NAME
r.colors.cubehelix - Create or apply a cubehelix color table to a GRASS raster map
KEYWORDS
raster,
color table,
cubehelix,
seaborn
SYNOPSIS
r.colors.cubehelix
r.colors.cubehelix --help
r.colors.cubehelix [-dngae] [map=name[,name,...]] [output=name] [start=float] [nrotations=float] [gamma=float] [hue=float] [light=float] [dark=float] [ncolors=integer] [--overwrite] [--help] [--verbose] [--quiet] [--ui]
Flags:
- -d
- Generate discrete color table
- Generate discrete (interval) color table instead of a continuous one
- -n
- Reverse the order of colors (invert colors)
- If set, the color table will go from dark to light
- -g
- Logarithmic scaling
- -a
- Logarithmic-absolute scaling
- -e
- Histogram equalization
- --overwrite
- Allow output files to overwrite existing files
- --help
- Print usage summary
- --verbose
- Verbose module output
- --quiet
- Quiet module output
- --ui
- Force launching GUI dialog
Parameters:
- map=name[,name,...]
- Raster map(s) to apply color table to
- output=name
- Name for the new color table rules file
- start=float
- The hue at the start of the helix
- Options: 0-3
- Default: 0
- nrotations=float
- Rotations around the hue wheel
- Rotations around the hue wheel over the range of the color table
- Options: 0-3
- Default: 0.4
- gamma=float
- Gamma factor to emphasize darker (<1) or lighter (>1) colors
- Options: 0-
- Default: 1.0
- hue=float
- Saturation of the colors
- Options: 0-1
- Default: 0.8
- light=float
- Intensity of the lightest color in the color table
- Options: 0-1
- Default: 0.85
- dark=float
- Intensity of the darkest color in the color table
- Options: 0-1
- Default: 0.15
- ncolors=integer
- Number of colors in the color table
- Number of color intervals in a discrete color table with -d
- Options: 2-
- Default: 6
The
r.colors.cubehelix module generates
a cubehelix color table and assigns it to a given raster map
if requested.
The color table is generated using
seaborn Python
package. Several parameters are available to control the
cubehelix.
When option
map is specified
r.colors.cubehelix
assigns the color rules to the given raster map.
The color tables are always stretched based on the range of values of the map
Depending on the use case,
it may be advantageous to use the -d to discretize
the color table into intervals.
This module depends on
seaborn
which needs to be installed on your computer.
Use your Python package manager (e.g.
pip) or distribution package
manager to install it.
We do 0.6 rotation around the axis and use discrete (interval) color table
rather than the standard continuous.
If we don't specify output file, it is printed to standard output:
r.colors.cubehelix -d ncolors=5 nrotations=0.6
0.000% 218:222:192
20.000% 218:222:192
20.000% 198:166:136
40.000% 198:166:136
40.000% 173:108:112
60.000% 173:108:112
60.000% 119:61:98
80.000% 119:61:98
80.000% 48:28:59
100.000% 48:28:59
Now we set several different color tables for the elevation raster map
from the North Carolina sample dataset.
We use continuous and discrete color tables (gradients).
The color tables are stretched to fit the raster map range.
r.colors.cubehelix -d ncolors=8 nrotations=0.6 map=elevation
We can display legend:
d.legend raster=elevation labelnum=10 at=5,50,7,10
Here we set continuous color table with more colors
r.colors.cubehelix nrotations=1.4 start=4 map=elevation
First we create a text file with color rules:
r.colors.cubehelix -i rot=0.6 output=cubehelix.txt
Then we set color table for the vector to the rules stored in a file:
v.colors map=points rules=cubehelix.txt
Color table for 3D raster map can be set in the same way.
r.colors,
v.colors,
r3.colors,
r.cpt2grass,
r.colors.matplotlib
seaborn
cubehelix_palette
function documentation and an
example
Vaclav Petras, NCSU OSGeoREL
SOURCE CODE
Available at:
r.colors.cubehelix source code
(history)
Latest change: Thursday Feb 03 09:32:35 2022 in commit: f17c792f5de56c64ecfbe63ec315307872cf9d5c
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