Chart Plugin

The gt-chart plugin supports the definition of a Chart as a Mark or ExternalGraphic. This is implemented as a “dynamic symbolizer” using the JFreeChart and Eastwood projects.

References:

• http://www.jfree.org/eastwood/

• http://www.jfree.org/jfreechart/

Maven:

<dependency>
  <groupId>org.geotools</groupId>
  <artifactId>gt-charts</artifactId>
  <version>${geotools.version}</version>
</dependency>

Example

The following example is taken from test cases:

• streams.sld

• cities.properties

Here is the example SLD:

<?xml version="1.0" encoding="ISO-8859-1"?>
<StyledLayerDescriptor version="1.0.0"
	xsi:schemaLocation="http://www.opengis.net/sld http://schemas.opengis.net/sld/1.0.0/StyledLayerDescriptor.xsd"
	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">
	<NamedLayer>
		<Name></Name>
		<title></title>
		<abstract></abstract>
		<UserStyle>
			<Name>Pie charts</Name>
			<FeatureTypeStyle>
				<Rule>
					<PointSymbolizer>
						<Graphic>
							<ExternalGraphic>
								<OnlineResource xlink:href="http://chart?cht=p&amp;chl=male|female&amp;chd=t:${100 * male / (male + female)},${100 * female / (male + female)}&amp;chs=200x100&amp;chf=bg,s,FFFFFF00"/>
								<Format>application/chart</Format>
							</ExternalGraphic>
						</Graphic>
					</PointSymbolizer>
				</Rule>
			</FeatureTypeStyle>
		</UserStyle>
	</NamedLayer>
</StyledLayerDescriptor>

Configuration

Charts are configured by an URL of the form http://chart?key=value&key=value . In an SLD, the URL needs to be XML-encoded, so you’ll end up with xlink:href=”http://chart?key=value&key=valu&….”

Most keys have multiple arguments, whose name encodes the type: f= floating point, i= integer, c = color RRGGBB or RRGGBBAA

The chart plugin implements the URLs using Eastwood, an old and now-abandoned library based on JFreeCharts (last release is 2008). In turn, Eastwood implemented part of the Google Charts API, also now abandoned and replaced by a Javascript library.

The original Google documentation for these keys is thankfully saved in the Wayback Machine. Be patient, it’s slow and sometimes fails with a 500, but if you insist you’ll get to the page. https://web.archive.org/web/20080203131425/https://code.google.com/apis/chart Note how parameters from 2010 onwards are not implemented by this plugin.

The following keys are supported.

Supported keys for the chart URL

Key	Description
cht	Chart type - Supported values are: Value Resulting type Data series p Pie chart (1 series) 1 p3 3D Pie chart 1 lc Line chart n ls Sparkline chart n lxy XY Line chart 2n bhg Bar chart - Horizontal n bhs Bar chart - Horizontal - Stacked n bhs3 Bar chart - Horizontal - 3D n bvg Bar chart - Vertical n bvs Bar chart - Vertical -Stacked n bvg3 Bar chart - Vertical - 3D n s Scatter chart 2 (XY) or 3 (XYZ) dial Dial chart special v (Venn diagrams not implemented)
chco	Chart color - format is cColor1 ‘,’ cColor2 ‘,’ cColor3 …
chd	Data - can be formatted in 3 ways: simple/text/extended: Format ‘s:’ serie ‘,’ serie ‘,’ … Each serie contains characters A..Z,a..z,0..9 with A being the lowest 0.0 and 9 the highest possible value 1.0 Format ‘t:’ fValueSerie1 ‘,’ fValueSerie1 ‘,’ … ‘|’ fValueSerie2 ‘,’ … Format ‘e:’ serie ‘,’ serie ‘,’ … This is a high-precision variant of s: Each serie contains character pairs A..Z,a..z,0..9, -. with AA being the lowest 0.0 and .. the highest possible value 1.0 Dials have a special syntax: item ‘,’ item ‘,’ … Items are: Data range: ‘dr=’ fNumber ‘:’ fNumber ‘:’ cColor lower bound: ‘lb=’ fNumber upper bound: ‘ub=’ fNumber minor tick increment: ‘mt=’ fNumber major tick increment: ‘mjt=’ fNumber
chds	Data scaling - format is fScale ‘,’ fScale ‘,’ … This is an Eastwood extension, not part of Google Charts.
chf	Fill spec - format is spec ‘|’ spec Spec is one of: background color: ‘bgs’ cColor background linear gradient: ‘blg’ fAngle ‘,’ cColor0 ‘,’ f0 ‘,’ cColor1 ‘,’ f1 plot color: ‘cs’ cColor plot linear gradient: ‘clg’ fAngle ‘,’ cColor0 ‘,’ f0 ‘,’ cColor1 ‘,’ f1 Google Charts linear stripes are not supported
chg	Grid line spec - format is fXStep ‘,’ fYStep ‘,’ fLineSegLen ‘, ‘ fBlankSegLen
chl	Labels - format is label ‘|’ label …
chdl	Legend - format is label ‘|’ label …
chls	Line style - format is fWidth ‘,’ fLineRun ‘,’ fGapRun ‘|’ …
chm	Markers - format is type ‘,’ cColor ‘,’ (ignored) ‘,’ fStart ‘,’ fEnd ‘|’ … Types are ‘r’ for a range (Y-axis) marker, ‘R’ for a domain (X-axis) marker. Google Chart shape markers are not supported.
chp	Pie chart rotation - format is fAngle This is an Eastwood extension, not part of Google Charts.
chs	Chart size - format is iWidth ‘x’ iHeight ( in pixels)
chts	Axis title style - format is: cTitleColor ‘,’ iFontSize
chtt	Axis title - format is title ‘|’ title ‘|’ …
chxr	Axis range - format is: iAxisIndex ‘,’ fLowerBound ‘,’ fUpperBound ‘|’ …
chxl	Axis label - format is: iAxisIndex ‘:’ sText ‘|’ …
chxp	Axis label position - format is: iAxisIndex ‘,’ fTickNumber ‘,’ fTickNumber … ‘|’ …
chxs	Axis style - format is: iAxisIndex ‘,’ cAxisColor ‘,’ fFontsize ‘,’ unused ‘,’ drawingcontrol ‘,’ cTickColor ‘|’ … drawingcontrol is an Eastwood extension, not part of Google Charts., ‘l’ /’t’ / ‘_’ / ‘lt’ where l and t make tickmarks and axis line visible.
chxt	Axis text - format is: axis ‘,’ axis ‘,’ … axis is one of the characters ‘x’ ‘y’ ‘r’ ‘t’. Every axis defines a new numbered axisindex, starting from 0
ewd2	Extra dataset, format is the same as chd This is an Eastwood extension, not part of Google Charts.
ewlo	Orientations - format is: iAxisIndex ‘,’ orientation ‘|’ … orientation is ‘s’ / ‘u’ / ‘d’ for standard/up/down This is an Eastwood extension, not part of Google Charts.
ewtr	format is iSeries ‘,’ cColor ‘,’ cLineWidth This is an Eastwood extension, not part of Google Charts.