Describes how to create data source objects for vector and raster data sources.

A data source is an object that connects a feature iterator, a renderer, and a map layer.

A data source uses the feature iterator to get global data information, such as the coordinate system and bounding box, and the list of map features to parse. Then it uses the renderer to create graphic objects. Finally, it uses the layer to manage the order and style of those objects.

In class terms, a data source is a class that connects an IlvMapReusableFeatureIterator, an IlvFeatureRenderer and an IlvMapLayer. It uses the iterator object to get global data information, such as the coordinate system and bounding box, and the list of IlvMapFeature objects to parse. Then it uses the renderer object to create graphic objects. Finally it uses the layer object to manage the order and style of the graphic objects.

The source code for the Map Builder demonstration, which contains all of the code described in this section, can be found at <installdir> /jviews-maps/samples/mapbuilder/index.html

ESRI shapefile

When you create a Shapefile format data source the shapefiles can be loaded with or without the tiling mechanism. When using tiling, the data is loaded in a background thread.

The complete source code for an ESRI shapefile demonstration can be found at <installdir> /jviews-maps/shape/mapbuilder/index.html

Loading a shapefile using tiling

To load a shapefile using tiling, use the following code:

If the shapefile does not have a tiling index file, you can create the index file as follows:

The resulting index file, which is used in the reader, can be set with a call to:

Loading a shapefile without using tiling

To load a shapefile without using tiling, use the following code:

MID/MIF

To create a MID/MIF file data source, use the following code:

TIGER/Line

To create a TIGER/Line data source, use the following code:

TIGER/Line® data contains many different features. You can select the features to import into your map by choosing the CFCC codes of the features you want:

DXF (AutoCAD)

The DXF format (Drawing Interchange Format) is the interchange format for AutoCAD. This format supports vector graphics (polygons, arcs, lines, points...) and layers.

The specifications of the various releases of the DXF format can be found at the following URL: http://usa.autodesk.com/adsk/servlet/item?siteID=123112&id=5129239.

For details of the limitations with a DXF data source, refer to Drawing Exchange Format (DXF) in the section on managers in The Essential JViews Framework.

To create a DXF data source, use the following code:

You must then set up the transformation you want to use to read DXF.

If you want to transform the DXF extent into the latitude/longitude range provided, call:

If you want to use a more complex transformation (such as reprojection), call:

An example of how to create a complex transformation is given in the Map Builder demonstration, through use of the DXFControlModel class.

KML or KMZ

KML/ KMZ is an XML-based numerical map format containing both vectorial and raster information. KML is published by Google™, for use in their Google Earth© Product.

You can find more information at http://earth.google.com/kml/kml_intro.html.

JViews Maps supports import of the KML elements shown in KML element support:

KML files can refer to other files, either locally or through a network link URL. KMZ is a compressed file containing a single doc.xml entry and a set of auxiliary files, such as images or icons.

To create a KML data source, use the following code:

SVG

SVG (Scalable Vector Graphic) is a language for describing two-dimensional graphics and graphical applications in XML. The specifications of the SVG format can be found at http://www.w3.org/Graphics/SVG.

The JViews Maps SVG reader is based on features in Rogue Wave® JViews Framework. These features are described in the section on Scalable Vector Graphics in The Advanced JViews Framework.

The JViews Maps SVG reader ignores the following SVG elements:

All the other elements, including text elements, are transformed into IlvMapGeneralPath instances.

The graphic styles in the resulting map are rendered to look as close as possible to the original version. However, the styles created are limited to the data available for styling such an object.

To create an SVG data source, use the following code:

You then need to set up the transformation you want to use to read SVG. To transform the SVG extent into the latitude/longitude range provided, call:

To use a more complex transformations such as reprojection, call:

An example of how to create a complex transformation using of the ControlModel example class can be found at <installdir> /jviews-maps/samples/mapbuilder/index.html

The source code for the Map Builder demonstration, which contains all of the code described in this section, can be found at <installdir> /jviews-maps/samples/mapbuilder/index.html

All raster (image) data sources have a common API. To create your data source, you need to create an IlvRasterAbstractReader for the type of data to be read, and then use this reader to build a tiled image data source.

Raster reader classes

The raster reader classes for the different image formats are as follows.

(*) Non georeferenced images must be geo-referenced, see Georeferencing a nongeoreferenced image.

Creating a raster reader

To create a raster reader and add all image files to be read you can, for example, use the following code:

Creating a tiled data source

To create a data source for the reader:

The IlvTiledRasterDataSource returned by the IlvRasterDataSourceFactory executes image reading in a background thread.

Georeferencing a nongeoreferenced image

To georeference a nongeoreferenced image, you can set the longitude and latitude image bounds:

Alternatively, you can compute a more complex mathematical transformation and set it on the reader:

Images from OpenGIS-compliant Web Map Servers

This section gives information about the OpenGIS® Web Map Server (WMS standard). This International Standard specifies the behavior of a service that produces spatially referenced maps dynamically from geographic information. It specifies operations to retrieve a description of the maps offered by a server and to query a server about features displayed on a map. The standard is not applicable to the retrieval of actual feature data or coverage data values, but is applicable to pictorial renderings of maps in a graphical format. These capabilities are provided by a Web Feature and Web Coverage Service.

In a basic WMS, only a limited number of predefined styles can be applied to features. The mechanism that enables users to define their own styles is defined in the OGC Styled Layer Descriptor Implementation Specification. An SLD-enabled WMS retrieves feature data from a Web Feature Service and applies explicit styling information provided by the user in order to render a map.

The ISO/TC 211 also defines a standard for Web Map Servers, see ISO 19128.

Importing a WMS image

JViews Maps supports the import of images from a WMS server.

To create a WMS data source, use the following code: