Custom background colour in pdf files?

[jackm8]

I'm wondering if there's a way to change the background colour for pdf files in Koreader from pure white, to say, pure black?

It's really nothing major. I usually batch canvas size individual images so that they get black borders. I'm just wondering if there's a way to adjust this in the reader itself.

Sample images. First one is how it looks in the reader when no cropping is selected, the second image is how I'd like it to look.