matte shadow on white background

[lukx]

Ok might sound strange but client wants a render with matte shadow alpha but on white background. I would like to avoid adding white background in photoshop and basically want to render object on white background with matte shadow alpha. Right now when using Corona shadow catcher I'm getting black background with shadow alpha. Anyway to get white background and shadow alpha?
In my attached examples first one is render straight from Corona. Second one is collapsed white background and added corona alpha shadow and this is what I want straight form render engine.

[Jpjapers]

I may have misunderstood but could you simply save as jpeg instead of png to lose the transparency of the alpha?

[sprayer]

why don't you make batch action for photoshop?

[maru]

I can't see a way to do this in one go, because the shadowcatcher in "for compositing" mode will always render as black.