NOTE: This is the default for the left mouse button.
You can draw a line to measure the distance in millimeters between items in images. The graphic is added automatically as a bookmark. Open the Bookmark list to see its details.
1. From the Viewer, select an image.
2. In the Graphics tab of the toolbar, click Line Measurement 
in the Measurements ribbon.
3. Click on the image where you want the line to start.
4. Click where you want the line to end.
Right-click on the line
NOTE: An image must have a calibration provided by the original scanner source or by manual calibration. See Calibrating Images.
Right-click on a drawn line and click Show Profile to display a curve showing the intensity values of the pixels along the line.
