Pixel Winch (beta) is a screen measurement app with a unique approach. Rather than overlaying complicated controls on top of your existing workflow, it combines aspects of a traditional image editor with the quick access of a modal interface (similar to OS X's Launchpad or Dashboard).
Select a region on the screen to load it inside of Pixel Winch.
Need to look up previous measurements? No problem - use the history list to revisit past images. Worried about images clogging up your hard drive? Pixel Winch can be configured to automatically delete them.
Shapes
The Line Tool and Rectangle Tool draw shapes on top of the captured image. All shapes display their measurements and can be moved or resized.
Grapples
The Grapple Tool draws a horizontal or vertical line outward from the cursor until it detects an edge. Use the lowest power level to measure a solid color or increase it for a gradient.
Guides
Click and drag from either ruler to place horizontal or vertical guides. In addition to their standard use as visual alignment aids, guides prevent grapples from traversing through them. Use them in combination with grapples for complex measurements.
And More!
Pixel Winch includes standard tools found in most image editors. The Zoom Tool magnifies the canvas up to 6400% while the Hand Tool enables fast panning. Use the Marquee Tool to copy parts of the image and the Move Tool to select and move existing shapes.
Features: Industry standard tools and keyboard shortcuts Support for Retina displays and multiple monitors Ability to multiply all measurements by 25%, 50%, 100%, or 200% Stores all previous screenshots and measurements Automatically deletes stored screenshots after a customized time interval Customizable colors for guides, lines, and rectangles Global keyboard shortcuts for Capture Selection and Show Screenshots