v.colors(1)

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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