Sprightly Software today announced Screen Ruler 3 for Mac OS X, an update to the utility for working with on-screen graphics. It requires Mac OS X 10.7 or higher, costs US$14.99 and is available worldwide exclusively through the Mac App Store in the Developer Tools category.

Screen Ruler runs from the Menu Bar, and includes keyboard shortcuts. You can take accurate measurements anywhere on-screen, even across multiple displays. New in version 3.0 is support for Mountain Lion, a new compact interface, a new zoomed-in cursor view, persistent rulers, and more.

Screen Ruler’s Box Measurement Tool provides a way to get the exact pixel width and height of an area anywhere on your display. The Line Measurement Tool determines the length between any two pixels. The Color Picker provides a way to obtain a web-ready hex color, or Core Graphics compatible RGB fraction from anywhere on your display. The Grab Image Tool allows one to take a screenshot of anything on-screen.