Use the Background - Export Backdrops tool to export the bitmaps that are used as backdrops on selected backgrounds.
Note: you can collapse this dialog by clicking on the collapse graphic () at the top of the screen and then expand it again by clicking the expand graphic ().
Click on the screen elements for details.
Backgrounds (with backdrops) list
Export (backdrops) button
Prompt Before Overwriting
Select All button
Select Directory field and button
Select None button
Use Name When Possible