In the Iso-contour Mode the cursor changes to
As soon as the left mouse button is clicked into an image, the pseudo-snake algorithm tries finding the largest closed iso-contour at the clicked image value and represents it as a closed polygon.
Note: Each time the button is clicked, the contour is replaced by a new iso-contour. This behavior is in contrast to the other drawing modes which require to first clear a contour, or opening it.
The automatic mode of iso-contouring guesses whether the user is aiming at a hot or cold contour. If the behavior is not satisfactory, the user can select the appropriate mode from the option list next to the iso-contour button as illustrated below.