v.colors2

Sets color rules for features in a vector map using a numeric attribute column.

Command linePython (grass.script)

v.colors2 [-sn] map=name [layer=string] column=name [rgb_column=name] [range=min,max] [color=string] [raster=name] [rules=name] [--verbose] [--quiet] [--qq] [--ui]

Example:

v.colors2 map=name column=name

grass.script.run_command("v.colors2", map, layer="1", column, rgb_column="GRASSRGB", range=None, color=None, raster=None, rules=None, flags=None, verbose=False, quiet=False, superquiet=False)

Example:

gs.run_command("v.colors2", map="name", column="name")

Parameters

Command linePython (grass.script)

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
column=name [required]
    Name of attribute column containing numeric data
rgb_column=name
    Name of color column to populate with RGB values
    Default: GRASSRGB
range=min,max
    Manually set range (min,max)
color=string
    Type of color table
    Allowed values: aspect, aspectcolr, bcyr, bgyr, byg, byr, celsius, corine, curvature, differences, elevation, etopo2, evi, gdd, grey, grey1.0, grey255, grey.eq, grey.log, gyr, ndvi, population, precipitation, rainbow, ramp, random, ryb, ryg, sepia, slope, srtm, terrain, wave
raster=name
    Name of raster map from which to copy color table
rules=name
    Name of file containing rules
-s
    Save placeholder raster map for use with d.legend
-n
    Invert colors
--help
    Print usage summary
--verbose
    Verbose module output
--quiet
    Quiet module output
--qq
    Very quiet module output
--ui
    Force launching GUI dialog

map : str, required
    Name of vector map
    Or data source for direct OGR access
    Used as: input, vector, name
layer : str, optional
    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.
    Used as: input, layer
    Default: 1
column : str, required
    Name of attribute column containing numeric data
    Used as: input, dbcolumn, name
rgb_column : str, optional
    Name of color column to populate with RGB values
    Used as: input, dbcolumn, name
    Default: GRASSRGB
range : tuple[float, float] | list[float] | str, optional
    Manually set range (min,max)
    Used as: min,max
color : str, optional
    Type of color table
    Used as: string
    Allowed values: aspect, aspectcolr, bcyr, bgyr, byg, byr, celsius, corine, curvature, differences, elevation, etopo2, evi, gdd, grey, grey1.0, grey255, grey.eq, grey.log, gyr, ndvi, population, precipitation, rainbow, ramp, random, ryb, ryg, sepia, slope, srtm, terrain, wave
raster : str, optional
    Name of raster map from which to copy color table
    Used as: input, raster, name
rules : str, optional
    Name of file containing rules
    Used as: input, file, name
flags : str, optional
    Allowed values: s, n
    s
        Save placeholder raster map for use with d.legend
    n
        Invert colors
verbose: bool, optional
    Verbose module output
    Default: False
quiet: bool, optional
    Quiet module output
    Default: False
superquiet: bool, optional
    Very quiet module output
    Default: False

DESCRIPTION

v.colors is much like r.colors, but may be used for vector maps. You give it a vector map and numeric data column, together with color rules like you would do for a raster. It creates a new column in the database with R:G:B values suitable for use with 'd.vect -a'.

How it works: it creates a dummy raster map with the same data range as the vector's column then runs r.colors for that temporary map. It then uses r.what.colors for each value found by v.db.select and uploads it a new column in the vector map's attribute database.

It is planned that this script will be replaced with a C display module which renders thematic vector maps directly instead requiring the overhead of saving the colors into the DB.

If the target column name given by the rgb_column option does not exist, it will be created. The default name is "GRASSRGB".

EXAMPLES

Create a random sample point map, query raster map values for those points, and colorize output.

# Spearfish dataset
g.region -d
v.random out=rand5k_elev n=5000
v.db.addtable map=rand5k_elev column='elevation double precision'
v.what.rast vector=rand5k_elev raster=elevation.10m column=elevation
v.colors map=rand5k_elev column=elevation color=bcyr

# display colorized points map
d.mon x0
d.vect -a rand5k_elev

Colorizing the roads map in Spearfish:

g.copy vector=roads,myroads
echo "1 red
2 yellow
3 orange
4 black
5 grey" > colors.txt

v.colors myroads column=cat rules=colors.txt

# display colorized roads map
d.mon x0
d.vect -a myroads

Colorizing a TIN (polygons) generated by v.delaunay:

# new columns for x,y,z of centroids
v.db.addtable map=tin \
   columns="east double precision, north double precision, height double precision, GRASSRGB varchar(11)"

# transfer geometry for colorizing (we need the centroid height)
v.to.db tin option=coor columns="east,north,height"
v.db.select tin

v.colors tin column=height rgb_column=GRASSRGB color=rainbow

# display colorized triangles
d.mon x0
d.vect -a tin

AUTHOR

Hamish Bowman
Dunedin, New Zealand

SOURCE CODE

Available at: v.colors2 source code (history)
Latest change: Thursday Feb 20 13:02:26 2025 in commit 53de819