i'm not sure what u captured. if u captured a 'region', u should not have to edit it to get rid of the image of the player.
this is what i do to capture a region:
1> Input -> Region
2> Output -> File
3> ctrl+shift+p changes the mouse pointer to a crosshair
4> click and hold on the topleft corner of the region that i wanna shoot
5> drag a square to select the region
6> release mouse button to finish capture
7> save it to file
that's how i just captured this 'Post Quick Reply' window