Try this code, it'd save the picture using Paint (.bmp file)
you can replace it with any program you like to use that may support more formats (Jpg). But maybe you'll need to change the send commands.
Hotkeys used in the script are:
Ctrl+F8 ...... capture and save
Esc............. exit
Code:
^F8::
send {Alt}{printscreen}
Run,MSPAINT.EXE
WinWait, untitled - Paint
WinActivate, untitled - Paint
Send, {CTRLDOWN}v{CTRLUP}
Send, {ALTDOWN}f{ALTUP}
Send, A
WinWait, Save As
WinActivate, Save As
Send, %A_now%.bmp{ENTER}
WinWait, %A_now%.bmp,
IfWinNotActive, %A_now%.bmp, , WinActivate, %A_now%.bmp ,
Send, {ALTDOWN}{f4}{ALTUP}
return
esc::
exitapp
return
I hope that could do what you want.