ScreenRuler

ScreenRuler is a visual software tool to assist with reading on the Mac. The ScreenRuler software provides a strip or ruler across the screen, which can have the contrast changed and have the background greyed, colored or dimmed out.

ScreenRuler allows part of the screen to be highlighted or underlined depending on the users preference. It also has support for dual monitor and full screen overlay functions.
MODES
There are three possible ScreenRuler modes that are configurable in the ScreenRuler Settings screen:
★ Ruler - This is the default setting. It provides a reading ruler across the current screen and will shade out above and below the ruler for easier viewing.
★ Underline - Provides a line across the current screen.
★ Overlay - Provides a full screen color overlay.
SETTINGS
Once ScreenRuler has been launched, it will stay as an open application and will work with all software applications, following the mouse pointer. It is possible to change how ScreenRuler looks by changing the settings in the ScreenRuler Settings screen.
The following can be edited in the Preferences Window:
Ruler
★ Color - Click on the colored box to change the color of the ruler.
★ Shading Level - Move the slider to change the transparency level of the ruler.
★ Size - Move the slider to change the height of the ruler.
Outside Ruler (background)
★ Color - Click on the colored box to change the color of the background/outside of the ruler.
★ Shading Level - Move the slider to change the transparency level of the area outside of the ruler.
★ Shading - Check the 'shade above ruler' and 'shade below ruler' boxes to show the corresponding shading above/below the ruler.