Provided by: grass-doc_7.4.0-1_all 
NAME
v.colors - Creates/modifies the color table associated with a vector map.
KEYWORDS
vector, color table
SYNOPSIS
v.colors
v.colors --help
v.colors [-rwlngac] map=name [layer=string] use=string [column=name] [range=min,max]
[color=style] [raster=name] [raster_3d=name] [rules=name] [rgb_column=name]
[--help] [--verbose] [--quiet] [--ui]
Flags:
-r
Remove existing color table
-w
Only write new color table if it does not already exist
-l
List available rules then exit
-n
Invert colors
-g
Logarithmic scaling
-a
Logarithmic-absolute scaling
-c
Convert color rules from RGB values to color table
Option ’rgb_column’ with valid RGB values required
--help
Print usage summary
--verbose
Verbose module output
--quiet
Quiet module output
--ui
Force launching GUI dialog
Parameters:
map=name [required]
Name of vector map
Or data source for direct OGR access
layer=string
Layer number or name
Vector features can have category values in different layers. This number determines
which layer to use. When used with direct OGR access this is the layer name.
Default: 1
use=string [required]
Source values
Options: attr, cat, z
Default: cat
attr: read values from attribute table (requires <column> option)
cat: use category values
z: use z coordinate (3D points or centroids only)
column=name
Name of column containing numeric data
Required for use=attr
range=min,max
Manually set range (refers to ’column’ option)
Ignored when ’rules’ given
color=style
Name of color table
Options: aspect, aspectcolr, bcyr, bgyr, blues, byg, byr, celsius, corine, curvature,
differences, elevation, etopo2, evi, fahrenheit, gdd, grass, greens, grey, grey.eq,
grey.log, grey1.0, grey255, gyr, haxby, kelvin, ndvi, ndwi, oranges, population,
population_dens, precipitation, precipitation_daily, precipitation_monthly, rainbow,
ramp, random, reds, roygbiv, rstcurv, ryb, ryg, sepia, slope, soilmoisture, srtm,
srtm_plus, terrain, viridis, water, wave
aspect: aspect oriented grey colors
aspectcolr: aspect oriented rainbow colors
bcyr: blue through cyan through yellow to red
bgyr: blue through green through yellow to red
blues: white to blue
byg: blue through yellow to green
byr: blue through yellow to red
celsius: blue to red for degree Celsius temperature
corine: EU Corine land cover colors
curvature: for terrain curvatures (from v.surf.rst and r.slope.aspect)
differences: differences oriented colors
elevation: maps relative ranges of raster values to elevation color ramp
etopo2: colors for ETOPO2 worldwide bathymetry/topography
evi: enhanced vegetative index colors
fahrenheit: blue to red for Fahrenheit temperature
gdd: accumulated growing degree days
grass: GRASS GIS green (perceptually uniform)
greens: white to green
grey: grey scale
grey.eq: histogram-equalized grey scale
grey.log: histogram logarithmic transformed grey scale
grey1.0: grey scale for raster values between 0.0-1.0
grey255: grey scale for raster values between 0-255
gyr: green through yellow to red
haxby: relative colors for bathymetry or topography
kelvin: blue to red for temperature in Kelvin scale
ndvi: Normalized Difference Vegetation Index colors
ndwi: Normalized Difference Water Index colors
oranges: white to orange
population: color table covering human population classification breaks
population_dens: color table covering human population density classification breaks
precipitation: precipitation color table (0..2000mm)
precipitation_daily: precipitation color table (0..1000mm)
precipitation_monthly: precipitation color table (0..1000mm)
rainbow: rainbow color table
ramp: color ramp
random: random color table
reds: white to red
roygbiv: no description
rstcurv: terrain curvature (from r.resamp.rst)
ryb: red through yellow to blue
ryg: red through yellow to green
sepia: yellowish-brown through to white
slope: r.slope.aspect-type slope colors for raster values 0-90
soilmoisture: soilmoisture color table (0.0-1.0)
srtm: color palette for Shuttle Radar Topography Mission elevation
srtm_plus: color palette for Shuttle Radar Topography Mission elevation (with
seafloor colors)
terrain: global elevation color table covering -11000 to +8850m
viridis: perceptually uniform sequential color table viridis
water: water depth
wave: color wave
raster=name
Raster map from which to copy color table
raster_3d=name
3D raster map from which to copy color table
rules=name
Path to rules file
rgb_column=name
Name of color column to populate RGB values
If not given writes color table
DESCRIPTION
v.colors allows creating or modifying color table associated with a vector map similarly
to r.colors for raster maps.
Color rules are built from features category values (use=cat) or numeric data column
(use=attr) defined by column option. For 3D vector maps is allowed to define color rules
based on points or centroids z-coordinate (use=z). 3D vector lines are not supported.
The raster option allows user to specify a raster map from which to copy the color table,
similarly raster_3d option for 3D raster map.
The rules color table type will cause v.colors to read color table specifications from
given file and will build the color table accordingly. See r.colors manual page for
details.
If the user specifies the -w flag, the current color table file for the input map will not
be overwritten. This means that the color table is created only if the vector map does not
already have a color table. If this option is not specified, the color table will be
created if one does not exist, or modified if it does.
Alternatively the color rules can be stored in a string column (rgb_column) by saving the
RRR:GGG:BBB values suitable for use with d.vect.
NOTES
For vector maps with a large number of features it’s more convenient to store color rules
in an attribute column (given by rgb_column) rather then in a color table file. Reading
color tables with more then 1000 items is slow.
EXAMPLES
Define color table based on categories
Define color table wave based on categories from layer 1
v.colors map=soils_general layer=1 color=wave
Define color table based on attribute values
Define color table ryg based on values from attribute column AREA. Attribute table is
linked to layer 1.
v.to.db map=soils_general layer=1 option=area column=AREA
v.colors map=soils_general layer=1 color=wave use=attr column=AREA
Define color table stored as RGB values in attribute table
Write color values to the attribute table (column GRASSRGB) instead of creating color
table.
v.colors map=soils_general layer=1 color=wave use=attr column=AREA rgb_column=GRASSRGB
# See some GRASSRGB values:
v.db.select map=soils_general where="cat < 4"
cat|OBJECTID|AREA|PERIMETER|GSLNC250_|GSLNC250_I|GSL_NAME|GRASSRGB
1|1|0|164616.125|2|1|NC113|212:42:127
2|2|0|30785.529297|3|2|NC096|212:42:127
3|3|0|87572.882812|4|3|NC097|212:42:127
Convert RGB attribute values into color table
Convert existing RGB values to color table rules.
v.colors -c map=soils_general rgb_column=GRASSRGB
Note that in this case the vector map has a proper color table assigned (check by
v.colors.out) together with GRASSRGB attribute column. Also note that color table is
preferred over RGB values stored in attribute table.
Remove existing color table
Existing color table can be removed by -r flag.
v.colors -r map=soils_general
Before removing color table you can store color rules to the file by v.colors.out and
later to assign by rules option.
v.colors.out map=soils_general rules=soils.colr
v.colors map=soils_general rules=soils.colr
To drop RGB column use v.db.dropcolumn.
v.db.dropcolumn map=soils_general column=GRASSRGB
SEE ALSO
d.vect, r.colors, r.colors.out, r3.colors, r3.colors.out, v.colors.out
See also wiki page Color tables (from GRASS User Wiki)
ColorBrewer is an online tool designed to help people select good color schemes for maps
and other graphics.
AUTHORS
Martin Landa, OSGeoREL, Czech Technical University in Prague, Czech Republic
Last changed: $Date: 2015-02-13 16:14:07 +0100 (Fri, 13 Feb 2015) $
SOURCE CODE
Available at: v.colors source code (history)
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