The Interactive Contour Plot command
interactively marks intensity contours on an image. It operates
from Interactive Contour Plot Toolbar. The contour follows a
path of constant intensity, perpendicular to the local gradient.
This is a point & click tool in which you click the mouse on
the point having the intensity at which you want to create a
contour. The related
Contour Plot command plot contours non interactively
using one or more specified levels.
Open the Interactive Contour Plot Toolbar
using the Plot > Interactive Contour command from the
top-level Image menu or the button on the
Image Plot Toolbar.
The contour may be generated inside the
Image Cursor or you can contour the entire image.
There are a number of
Properties that control generation and display
of the contours. Be advised that contouring the entire image by
clicking on noise can take a very long time to compute.
Tip
You can terminate the contour computation at any
time by hitting the [Esc] key. This
is especially handy if you start a contour computation after
accidentally clicking on a level far into the noise.
Toolbar Commands
Interactive contour plotting uses the
Interactive Contour Plot Toolbar shown below. This is opened
from the top-level
Image Plot Toolbar. or the Plots > Contour Toolbar.
To interactively mark contours, enable marking mode
by pressing the top toolbar button, then click on the image to
compute the contour.
In regions of high noise, you can reduce noise
tracking by increasing the contour smoothing. For more information
about contour plotting in noisy areas of an image, see
Contour Plot Smoothing.
Note
It is usually advisable to constrain the contour to
a rectangle inside the image cursor. Contours require drawing many
short lines, and a complex contour containing a large number of
line segments may cause the computer to lag every time the image
window needs to be redrawn.
With many complex contours visible, display
updating can be sluggish on slower computes. On a given computer,
you can speed up re-drawing time try the following solutions:
increase smoothing, confine the contours to a rectangle of smaller
size, or delete the contour using the (delete all) button on the
toolbar.