
read_colormap_file
Reads an NCL system colormap file or a user-defined colormap.
Available in version 6.1.0 and later.
Prototype
function read_colormap_file ( filename : string )
Arguments
filenameThe name of a colormap from NCL's system colormaps, or the name of a file containing a user-defined color map.
Return value
A float array of size n x 4 is returned, where n is the number of colors in the colormap. Colors are 4-tuples of red, green, blue, opacity values, in the range [0., 1.].
Description
[Note: in NCL versions 6.1.2 or earlier, you must load "$NCARG_ROOT/lib/ncarg/nclscripts/csm/gsn_code.ncl" to use this function. In later versions, you don't need to load anything.]
This is a convenience function for loading NCL's system colormaps or user-specified colormaps. While general-purpose in nature, its primary use-case is loading colormaps that are then assigned to resources such as cnFillPalette, cnFillColors, vcLevelPalette, vcLevelColors, stLevelColors, stLevelPalette, or mpFillColors.
Note that the function always returns 4-component colors, consisting of red/green/blue/opacity values. If the source color tables do not contain opacity values, a default of 1.0 (opaque) is returned.
The function follows all the naming and searching conventions for locating files as described here.
See Also
draw_color_palette, namedcolor2rgb, gsn_define_colormap span_color_indexes, span_color_rgba, get_color_index, get_color_rgba, span_named_colors
Examples
For several examples of manipulating color using the new color display introduced in NCL V6.1.0, see the "New color capabilities" examples page.
Example 1
This example shows how to read an existing color map, and then subscript part of it for a filled contour plot:
cmap = read_colormap_file("BlAqGrYeOrReVi200") ... res@cnFillColors = cmap(3:,:) ; Skips the first two colorsExample 2
This example shows how to read an existing color map, and make part of it transparent for a filled contour plot:
cmap = read_colormap_file("OceanLakeLandSnow") ... cmap(0:1,3) = 0.0 ; Make first two blue colors fully transparent res@cnFillColors = cmap