Contour computes isocurves (contours) within a slice of a dataset.
When linked into an application that draws an image (e.g. Image),
the contours will be drawn as overlays. The contours can be accessed from
the overlay menu in such an application once transmitted; they can be hidden
or re-viewed that way. Contours are drawn within meta data space, so if
datasets do not match at all in meta data, putting contours from one onto
another will not be effective. If contours from several different datasets
are to be overlaid onto a single image, one may use multiple contour applications,
linking each into the image application. Which contours are to be drawn
can then be controlled from the overlay menu. The contours will be identified
by the name and number at the top of the contour window (e.g., "Contour_1").
Multiple contour levels can be made within the same dataset. See use
of the Add and Delete buttons below. Contour will allow a maximum of 8
contour levels at the same time.
The current contour level is chosen by moving the slider below the histogram.
Note the vertical line in the histogram image will track the slider position.
The bottom three sliders set the color of the current contour. The sliders
are red, green, and blue components of the color; the line in the histogram
will be drawn in the selected color.
To create a second (and subsequent) contour level, adjust the slider to
the proper location of the first level, then hit the Add button. A new
contour level will be activated. It will appear on the far left of the
histogram; the current contour is noted by the gray triangle at the top
of the window. The current (new) contour level can now be adjusted. If
it is no longer desired, the Delete button will remove it and the previous
contour will become current.
The Save button will draw the current contour(s) into a file in overlay
format. It might be useful to store these in the overlay directory.
Contour will let you adjust contour levels until you hit Send. It will
then compute the contours you have selected and transmit them to all linked
The histogram will display either a histogram of just the current slice
or of the whole dataset. Two menu options allow toggling between those
Contour will label contour levels with the contour value if desired.
The "Include Labels" menu item will turn this feature on. "No Labels" will
turn it off.
If several contour levels are to be chosen, it might be convenient to
have them spaced evenly. The "Space Evenly" menu option changes the meaning
of the slider and adds a thumbwheel. The thumbwheel determines how many
contours (2-8) are to be drawn. The slider has two beads, their positions
indicate the lowest and highest contour level to use. The remaining contours
will be evenly spaced between those two levels. "Select Singly" returns
Contour to the normal mode of operation.
Applications to Connect to This Application
Any slider is useful to select a slice. One can set the color table for
the histogram drawn in Contour with a color tool, but it won't propagate
from there. A bounding box will limit the samples in the histogram, but
will not limit generated contours.
Applications to Connect This Application to
Any Data Object may be connected via the
"drag 'n drop" button to this application. Image,
and Window Tool can draw contours.
Tricks and Gotchas
Contour will compute and send a contour upon linking or upon the hitting
of the Send button. If a contour is complicated enough to take some time
to compute, one might want to select the contour level before linking in
order to avoid having the default level be used.
If a dataset's meta data values are very very small (on the other of
10E-40) or very very large (on the order of (10E40)), contours may be incorrect
due to numerical over- or underflow.
/ Oct 5, 2001