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Truthful colour tables
| Truthful colour tables [message #40749] |
Fri, 27 August 2004 09:59 |
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Justin[3]
Messages: 8
Registered: November 2003
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Junior Member |
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Hello all,
After plotting lots of spectra with the "rainbow" colour table it became
clear to me that such a table hides much detail and over-emphasises some
features.
Clearly this is not a new idea and hunting around I came across the
excellent article "How NOT to Lie with Visualization":
http://www.research.ibm.com/dx/proceedings/pravda/truevis.ht m.
There was also a brief discussion in this group back in Feb of this year
After reading the article I tried to create such an "isomorphic" colour
table (top-right in figure 1) myself in IDL. They describe the table as
follows:
"In this colormap [colour table], luminance and saturation both increase
monotonically with data value. That is, brightness increases
monotonically and hue, which begins as a pure vivid blue, becomes more
and more pastel."
The don't say the (monotonic) increase is linear so I'm guessing it's
not. Also the values don't seem to start from zero either. And to add to
the confusion they're talking about luminance rather than lightness used
in the HLS colour space of IDL (though I think "brightness" is the same
and "value" from the HSV model). Also they show an interesting
blue/yellow map in Figure 2 (clearly with a non-linear and non-monotonic
hue).I did try to download the PRAVDAcolor software mentioned but
couldn't find all of it.
So (finally) my question is, does anyone know what these colour tables
are and how the components vary? I don't mind creating the tables myself
in IDL if I had a plot or description of the colour components. These
guys have obviously put a lot of effort in the work so it would be a
shame not to use it!
Thanks,
Justin
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