rvbszAuto

The size is adjusted proportionally to the opposite dimension. If the both dimensions are rvbszAuto, the original image size is used.

rvbszContain

Scales the background image so that the entire image fits within the background rectangle while preserving its aspect ratio

rvbszCover

Scales the background image so that the entire background rectangle is covered while preserving the aspect ratio

rvbszValue

Scales the background image to the specified size