Constant intensity-contours provide an
alternate way of displaying the data, replacing the false color
display controlled by the
color scale and
color scheme. Constant intensity contours
are drawn at selected intensity levels. The resulting image can be
zoomed or written to a file
in the normal way.
Clicking on the Contour button switches from Linear or Logarithmic mode to
contour mode. The default is a set of logarithmically spaced contour lines.
The number of contours, intensity value for each contour, and color of each
contour line can be altered in a new window that is opened using the Levels button.
The contours will be immediately redrawn if you click the Apply button, assuming that
you have already clicked the Contour button--otherwise, the changes will take
effect the next time you go into contour mode.
If you decide to play with the contour levels and/or colors, keep the following in mind:
- The program assumes that the intensity levels are in increasing order.
Arranging them any other way may lead to unpredictable results.
- The time to draw the image is approximately proportional to the number of
contour lines chosen. You will see a real decrease in performance if you select
too many contour lines.
- Too many contour lines can also make an image too busy.
- Adjacent contour lines should have very different colors, otherwise you will
not be able to figure out where the changes happen.
- You cannot change the parameters of a contour line whose index is greater than
the maximum number of lines to be drawn.
- The ultimate information of the data is limited by the pixelation. Things may
look a little odd at extreme magnification.
- Low-statistics data will result in very noisy, fractal-looking contour lines, because
the contour lines faithfully follow the contours of the data including statistical
fluctuations. If you are looking at broad features (which is typically the case if
you are using contours at all) consider using the
Condense option to bin together pixels, resulting in better
statistics but poorer resolution.
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