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Render FAQ

How do I display a shapefile?

Have a look at Tutorials which provides a quickstart showing how to do this.

Q: What is SLD?

Style Layer Descriptor Specification (SLD) is an OGC standard defining styles used when drawing maps. Think of it as CSS for maps.

GeoTools rendering is based around the Style Layer Descriptor standard, for details please see the gt-opengis module.

This standard is divided into two parts:

  • Style Layer Descriptor 1.1 covers the integration of styles with a web map server.
  • Symbology Encoding 1.1 covers the definition of a feature type style controlling how a rendering engine draws features.

Q: What is a MapContent?

A MapContent object holds one or more Layers which are rendered in the order that they were added.

This is not part of the formal gt-opengis module because it is not considered finished, done, or complete. The GeoTools community is actively looking to collaborate with other projects (such as OpenJUMP, uDig and deegree) in order to collaborate on these ideas. If open source collaboration fails we will look to traditional collaboration with a standards body in the form of the the OGC working group on “Open Web Context” documents.

Q: What about the Widget?

This module only draws into a Graphics2D context (so printer or image buffer). You can use this functionality in your own Swing widget in order to draw something on screen.

  • gt-swing

    GeoTools does not provide comprehensive GUI components but there is a basic Swing widget JMapFrame in the gt-swing module which is used in GeoTools example code. This can be used directly in your applications or it could form the starting point for writing your own Swing components. See JMapFrame for more details.

  • gt-swt

    The gt-swing JMapFrame has been ported to an SWT widget as an unsupported module.

  • udig

    uDig is an application and SDK built around the Eclipse platform, please consider this a real world solution suitable for desktop applications. It makes use of the SWT toolkit so while you can use it as an example of how to do really fast rendering you will not be able to directly use the code in a swing application.

Q: What about Raster Advanced Projection Handling?

Advanced Projection Handling is a feature provided by the GridCoverageRenderer class for handling Raster reprojection. It is especially useful when trying to read a GridCoverage with a BoundingBox crossing the DateLine: the final image is not cut on the DateLine but it is replicated as many times as the DateLine is crossed.

This feature can be enabled/disabled using the related method setAdvancedProjectionHandlingEnabled() in the same class.

Q: Why does my SVG external graphic display as a gray square?

GeoTools uses a plugable External Graphics factory system to render an icon (see Icon for more details) onto the screen. To render SVG files as icons it needs access to the SVGExternalGraphics factory which is included in the SVG Plugin.