background screenshot subwindow

Is it possible to make a subwindow screenshot (Ctrl+F3) without the grey background.

i think if you change the background color in the ‘themes’ panel. go to the top of the interface, and place your mouse arrow over the border between the 3D window and the top of the interface, and then Lclick and drag down the upper button panels. Click on ‘themes’ then ‘add new’, and then you can select from a couple of lists what you want to change. select background, and adjust the RGB sliders to the color you want.

I can change the background color but is it possible to render or make a subwindow screenshot without a background. may be transparant.