GRASS GIS manual: v.colors

## 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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