Do something like
$Pic_Width = 300
$Pic_Height = 300
$Zoom_Mult = 2
GUICtrlCreatePic("C:\Test Pic.jpg",-1($Pic_Width / $Zoom_Mult),-1($Pic_Height/ $Zoom_Mult),$Pic_Width * $Zoom_Mult, $Pic_Height * $Zoom_Mult)
Then have the GUI the same size as the pic ... And use GUICtrlSetPos() for panning.
Or just double the size (2X zoom) of the pic control and the GUI holding it.
Hallman