Taking bitmapdata of an image scaled down with overlay objects on the image?

hi guys, i got this image i scaled down by .5. The user is then allowed to add objects to the image such as flowers that are sprites in the library. So basically, a jpeg that is 800 x 800 is down to 400 x 400 on the stage and the user is able to add objects to overlay the image.

i want to save the image with the flowers and objects back to its 800 x 800, how do i redraw this image using bitmapdata properly?