/**
* This method returns a list of urls for retrieving the individual layers of the map. It will
* coalesce adjacent layers into a single request, when possible.
*
* @param layerList Element parent node to the list of layer Elements within the ViewContext
* @param layers String[] of layer names
* @param bbox Envelope spatial extent of the map image
* @param width x-dimension of the map image
* @param height y-dimension of the map image
* @param format String mime-type of the map image
* @return List of urls for get map requests
* @ssdd
*/
private List<String> getLayerRequests(
Element layerList, String[] layers, Envelope bbox, int width, int height, String format) {
List<String> requests = new ArrayList<String>();
String lastServer = null;
for (Element elem : DOMUtils.getChildren(layerList, "Layer")) {
// get layer name
String name = DOMUtils.getChildText(elem, "Name");
// is layer in list of requested layers?
if (!contains(layers, name)) continue;
// is layer visible?
if (Coerce.toBoolean(elem.getAttribute("hidden"))) continue;
// get href to layer's service
Node server = DOMUtils.getChild(elem, "Server");
Element or = DOMUtils.getChild(server, "OnlineResource");
String href = or.getAttribute("xlink:href");
if (href.equals(lastServer)) {
String layerNames = requests.remove(requests.size() - 1);
layerNames += "," + name;
requests.add(layerNames);
} else {
lastServer = href;
requests.add(getMapRequest(href, name, bbox, width, height, format));
}
}
return requests;
}
/**
* This method renders the <code>layers</code> from the <code>viewContext</code> into an image of
* the specified <code>width</code> and <code>height</code> contrained by the <code>bbox</code>.
*
* @param viewContext Node root node in ViewContext document
* @param bbox Envelope spatial extent of map
* @param width int x-dimension of map image
* @param height int y-dimension of map image
* @param format String mimetype of resulting map image and propogated to the map services
* providing each component layer.
* @return Image composited map image
* @throws Exception
* @ssdd
*/
public Image render(
Element viewContext, String[] layers, Envelope bbox, int width, int height, String format)
throws Exception {
String formatType = format.substring(format.indexOf("/") + 1, format.length());
BufferedImage image = createImage(formatType, width, height, true);
Dimension2D window = new Dimension(width, height);
Graphics2D graphics = (Graphics2D) image.getGraphics();
AffineTransform t = ProjectionUtility.total(window, bbox);
graphics.setTransform(t);
graphics.setColor(BACKGROUND_COLOR);
Element layerList = DOMUtils.getChild(viewContext, "LayerList");
List<String> requests = getLayerRequests(layerList, layers, bbox, width, height, format);
for (String url : requests) {
fetchImage(url, graphics); // retrieve map image
image.flush();
}
return image;
}