NAME
v.colors2 - Sets color rules for features in a vector map using a numeric attribute column.
KEYWORDS
vector,
color table
SYNOPSIS
v.colors2
v.colors2 --help
v.colors2 [-sn] map=name [layer=string] column=name [rgb_column=name] [range=min,max] [color=string] [raster=name] [rules=name] [--help] [--verbose] [--quiet] [--ui]
Flags:
- -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
- --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
- 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
- Options: 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
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".
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
d.vect,
r.colors,
r.colors.stddev,
r.what.color,
v.db.addcolumn,
v.db.select,
db.execute
Hamish Bowman
Dunedin, New Zealand
SOURCE CODE
Available at:
v.colors2 source code
(history)
Latest change: Thursday Feb 03 09:32:35 2022 in commit: f17c792f5de56c64ecfbe63ec315307872cf9d5c
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