ZFP - Change the style of image overlay(annotation) to same as CWEB. (CWEB parity)

The style of image overlay(annotation) is white text on black ground.

The black ground hides image if overlapped.

Expect behavior:

The style of image overlay(annotation)is white text on black text same as CWEB.

In addition, measurement tools and their text don't hide image if overlapped. It is also the expect behavior.