Changing Wallpaper - Why is it a pain in the a_ _ ?

[Scotty13]

What size image (px) do I need to transfer or save to my tablet, so I can crop the entire size and the entire image will display on tablet background?

Thanks,
Scotty13

 

[Scotty13]

I thought I found a program https://play.google.com/store/apps/details?id=de.j4velin.wallpaperChanger&hl=en, but i still cuts of image.