Default wallpaper in 16:4 landscape in portrait orientation?

I'm trying to set an image on my phone, but i want the full image in 16:4 format, while in portrait orientation. as in there is black bars on top and bottom of the image. any help would be greatly appreciated and if you want me to further explain, I'll gladly do so.

Sent from my Nexus 5 using XDA Premium 4 mobile app
Google Nexus 5 (hammerhead) Black, 32GB
ROM: Paranoid Saberdroid
Kernel: Code Blue

Nexus 7 (2013) (flo) Black, 32GB
ROM: Paranoid Saberdroid
Kernel: Franco Kernel

MultiROM