[Geoserver-users] Add color-bar legend to SLD file

Greg_Cockroft · September 3, 2008, 5:09pm

Hi,

I have the following SLD file:

<?xml version="1.0" encoding="UTF-8"?>
<StyledLayerDescriptor xmlns="http://www.opengis.net/sld" xmlns:ogc="http://www.opengis.net/ogc" xmlns:xlink="http://www.w3.org/1999/xlink" xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance" xsi:schemaLocation="http://www.opengis.net/sld
http://schemas.opengis.net/sld/1.0.0/StyledLayerDescriptor.xsd" version="1.0.0">
<UserLayer>
  <Name>raster_layer</Name>
  <UserStyle>
    <Name>raster</Name>
    <Title>A boring default style</Title>
    <Abstract>A sample style for rasters</Abstract>
    <FeatureTypeStyle>
          <FeatureTypeName>Feature</FeatureTypeName>
      <Rule>
        <RasterSymbolizer>
          <ColorMap type="ramp" extended="true">
            <ColorMapEntry color="#FFFFFF" quantity="0.0" opacity="1.0"/>
            <ColorMapEntry color="#F0DBB8" quantity="1.0" opacity="1.0"/>
            <ColorMapEntry color="#B4FFAA" quantity="10.0" opacity="1.0"/>
            <ColorMapEntry color="#78EC73" quantity="25.0" opacity="1.0"/>
            <ColorMapEntry color="#3CD737" quantity="50.0" opacity="1.0"/>
            <ColorMapEntry color="#B4ECFA" quantity="75.0" opacity="1.0"/>
            <ColorMapEntry color="#78C7FA" quantity="100.0" opacity="1.0"/>
            <ColorMapEntry color="#3C96F6" quantity="150.0" opacity="1.0"/>
            <ColorMapEntry color="#1E6EEC" quantity="200.0" opacity="1.0"/>
            <ColorMapEntry color="#FFE878" quantity="300.0" opacity="1.0"/>
            <ColorMapEntry color="#FFA000" quantity="400.0" opacity="1.0"/>
            <ColorMapEntry color="#FF3200" quantity="600.0" opacity="1.0"/>
          </ColorMap>
          <Opacity>1.0</Opacity>
        </RasterSymbolizer>
      </Rule>
    </FeatureTypeStyle>
  </UserStyle>
</UserLayer>
</StyledLayerDescriptor>

I would like to add a simple color-bar legend to my OpenLayers maps. I believe that I can do this by adding a LegendGraphic element to the above XML, and then making a GetLegendGraphic request. I am having a hard time finding documentation on how to do this. Is there an example of how to use the LegendGraphic tag, and how to format the GetLegendGraphic request? If someone could provide one, I would be most grateful.

Thanks!

Greg

Alexander_Petkov · September 3, 2008, 5:12pm

I am interested in this as well. Currently I have my home-baked
sollution for adding a colorbar to a legend.

Alex

On Wed, Sep 3, 2008 at 11:09 AM, Greg Ederer <greg@anonymised.com> wrote:

Hi,

I have the following SLD file:

<?xml version="1.0" encoding="UTF-8"?>
<StyledLayerDescriptor xmlns="http://www.opengis.net/sld"
xmlns:ogc="http://www.opengis.net/ogc"
xmlns:xlink="http://www.w3.org/1999/xlink"
xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"
xsi:schemaLocation="http://www.opengis.net/sld
http://schemas.opengis.net/sld/1.0.0/StyledLayerDescriptor.xsd"
version="1.0.0">
<UserLayer>
<Name>raster_layer</Name>
<UserStyle>
   <Name>raster</Name>
   <Title>A boring default style</Title>
   <Abstract>A sample style for rasters</Abstract>
   <FeatureTypeStyle>
         <FeatureTypeName>Feature</FeatureTypeName>
     <Rule>
       <RasterSymbolizer>
         <ColorMap type="ramp" extended="true">
           <ColorMapEntry color="#FFFFFF" quantity="0.0" opacity="1.0"/>
           <ColorMapEntry color="#F0DBB8" quantity="1.0" opacity="1.0"/>
           <ColorMapEntry color="#B4FFAA" quantity="10.0" opacity="1.0"/>
           <ColorMapEntry color="#78EC73" quantity="25.0" opacity="1.0"/>
           <ColorMapEntry color="#3CD737" quantity="50.0" opacity="1.0"/>
           <ColorMapEntry color="#B4ECFA" quantity="75.0" opacity="1.0"/>
           <ColorMapEntry color="#78C7FA" quantity="100.0" opacity="1.0"/>
           <ColorMapEntry color="#3C96F6" quantity="150.0" opacity="1.0"/>
           <ColorMapEntry color="#1E6EEC" quantity="200.0" opacity="1.0"/>
           <ColorMapEntry color="#FFE878" quantity="300.0" opacity="1.0"/>
           <ColorMapEntry color="#FFA000" quantity="400.0" opacity="1.0"/>
           <ColorMapEntry color="#FF3200" quantity="600.0" opacity="1.0"/>
         </ColorMap>
         <Opacity>1.0</Opacity>
       </RasterSymbolizer>
     </Rule>
   </FeatureTypeStyle>
</UserStyle>
</UserLayer>
</StyledLayerDescriptor>

I would like to add a simple color-bar legend to my OpenLayers maps. I
believe that I can do this by adding a LegendGraphic element to the
above XML, and then making a GetLegendGraphic request. I am having a
hard time finding documentation on how to do this. Is there an example
of how to use the LegendGraphic tag, and how to format the
GetLegendGraphic request? If someone could provide one, I would be most
grateful.

Thanks!

Greg

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| greg@anonymised.com
| 360.774.6848
|

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Greg_Cockroft · September 5, 2008, 5:18am

Hi Kelly,

This is very helpful for feature legends. Thanks very much. I didn't know you could do this.

For my rasters, I'm writing a servlet that parses the SLD files and generates the color-bar legend. I may refactor this into a GeoServer plugin at some point. I only started this work because I received no response to the question below. I'd love to know if there is another way to do this, or if someone else working on this.

Cheers,

Greg

Kelly Sharp wrote:

I don't know if this will help but this how I've put tighter as a quick
solution for me

http://www.middakveg.com/bfid/map/

Kelly Sharp

-----Original Message-----
From: geoserver-users-bounces@lists.sourceforge.net
[mailto:geoserver-users-bounces@lists.sourceforge.net] On Behalf Of Greg
Ederer
Sent: Wednesday, September 03, 2008 12:10 PM
To: geoserver-users@lists.sourceforge.net
Subject: [Geoserver-users] Add color-bar legend to SLD file

Hi,

I have the following SLD file:

<?xml version="1.0" encoding="UTF-8"?>
<StyledLayerDescriptor xmlns="http://www.opengis.net/sld" xmlns:ogc="http://www.opengis.net/ogc" xmlns:xlink="http://www.w3.org/1999/xlink" xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance" xsi:schemaLocation="http://www.opengis.net/sld
http://schemas.opengis.net/sld/1.0.0/StyledLayerDescriptor.xsd" version="1.0.0">
<UserLayer>
  <Name>raster_layer</Name>
  <UserStyle>
    <Name>raster</Name>
    <Title>A boring default style</Title>
    <Abstract>A sample style for rasters</Abstract>
    <FeatureTypeStyle>
          <FeatureTypeName>Feature</FeatureTypeName>
      <Rule>
        <RasterSymbolizer>
          <ColorMap type="ramp" extended="true">
            <ColorMapEntry color="#FFFFFF" quantity="0.0" opacity="1.0"/>
            <ColorMapEntry color="#F0DBB8" quantity="1.0" opacity="1.0"/>
            <ColorMapEntry color="#B4FFAA" quantity="10.0" opacity="1.0"/>
            <ColorMapEntry color="#78EC73" quantity="25.0" opacity="1.0"/>
            <ColorMapEntry color="#3CD737" quantity="50.0" opacity="1.0"/>
            <ColorMapEntry color="#B4ECFA" quantity="75.0" opacity="1.0"/>
            <ColorMapEntry color="#78C7FA" quantity="100.0" opacity="1.0"/>
            <ColorMapEntry color="#3C96F6" quantity="150.0" opacity="1.0"/>
            <ColorMapEntry color="#1E6EEC" quantity="200.0" opacity="1.0"/>
            <ColorMapEntry color="#FFE878" quantity="300.0" opacity="1.0"/>
            <ColorMapEntry color="#FFA000" quantity="400.0" opacity="1.0"/>
            <ColorMapEntry color="#FF3200" quantity="600.0" opacity="1.0"/>
          </ColorMap>
          <Opacity>1.0</Opacity>
        </RasterSymbolizer>
      </Rule>
    </FeatureTypeStyle>
  </UserStyle>
</UserLayer>
</StyledLayerDescriptor>

I would like to add a simple color-bar legend to my OpenLayers maps. I believe that I can do this by adding a LegendGraphic element to the above XML, and then making a GetLegendGraphic request. I am having a hard time finding documentation on how to do this. Is there an example of how to use the LegendGraphic tag, and how to format the GetLegendGraphic request? If someone could provide one, I would be most grateful.

Thanks!

Greg

Andrea_Aime3 · September 8, 2008, 6:47am

Greg Ederer ha scritto:

Hi Kelly,

This is very helpful for feature legends. Thanks very much. I didn't know you could do this.

For my rasters, I'm writing a servlet that parses the SLD files and generates the color-bar legend. I may refactor this into a GeoServer plugin at some point. I only started this work because I received no response to the question below. I'd love to know if there is another way to do this, or if someone else working on this.

Not as far as I know. So your code does inspect the symbolizer and
builds dynamically a color bar? This would be very cool and could be
integrated into the GetLegendGraphics code

Cheers
Andrea

Greg_Cockroft · September 8, 2008, 4:37pm

Hi Andrea,

Exactly. This is currently implemented as a servlet, and is pretty crude (I needed it for a demo). It actually parses the info.xml file for the coverage, gets the default SLD file name, parses the SLD file and uses the ColorMap to produce the legend, then writes it out to the browser as an image/jpeg. It does not support any kind of caching.

I would eventually like to roll this into a GeoServer plugin, and add support for the full subset of the SLD schema that can influence legend composition.

Cheers,

Greg

Andrea Aime wrote:

Not as far as I know. So your code does inspect the symbolizer and
builds dynamically a color bar? This would be very cool and could be
integrated into the GetLegendGraphics code

Cheers
Andrea

Andrea_Aime3 · September 8, 2008, 4:41pm

Greg Ederer ha scritto:

Hi Andrea,

Exactly. This is currently implemented as a servlet, and is pretty crude (I needed it for a demo). It actually parses the info.xml file for the coverage, gets the default SLD file name, parses the SLD file and uses the ColorMap to produce the legend, then writes it out to the browser as an image/jpeg. It does not support any kind of caching.

I would eventually like to roll this into a GeoServer plugin, and add support for the full subset of the SLD schema that can influence legend composition.

Sounds great, minus the bit about the plugin, which I'm not sure about.
We don't have any pluggability in GetLegendGraphics and I'm not sure
we need any... I mean, it seems just a matter of adding your code creating a decent legend for raster symbolizer into the existing one, which at the moment does not know how to deal with raster symbolizer.

If/when you have a patch, just add it to jira.codehaus.org as a new
issue of type improvement. Oh, and if you need any help figuring
out the code, write us mails or ping us on irc (GeoServer at
irc.freenode.net)... I'm not very knowledgeable about that part
of GeoServer but I'll try to help out anyways.

Cheers
Andrea

Greg_Cockroft · September 8, 2008, 4:49pm

I'll have to take a look at the current implementation of GetLegendGraphics. I would like to be able to get the data I need to compose the color-bar from GeoServer's in-memory representation of the XML files. I'm not sure where those hooks are.

Cheers,

Greg

Andrea Aime wrote:

Greg Ederer ha scritto:

Hi Andrea,

Exactly. This is currently implemented as a servlet, and is pretty crude (I needed it for a demo). It actually parses the info.xml file for the coverage, gets the default SLD file name, parses the SLD file and uses the ColorMap to produce the legend, then writes it out to the browser as an image/jpeg. It does not support any kind of caching.

I would eventually like to roll this into a GeoServer plugin, and add support for the full subset of the SLD schema that can influence legend composition.

Sounds great, minus the bit about the plugin, which I'm not sure about.
We don't have any pluggability in GetLegendGraphics and I'm not sure
we need any... I mean, it seems just a matter of adding your code creating a decent legend for raster symbolizer into the existing one, which at the moment does not know how to deal with raster symbolizer.

If/when you have a patch, just add it to jira.codehaus.org as a new
issue of type improvement. Oh, and if you need any help figuring
out the code, write us mails or ping us on irc (GeoServer at
irc.freenode.net)... I'm not very knowledgeable about that part
of GeoServer but I'll try to help out anyways.

Cheers
Andrea

Simone3 · December 29, 2008, 9:16am

Resurrecting and old thread.
I am putting together an initial implementation of GetLegendGraphics for
raster data in GeoServer, therefore I would be interested in seeing this
code and possibly, in integrating it into my work.

Simone.

gederer wrote:

I'll have to take a look at the current implementation of
GetLegendGraphics. I would like to be able to get the data I need to
compose the color-bar from GeoServer's in-memory representation of the
XML files. I'm not sure where those hooks are.

Cheers,

Greg

Andrea Aime wrote:

Greg Ederer ha scritto:

Hi Andrea,

Exactly. This is currently implemented as a servlet, and is pretty
crude (I needed it for a demo). It actually parses the info.xml file
for the coverage, gets the default SLD file name, parses the SLD file
and uses the ColorMap to produce the legend, then writes it out to
the browser as an image/jpeg. It does not support any kind of caching.

I would eventually like to roll this into a GeoServer plugin, and add
support for the full subset of the SLD schema that can influence
legend composition.

Sounds great, minus the bit about the plugin, which I'm not sure about.
We don't have any pluggability in GetLegendGraphics and I'm not sure
we need any... I mean, it seems just a matter of adding your code
creating a decent legend for raster symbolizer into the existing one,
which at the moment does not know how to deal with raster symbolizer.

If/when you have a patch, just add it to jira.codehaus.org as a new
issue of type improvement. Oh, and if you need any help figuring
out the code, write us mails or ping us on irc (GeoServer at
irc.freenode.net)... I'm not very knowledgeable about that part
of GeoServer but I'll try to help out anyways.

Cheers
Andrea

--
| E R G O N O S I S
| Greg Ederer
| Lead Developer
| greg@anonymised.com
| 360.774.6848
|

-------------------------------------------------------------------------
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challenge
Build the coolest Linux based applications with Moblin SDK & win great
prizes
Grand prize is a trip for two to an Open Source event anywhere in the
world
http://moblin-contest.org/redirect.php?banner_id=100&url=/
_______________________________________________
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Piero_Campa · March 24, 2010, 6:08pm

Some news about this implementation?
Piero

Simone.Giannecchini wrote:

Resurrecting and old thread.
I am putting together an initial implementation of GetLegendGraphics for
raster data in GeoServer, therefore I would be interested in seeing this
code and possibly, in integrating it into my work.

Simone.

gederer wrote:

I'll have to take a look at the current implementation of
GetLegendGraphics. I would like to be able to get the data I need to
compose the color-bar from GeoServer's in-memory representation of the
XML files. I'm not sure where those hooks are.

Cheers,

Greg

Andrea Aime wrote:

Greg Ederer ha scritto:

Hi Andrea,

Exactly. This is currently implemented as a servlet, and is pretty
crude (I needed it for a demo). It actually parses the info.xml file
for the coverage, gets the default SLD file name, parses the SLD file
and uses the ColorMap to produce the legend, then writes it out to
the browser as an image/jpeg. It does not support any kind of caching.

I would eventually like to roll this into a GeoServer plugin, and add
support for the full subset of the SLD schema that can influence
legend composition.

Sounds great, minus the bit about the plugin, which I'm not sure about.
We don't have any pluggability in GetLegendGraphics and I'm not sure
we need any... I mean, it seems just a matter of adding your code
creating a decent legend for raster symbolizer into the existing one,
which at the moment does not know how to deal with raster symbolizer.

If/when you have a patch, just add it to jira.codehaus.org as a new
issue of type improvement. Oh, and if you need any help figuring
out the code, write us mails or ping us on irc (GeoServer at
irc.freenode.net)... I'm not very knowledgeable about that part
of GeoServer but I'll try to help out anyways.

Cheers
Andrea

--
| E R G O N O S I S
| Greg Ederer
| Lead Developer
| greg@anonymised.com
| 360.774.6848
|

-------------------------------------------------------------------------
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challenge
Build the coolest Linux based applications with Moblin SDK & win great
prizes
Grand prize is a trip for two to an Open Source event anywhere in the
world
http://moblin-contest.org/redirect.php?banner_id=100&url=/
_______________________________________________
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