when set as a wallpaper for the lockscreen or homescreen? This question is NOT the same as https://android.stackexchange.com/questions/2026/what-is-the-default-resolution-of-a-wallpaper-that-fits-the-homescreen-exactly-i . I only have a single home screen. I already tried the dimensions of the screen. That does not work since the image is zoomed in slightly, so that it can be zoomed out when pulling down the notifications menu. On my phone, the Nokia 5.4, the screen resolution is 720x1560. My best guess at the best wallpaper resolution is 792x1778, however that size is still not perfect.