Use this tool to calibrate your measurements.
- Click the Unit tool .
- Identify a line in the image of which the length is known, and then click one end of that line.
- Click the other end of the line.
- Enter the real length and select the unit in the dialog box that appears.
- Click the option "Use this as the default calibration" if you want to use this calibration for next images.
- Click OK.
The length (in pixels) is displayed in the Measurements list window.
When the option Show result after finalizing measurement is selected, then the length is displayed in a small window next to the object.
After you have defined the unit, all previous measurements are recalculated.
A default calibration can also be defined in the options box.