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NAME

       r.colors  - Creates/modifies the color table associated with a raster map.

KEYWORDS

       raster, color table

SYNOPSIS

       r.colors
       r.colors --help
       r.colors  [-rwldngae]  [map=name[,name,...]]   [file=name]   [color=style]   [raster=name]
       [raster_3d=name]   [rules=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

       -d
           List available rules with description then exit
           If a color rule is given, only this rule is listed

       -n
           Invert colors

       -g
           Logarithmic scaling

       -a
           Logarithmic-absolute scaling

       -e
           Histogram equalization

       --help
           Print usage summary

       --verbose
           Verbose module output

       --quiet
           Quiet module output

       --ui
           Force launching GUI dialog

   Parameters:
       map=name[,name,...]
           Name of raster map(s)

       file=name
           Input file with one map name per line
           Input map names can be defined in an input file in case a large amount of maps must be
           specified. This option is mutual exclusive to the map option.

       color=style
           Name of color table
           Options:  aspect, aspectcolr, bcyr, bgyr, blues, byg, byr, celsius, corine, curvature,
           differences, elevation, etopo2, evi, fahrenheit,  forest_cover,  gdd,  grass,  greens,
           grey,  grey.eq,  grey.log, grey1.0, grey255, gyr, haxby, inferno, kelvin, magma, ndvi,
           ndwi,   nlcd,   oranges,   plasma,   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 [range: map values]
            aspectcolr: aspect oriented rainbow colors [range: 0 to 360]
            bcyr: blue through cyan through yellow to red [range: map values]
            bgyr: blue through green through yellow to red [range: map values]
            blues: white to blue [range: map values]
            byg: blue through yellow to green [range: map values]
            byr: blue through yellow to red [range: map values]
            celsius: blue to red for degree Celsius temperature [range: -80 to 80]
            corine: EU Corine land cover colors [range: 111 to 995]
            curvature:  for  terrain  curvatures (from v.surf.rst and r.slope.aspect) [range: map
           values]
            differences: differences oriented colors [range: map values]
            elevation: maps relative ranges of raster values to elevation color ramp [range:  map
           values]
            etopo2: colors for ETOPO2 worldwide bathymetry/topography [range: -11000 to 8850]
            evi: enhanced vegetative index colors [range: -1 to 1]
            fahrenheit: blue to red for Fahrenheit temperature [range: -112 to 176]
            forest_cover: percentage of forest cover [range: 0 to 100]
            gdd: accumulated growing degree days [range: 0 to 6000]
            grass: GRASS GIS green (perceptually uniform) [range: map values]
            greens: white to green [range: map values]
            grey: grey scale [range: map values]
            grey.eq: histogram-equalized grey scale [range: map values]
            grey.log: histogram logarithmic transformed grey scale [range: map values]
            grey1.0: grey scale for raster values between 0.0-1.0 [range: 0 to 1]
            grey255: grey scale for raster values between 0-255 [range: 0 to 255]
            gyr: green through yellow to red [range: map values]
            haxby: relative colors for bathymetry or topography [range: map values]
            inferno: perceptually uniform sequential color table inferno [range: map values]
            kelvin: blue to red for temperature in Kelvin scale [range: 193.15 to 353.15]
            magma: perceptually uniform sequential color table magma [range: map values]
            ndvi: Normalized Difference Vegetation Index colors [range: -1 to 1]
            ndwi: Normalized Difference Water Index colors [range: -200 to 200]
            nlcd: US National Land Cover Dataset colors [range: 0 to 95]
            oranges: white to orange [range: map values]
            plasma: perceptually uniform sequential color table plasma [range: map values]
            population:  color table covering human population classification breaks [range: 0 to
           2e+09]
            population_dens: color table covering human population density classification  breaks
           [range: 0 to 1e+09]
            precipitation: precipitation color table (0..2000mm) [range: 0 to 7000]
            precipitation_daily: precipitation color table (0..1000mm) [range: 0 to 10000]
            precipitation_monthly: precipitation color table (0..1000mm) [range: 0 to 1000]
            rainbow: rainbow color table [range: map values]
            ramp: color ramp [range: map values]
            random: random color table [range: map values]
            reds: white to red [range: map values]
            roygbiv:  [range: map values]
            rstcurv: terrain curvature (from r.resamp.rst) [range: map values]
            ryb: red through yellow to blue [range: map values]
            ryg: red through yellow to green [range: map values]
            sepia: yellowish-brown through to white [range: map values]
            slope: r.slope.aspect-type slope colors for raster values 0-90 [range: 0 to 90]
            soilmoisture: soilmoisture color table (0.0-1.0) [range: 0 to 1]
            srtm:  color palette for Shuttle Radar Topography Mission elevation [range: -11000 to
           8850]
            srtm_plus: color  palette  for  Shuttle  Radar  Topography  Mission  elevation  (with
           seafloor colors) [range: -11000 to 8850]
            terrain:  global  elevation  color  table covering -11000 to +8850m [range: -11000 to
           8850]
            viridis: perceptually uniform sequential color table viridis [range: map values]
            water: water depth [range: map values]
            wave: color wave [range: map values]

       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
           "-" to read rules from stdin

DESCRIPTION

       r.colors allows the user to create and/or modify the color  table  for  a  raster  map  or
       several  raster maps at once.  The raster maps (specified on the command line by map or as
       file using an input file with one map name per line) must  exist  in  the  user’s  current
       mapset search path.

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

       The raster_3d option allows user to specify a 3D raster map name from which  to  copy  the
       color map.

       The  -e  flag  equalizes  the  original raster’s color table. It can preclude the need for
       grey.eq rule, when used as -e color=grey. Note however, that this will not yield  a  color
       table identical to color=grey.eq, because grey.eq scales the fraction by 256 to get a grey
       level, while -e uses it to interpolate the original color table.  If  the  original  color
       table  is  a  0-255  grey  scale, -e is effectively scaling the fraction by 255. Different
       algorithms are used. -e is designed to work with any color table, both the floating  point
       and the integer raster maps.

       The  -g  flag  divides  the raster’s grey value range into 100 logarithmically equal steps
       (where "step" is a rule with the same grey level for the start and  end  points).  It  can
       preclude  the  need for grey.log rule, when used as -g color=grey. Note however, that this
       will not yield a color table identical to color=grey.log. Different algorithms  are  used.
       Unlike  color=grey.log,  -g  is  designed  to  work  with  both floating point and integer
       rasters, without performance issues with large datasets,  of  any  original  color  table.
       Logarithmic  scaling  doesn’t  work  on  negative values. In the case when the value range
       includes zero, there’s no realistic solution.

       The -e and -g flags are not mutually exclusive.

       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.

       Color   table   types   aspect,   grey,  grey.eq  (histogram-equalized  grey  scale),  byg
       (blue-yellow-green), byr (blue-yellow-red), gyr  (green-yellow-red),  rainbow,  ramp,  ryg
       (red-yellow-green),  random, and wave are pre-defined color tables that r.colors knows how
       to create without any further input.

       In case several input raster maps are provided the range (min, max) of all  maps  will  be
       used  for  color table creation. Hence the created color table will span from the smallest
       minimum to the largest maximum value of all input raster maps and will be applied  to  all
       input raster maps.

       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 slope rule is defined as:
       0  255:255:255
       2  255:255:0
       5  0:255:0
       10 0:255 255
       15 0:0:255
       30 255:0:255
       50 255:0:0
       90 0:0:0

       This is designed for the slope map generated by r.slope.aspect, where the value is a slope
       angle between 0 and 90 degrees.

       Similarly, the aspectcolr rule:
       0 white
       1 yellow
       90 green
       180 cyan
       270 red
       360 yellow

       is  designed  for the aspect maps produced by r.slope.aspect, where the value is a heading
       between 0 and 360 degrees.

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

       Using  color  table  type  rules,  there are two ways to build a color table:  by category
       values and by "percent" values.

       To build a color table by category values’ indices, the user should determine the range of
       category  values  in  the  raster  map  with  which the color table will be used. Specific
       category values will then be associated with specific colors. Note that a color  does  not
       have  to  be  assigned  for every valid category value because r.colors will interpolate a
       color ramp to fill in where color specification rules have been left out.  The  format  of
       such a specification is as follows:
       category_value color_name
       category_value color_name
       .. ..
       .. ..
       category_value color_name
       end

       Each category value must be valid for the raster map, category values must be in ascending
       order and only use standard GRASS color names  (aqua,  black,  blue,  brown,  cyan,  gray,
       green, grey, indigo, magenta, orange, purple, red, violet, white, yellow).

       Colors  can  also  be  specified by color numbers each in the range 0-255. The format of a
       category value color table specification using color numbers instead of color names is  as
       follows:
       category_value red_number:green_number:blue_number
       category_value red_number:green_number:blue_number
       .. .. .. ..
       .. .. .. ..
       category_value red_number:green_number:blue_number
       end

       Specifying  a  color  table by "percent" values allows one to treat a color table as if it
       were numbered from 0 to 100. The format of a "percent" value color table specification  is
       the  same as for a category value color specification, except that the category values are
       replaced by "percent" values, each from 0-100,  in  ascending  order.  The  format  is  as
       follows:
       percent_value% color_name
       percent_value% color_name
       .. ..
       .. ..
       percent_value% color_name
       end

       Using  "percent"  value  color  table specification rules, colors can also be specified by
       color numbers each in the  range  0-255.  The  format  of  a  percent  value  color  table
       specification using color numbers instead of color names is as follows:
       percent_value% red_number:green_number:blue_number
       percent_value% red_number:green_number:blue_number
       .. .. .. ..
       .. .. .. ..
       percent_value% red_number:green_number:blue_number
       end

       Note that you can also mix these two methods of color table specification; for example:
       0 black
       10% yellow
       78 blue
       100% 0:255:230
       end

       To set the NULL (no data) color, use the "nv" (null values) parameter:
       0 black
       10% yellow
       nv white
       end

       To  set  the  color to used for undefined values (beyond the range of the color rules) use
       the "default" parameter:
       0 red
       1 blue
       default grey
       end

NOTES

       All color tables are stored in $GISBASE/etc/colors/. Further user-defined color tables can
       also  be stored in this directory for access from the color parameter or in a user defined
       directory.  See also r.colors.out for printing color tables easily to the terminal.

       The color table assigned to a raster map is stored in $GISDBASE/location/mapset/colr/.

EXAMPLES

       The below example shows how you can specify colors for a three category map, assigning red
       to  category  1, green to category 2, and blue to category 3. Start by using a text editor
       to create the following rules specification file (save it with the name rules.file):
       1 red
       2 green
       3 blue
       end

       The color table can then by assigned to map threecats by the following GRASS commands (two
       ways are available):
       # read input from stdin
       cat rules.file | r.colors map=threecats rules=-
       # read directly from file
       r.colors map=threecats rules=rules.file

       To  create  a  natural  looking  lookup  table (LUT) for true map layer elevation, use the
       following rules specification file. It  will  assign  light  green  shades  to  the  lower
       elevations  (first  20%  of  the LUT), and then darker greens (next 15%, and next 20%) and
       light browns (next 20%) for middle elevations, and darker browns  (next  15%)  for  higher
       elevations, and finally yellow for the highest peaks (last 10% of LUT).
       0% 0:230:0
       20% 0:160:0
       35% 50:130:0
       55% 120:100:30
       75% 120:130:40
       90% 170:160:50
       100% 255:255:100

       To invert the current rules:
       r.colors map=current_raster -n rast=current_raster

SEE ALSO

         d.colortable,  d.histogram, d.legend, r.colors.out r.colors.stddev, r.support, r.univar,
       v.colors, v.colors.out, r3.colors, r3.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

       Michael Shapiro and David Johnson
       Support for 3D rasters by Soeren Gebbert

SOURCE CODE

       Available at: r.colors source code (history)

       Accessed: unknown

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       © 2003-2022 GRASS Development Team, GRASS GIS 7.8.7 Reference Manual