GRASS GIS manual: v.colors

Note: A new GRASS GIS stable version has been released: GRASS GIS 7.4, available here.
Updated manual page: here

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, 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, rstcurv, ryb, ryg, sepia, slope, srtm, srtm_plus, terrain, 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; 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; 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; 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; 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
NOTES
EXAMPLES
SEE ALSO
AUTHORS

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

AUTHORS

Martin Landa, OSGeoREL, Czech Technical University in Prague, Czech Republic

Last changed: $Date: 2015-02-13 07:16:22 -0800 (Fri, 13 Feb 2015) $

SOURCE CODE

Available at: v.colors source code (history)