To use the linear measurement tools,
Select the linear measurement annotation button
Left-click with the mouse on the image.
While holding down the left mouse button, drag the cursor to expand the measurement ruler or region.
Release the mouse button to get the measurement value in the configured unit (millimeters, by default).
If the image object does not contain pixel size and spacing information, measurements are displayed in pixels. To convert pixels to real-world dimensions, you must calibrate the image.
To adjust the annotation graphic using the mouse,
Click on the Annotation button to enter annotation mode
Select the annotation you want to change.
To resize the graphic, left-click on one of the grab points along the edge or ends of the graphic and drag the mouse.
To move the graphic, left-click the edge of the graphic that is not a grab point and drag the mouse.