added ColorProperty to set background color

[jwendelmuth]

No description provided.

[lucasw]

Check out rviz ColorProperty.

[NikolasE]

I think this would provide a bit too much choice. A purple background probably does not have many use cases.

[lucasw]

What if the Global Options Background Color were used?
Is there a use case where the rviz camera would need a different background color than the standard rviz render window?

[NikolasE]

I personally like to have a black RVIZ background to work with, but it does not look good if the image is integrated into a document (thesis or bugreport).

[lucasw]

It seems like the default behavior should be that the rviz camera background is the same as the main rviz window. If there is a need to have two different background colors at the same time, then there should be a full color property (and a checkbox to enable it, or can switching between them be handled otherwise?).

I like a color background to distinguish it from foreground objects that are frequently monochrome.

For future reference another useful capability would be to optionally have a transparent background in an rgba Image.

[lucasw]

Squashed and merged with c20d2bb

[lucasw]

The background color doesn't match desired as revealed by #14 (channels are swapped), it will be corrected separate from this.