Ubuntu Manpage: d.legend - Displays a legend for a 2D or 3D raster map in the active frame of the graphics monitor.

NAME

       d.legend  - Displays a legend for a 2D or 3D raster map in the active frame of the graphics monitor.

KEYWORDS

       display, cartography, legend

SYNOPSIS

       d.legend
       d.legend --help
       d.legend   [-vctnsfdbl]    [raster=name]     [raster_3d=name]    [title=string]    [title_fontsize=float]
       [lines=integer]   [thin=integer]   [units=string]   [labelnum=integer]   [label_values=float[,float,...]]
       [label_step=float]       [digits=integer]       [at=bottom,top,left,right]        [use=float[,float,...]]
       [range=min,max]     [color=name]     [font=string]    [fontsize=float]    [path=name]    [charset=string]
       [border_color=name]   [bgcolor=name]   [--help]  [--verbose]  [--quiet]  [--ui]

   Flags:
       -v
           Do not show category labels

       -c
           Do not show category numbers

       -t
           Draw legend ticks for labels

       -n
           Skip categories with no label

       -s
           Draw smooth gradient

       -f
           Flip legend

       -d
           Add histogram to smoothed legend

       -b
           Show background

       -l
           Use logarithmic scale

       --help
           Print usage summary

       --verbose
           Verbose module output

       --quiet
           Quiet module output

       --ui
           Force launching GUI dialog

   Parameters:
       raster=name
           Name of raster map

       raster_3d=name
           Name of 3D raster map

       title=string
           Legend title

       title_fontsize=float
           Title font size
           Default: Same as fontsize
           Options: 1-360

       lines=integer
           Number of text lines (useful for truncating long legends)
           Options: 0-1000
           Default: 0

       thin=integer
           Thinning factor (thin=10 gives cats 0,10,20...)
           Options: 1-1000
           Default: 1

       units=string
           Units to display after labels (e.g. meters)

       labelnum=integer
           Number of text labels for smooth gradient legend
           Options: 2-100
           Default: 5

       label_values=float[,float,...]
           Specific values to draw ticks

       label_step=float
           Display label every step

       digits=integer
           Number of digits after decimal point
           Options: 0-6

       at=bottom,top,left,right
           Size and placement as percentage of screen coordinates (0,0 is lower left)
           bottom,top,left,right
           Options: 0-100

       use=float[,float,...]
           List of discrete category numbers/values for legend

       range=min,max
           Use a subset of the map range for the legend (min,max)

       color=name
           Text color
           Either a standard color name or R:G:B triplet
           Default: black

       font=string
           Font name

       fontsize=float
           Font size
           Default: Auto-scaled
           Options: 1-360

       path=name
           Path to font file

       charset=string
           Text encoding (only applicable to TrueType fonts)

       border_color=name
           Border color
           Either a standard color name, R:G:B triplet, or "none"
           Default: black

       bgcolor=name
           Background color
           Either a standard color name, R:G:B triplet, or "none"
           Default: white

DESCRIPTION

       d.legend displays a legend for a user-specified raster map or 3D raster map layer in the active frame  on
       the graphics monitor.

       The  legend’s  default  size  is  based  on  the dimensions of the active frame, specifically its height.
       d.legend will only obscure those portions of the active frame that directly underlie the legend.

NOTES

When using the at to size & place the legend, a user may create a horizontal legend by making the box
wider than it is tall.

Raster maps based on floating point values will display smoothed, from greatest to smallest value, while
categorical raster maps will display in order, from top to bottom. Horizontal legends will always be
smoothed. If the box is defined with inverted y-values or an inverted range, the legend will
automatically flip. If this is not the desired result, the -f flag may be used to flip it back.

If the user attempts to display a very long legend in a relatively short display frame, the legend may
appear in unreadably small text, or even revert to a smooth gradient legend. Use the lines, thin, use,
range, and/or -n options to reduce the number of categories to be displayed, or the -s flag to force a
smooth gradient legend.

The lines option will display the first number of categories, as defined by value, contained in the
raster map. When used with the -n flag, it takes on a new meaning: "up to category #". When used with
both thin and the -n flag, its meaning becomes more obscure. When using lines, auto-scaled text similar
to "4 of 16 categories" will be placed at the bottom of the legend.

The thin option sets the thinning factor. For raster maps with a 0th category, thin=10 gives cats
[0,10,20,...]. For raster maps starting at category 1, thin=10 gives cats [1,11,21,...].

The use option lets the user create a legend made up of arbitrary category values.
e.g. use=1000,100,10,0,-10,-100,-1000

The range option lets the user define the minimum and maximum categories to be used in the legend. It may
also be used to define the limits of a smooth gradient legend created from a raster containing floating
point values. Note the color scale will remain faithful to the category values as defined with r.colors,
and the range may be extended to the limits defined by the r.colors color map.

The flag -n is useful for categorial maps, as it suppresses the drawing of non-existing categories
(otherwise the full range is shown).

Vertical legends produced with d.legend will place text labels to the right of the legend box, horizontal
legends will place text below. This text will be auto-scaled to fit within the frame, reducing the size
of the legend if necessary. Legends positioned with the at option will not auto-scale text, in order to
provide more control to the user. Smaller text may be obtained in this case by reducing the height of
the box or by using the fontsize option. The -c and -v flags may be used to suppress the display of
category numbers and labels respectively, or used together to suppress all text of categorial raster
maps.

The text produced from floating-point raster maps will automatically create output with a meaningful
number of significant digits. For very small values, numbers will be expressed in scientific notation,
e.g. "1.7e-9". Option digits can be used to determine how many digits after decimal point will be
displayed.

When the -d flag is used to display a histogram distribution along side the smoothed gradient legend,
note that the statistics are calculated on the current computational region settings set by g.region.
The default range however covers the entire natural bounds of the input map. If the histogram appears
empty, check your region settings.

If the raster map’s units metadata has been set with the r.support module then it will be displayed along
side the legend.

The option title will display the custom title at the top of the legend. In case of vertical legend the
title is aligned to the left edge of legend, in case of horizontal legend the title is aligned to the
center. title_fontsize can be used to set the size of legend title. By default the legend title font size
is the same as labels font size.

There are different options to customize displayed labels. The labelnum set the number of labels which
are displayed in regular intervals. The label_values will specify the values where the labels will be
displayed. The label_step will display labels at values which are divisible by this value.

The flag -t will show ticks at labels.

The flag -b will show the background. Options bgcolor and border_color can be used to choose the color of
border and background fill.

The flag -l will switch to logarithmic scale. In case this flag is used, the provided step in label_step
is interpreted in the logarithmic space.

EXAMPLE

       Displaying the legend along with a histogram (North Carolina Sample dataset):
       g.region raster=elevation -p
       d.rast elevation
       d.legend -d elevation
       Displaying the legend with custom labels and background:
       g.region raster=elevation -p
       d.rast elevation
       d.legend raster=elevation -t label_step=20 label_values=108 title=Legend -b bgcolor=255:255:204 border_color=gray
       Displaying the legend with logarithmic scale:
       g.region raster=elevation -p
       r.watershed -a elevation=elevation threshold=1000 accumulation=flowacc
       d.rast flowacc
       d.legend raster=flowacc -t -l label_step=1

AUTHORS

       Bill Brown, U.S. Army Construction Engineering Research Laboratories
       Late 2002: Rewrite of much of the code. Hamish Bowman, Otago University, New Zealand
       Additional improvements from various authors

SOURCE CODE

       Available at: d.legend source code (history)

       Accessed: Friday Apr 04 01:18:48 2025

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       © 2003-2025 GRASS Development Team, GRASS GIS 8.4.1 Reference Manual

GRASS 8.4.1                                                                                     d.legend(1grass)