How to save bitmap to rgb pixelformat in firemonkey?

Dear:

 When I make MakeScreenshot and save to file. The file format is default to 32bit(BGRA). how to save to other format?

 like  RGB, BGR_565 etc.

It is easy to do in VCL. only set pixelformat.  but in firemonkey, the property is readonly. 

SpeedButton1.MakeScreenshot.savetofile('d:\sample.bmp');