There are three types of built in color maps
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Standard maps
Includes rainbow spectrum and heat maps and combination of plain red-green-blue maps
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Normalized center
These maps have a white:ish center. This is mostly useful to visualize the spread from a center value
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Continues
The maps have one base color where the hue changes
In the color maps in the following section the black bars under some colors in the color map shows the discrete colors (the plateaus) that the color map is made up of. All colors in between two "barred" colors are linear interpolations.
The script that was used to generate these color maps can be found under the example
directory as "colormaps.php".
To show heat gradient map 0 is the standard color map. To highlight the min and max values (to get a high contrast) map 3 is a good choice. Map two is a standard "rainbow" spectrum from red all up to violet.
These maps have a neutral (white) center and feathers out to the min/max value at each end.
