main screen with key areas labeled
sample of active window enhancement: the background is dimmed and blurred
Screenshot Captor has tons of options for capturing your full screen, specific regions or selected windows; it has excellent callout functions, like standard arrows and highlighting tools along with the excellent blur effect you see in the screenshot above; and it can automatically open screenshots in your favorite image editor or email screenshots as soon as you take them. In all, Screenshot Captor may be the most full-featured screenshot app and it does have a slightly steeper learning curve, so if there's a downside, that may be it.
Download: Screenshot Captor
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