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 [column=name] [range=min,max] [color=style] [raster=name] [volume=name] [rules=name] [rgb_column=name] [--verbose] [--quiet]

Flags:

-r: Remove existing color table
-w: Only write new color table if one doesn't 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
--verbose: Verbose module output
--quiet: Quiet module output

Parameters:

map=name [required]: Name of vector map; Or data source for direct OGR access
layer=string [required]: Layer number or name; A single vector map can be connected to multiple database tables. This number determines which table to use. When used with direct OGR access this is the layer name.; Default: 1
column=name: Name of column containing numeric data; If not given categories are used
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, byg, byr, celsius, corine, curvature, differences, elevation, etopo2, evi, gdd, grey, grey.eq, grey.log, grey1.0, grey255, gyr, haxby, ndvi, population, population_dens, precipitation, precipitation_monthly, rainbow, ramp, random, rstcurv, ryb, ryg, sepia, slope, srtm, 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; 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; gdd: accumulated growing degree days; 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; ndvi: Normalized Difference Vegetation Index colors; 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_monthly: precipitation color table (0..1000mm); rainbow: rainbow color table; ramp: color ramp; random: random color table; 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; terrain: global elevation color table covering -11000 to +8850m; wave: color wave
raster=name: Raster map from which to copy color table
volume=name: 3D raster map from which to copy color table
rules=name: Path to rules file; "-" to read rules from stdin
rgb_column=name: Name of color column to populate RGB values; If not given writes color table

DESCRIPTION

v.colors allows the user to create and/or modify the color table for a vector map. The vector map (specified on the command line by map) must exist in the user's current mapset search path.

As input a vector map with a numeric data column is required which is used to apply the color rules. The color values are stored in a string column (default name "GRASSRGB", varchar(11)) by saving the RRR:GGG:BBB values suitable for use with 'd.vect -a'. If this RGB column is not found in the attribute table, it is automatically created.

The rast option allows user to specify a raster map name from which to copy the color map.

The volume option allows user to specify a volume (3D raster) map name from which to copy the color map.

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 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.

In general, tables which associate colors with percentages (aspect, bcyr, byg, byr, elevation, grey, gyr, rainbow, ramp, ryb, ryg and wave) can be applied to any data, while those which use absolute values (aspectcolr, curvature, etopo2, evi, ndvi, population, slope, srtm, and terrain) only make sense for data with certain ranges. One can get a rough idea of the applicability of a colour table by reading the corresponding rules file ($GISBASE/etc/colors/<name>). For example the ryg rule is defined as:

0% red
50% yellow
100% green

The rules color table type will cause r.colors to read color table specifications from standard input and will build the color table accordingly.

For details see r.colors manual page.

EXAMPLES

Define color table wave based on categories from layer 1

v.colors map=soils_general layer=1 color=wave

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 column=AREA

Write color values to the attribute table (column GRASSRGB) instead of creating color table.

v.colors map=soils_general layer=1 color=wave column=AREA rgb_column=GRASSRGB

# See some GRASSRGB values:
v.db.select map=soils_general | head -n 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 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 prefered over RGB values stored in attribute 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 > 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, Czech Technical University in Prague, Czech Republic

Last changed: $Date: 2011-11-14 02:46:47 -0800 (Mon, 14 Nov 2011) $

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