MB-Ruler
A tool to measure distances and angles on the desktop. The distances can be measured in pixel, cm, inch, points or twips and the angle in radiant or degree. The ruler is almost transparent so you can have it on the screen, while you are working with the applications below. Additionally it has a screen loupe and a RGB value window. You can also draw points, lines, rectangles, bitmaps and text as temporary objects on the screen.
Version 3.3 adds screen cutter.
Full Specifications