Tap and hold an app to make all your apps shake (how you delete apps), move all 4 of your apps on the bottom bar (the one that is at the bottom of every app page) to a page with other apps on it so it is blank. Slide over to a completely blank page (you can do this while app delete is activated), then take your screen shot. You will only have a small grey bar across the bottom of your image. If the image you want is on your lock screen instead of your home screen this will not help you.