As part of the installation four standard JPEG images are supplied.

Earth.jpg - standard image of the earth.
whiteglow.jpg - continents surrounded by a white glow.
blueglow.jpg - continents surrounded by a blue glow.
mars.jpg - image of the Martian surface.

Any other JPEG true color images desired as a background can be placed in the backgrounds sub-directory. The only requirement is that they be 3xMxN true color images. Upon startup mapViz will search the backgrounds sub-directory for JPEG files. It will then create one button per file, with the button name matching the file name.

A background image is always the last object in the drawing order. e.g. nothing else (lines, coasts, etc) is ever behind it. If the user wishes to treate an image as an object layer then it should be added in with the add method.

NOTE:
Whenever the map is resized or zoomed in on the background image files are re-read and re-scaled. This is done so that no unnecessary resolution is lost. However, this does cause a performance hit, especially when the background images are large.