Geografic-Information-System/display/d.legend/d.legend.html

<h2>DESCRIPTION</h2>

<em>d.legend</em> displays a legend for a user-specified
raster map layer in the active frame on the graphics
monitor.  
<p>
The user can run <em>d.legend</em> either non-interactively
or interactively.  If the user specifies the name of a
raster <b>map</b> layer on the command line, the program
will run non-interactively.  Default legend text
<b>color</b> and position will be used unless
the user specifies other values on the command line.

<p>
Alternately, the user can simply type <b>d.legend</b> on the command line; 
in this case, the program will prompt the user for parameter values 
using the standard GRASS GUI interface.

<h2>NOTES</h2>

The legend's default size is based on the dimensions of the
active frame, specifically its height.  <em>d.legend</em> will only
obscure those portions of the active frame that directly underlie the legend.
<p>When using the mouse or <b>at</b> to size &amp; place the legend, a user may
create a horizontal legend by making the box wider than it is tall.
<p>Raster maps based on floating point values will display smoothed, from greatest
to smallest value, while categorial 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 <b>range</b>, the legend will automatically
flip. If this is not the desired result, the <b>-f</b> flag may be used to flip
it back.
<p>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 <b>lines</b>, <b>thin</b>, <b>use</b>, <b>range</b>,
and/or <b>-n</b> options to reduce the number of categories to be displayed,
or the <b>-s</b> flag to force a smooth gradient legend. 
Additionally the fonts for smoothed floating point legends
can be scaled by a scale factor <b>fontscale</b>, to adjust the automatically computed size of the legend font.
<p>The <b>lines</b> option will display the first number of categories, as defined
by <em>value</em>, contained in the raster map. When used with the <b>-n</b> flag,
it takes on a new meaning: "up to category #". When used with both
<b>thin</b> and the <b>-n</b> flag, its meaning becomes more obscure. When
using <b>lines</b>, auto-scaled text similar to "4 of 16 categories" will be placed at 
the bottom of the legend.
<p>The <b>thin</b> option sets the thinning factor. For raster maps with a 0th
category, <b>thin=</b><em>10</em> gives cats [0,10,20,...]. For raster maps 
starting at category 1, <b>thin=</b><em>10</em> gives cats [1,11,21,...].
<p>The <b>use</b> option lets the user create a legend made up of arbitrary category
values. e.g.&nbsp;<b>use=</b><em>1000,100,10,0,-10,-100,-1000</em>
<p>The <b>range</b> 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
<em><a href="r.colors.html">r.colors</a></em>, and the <b>range</b> may be
extended to the limits defined by the <em><a href="r.colors.html">r.colors</a></em>
color map.
<p>The flag <b>-n</b> is useful for categorial maps, as it suppresses the
drawing of non-existing categories (otherwise the full range is shown).
<p>Vertical legends produced with <em>d.legend</em> 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 mouse or with the <b>at</b> 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. The <b>-c</b> and <b>-v</b> 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.
<p>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.&nbsp;"1.7e-9".
<p>Legends placed with the mouse are not saved to the display window's history
for automatic redraw. By setting the Debug level to 1 (see 
<em><a href="g.gisenv.html">g.gisenv</a></em>) the corresponding <b>at</b>
setting can be determined.
<p>Note that old scripts which relied on setting <b>lines</b> greater than the
number of categories to scale the legend may no longer produce the desired
output, although the auto-scaling should still produce something that looks 
good in this case.

<h2>SEE ALSO</h2>

<em>
<a href="d.barscale.html">d.barscale</a>,
<a href="d.colortable.html">d.colortable</a>,
<a href="d.erase.html">d.erase</a>,
<a href="d.font.html">d.font</a>,
<a href="d.grid.html">d.grid</a>,
<a href="d.rast.html">d.rast</a>,
<!-- <a href="d.rast.labels.html">d.rast.labels</a>, -->
<a href="d.rast.leg.html">d.rast.leg</a>,
<a href="d.text.html">d.text</a>,
<a href="d.vect.thematic.html">d.vect.thematic</a>,
<!--<a href="d.what.rast.html">d.what.rast</a>,-->
<a href="r.reclass.html">r.reclass</a>
</em>

<h2>AUTHORS</h2>
Bill Brown, U.S. Army Construction Engineering Research Laboratories
<br>Late 2002: Rewrite of much of the code. Hamish Bowman,
 Otago University, New Zealand
<br>Additional improvements from various authors

<p>
<i>Last changed: $Date$</i>