Ran into a problem sharing some pages from the TDF wiki.
Apparently there is at least once case of a page using a background image,
in the head of page, and then floating another .png image over it with Text
and transparent background.
The problem is that when that is shared what gets picked up is the top
.png, which in this case is using white text since the background is green,
but in the external system that .png with transparent background is now
placed on a white background.