Map layers and map styles

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.

About map layers

The IlvMapLayer class represents a map layer, that is, a cartographic theme. It associates a style ( IlvMapStyle or one of its subclasses) with an IlvManagerLayer containing graphic objects.

Map Layers are arranged in a tree structure, and stored in the manager using the IlvMapLayerTreeProperty, see Map layer tree.

Each map layer is attached to an IlvMapLayerTreeNode, which contains the necessary information on parent and child layers. You can use this node to step through layer hierarchy as follows:

String SVGpath = "C:/maps/map.svg";

IlvSVGDataSource source = new IlvSVGDataSource(SVGpath);

source.setManager(getView().getManager());

source.setDestinationBounds(lonMinRad,latMinRad,lonMaxRad,latMaxRad);

Note

Alternatively you can use a tailored transformation by calling IlvSVGDataSource.setInternalTransformation.

source.start();

IlvMapLayerTreeNode node = mapLayer.getNode();

for (int i = 0; i < node.getChildCount(); i++) {

IlvMapLayerTreeNode child=(IlvMapLayerTreeNode) node.getChildAt(i);

IlvMapLayer childLayer = (IlvMapLayer) node.getUserObject();

... do something with child layer

}

Most map layers are attached to a data source, which is responsible for populating the manager layer with the correct graphic objects when the map data is loaded (possibly on-demand-loading) and reprojection times. The exception to this rule is the composite layer. Composite layers are only used to group a set of sub-layers and manage their styles using attribute inheritance (See below).

About map styles

Every style in JViews Maps is a subclass of the base IlvMapStyle class.

This class provides access to a set of attributes, usually also accessible by a setter/getter pair, depending on each style subclass.

For example, you can change the view visibility setting using on of:

style.setAttribute(IlvMapStyle.VISIBLE_IN_VIEW,Boolean.TRUE);

style.setVisibleInView(true);

You can catch any change in the map style by writing and registering a listener on it. For example:

StyleListener listener = new StyleListener() {

public void styleChanged(StyleEvent event) {

if(IlvMapStyle.ALPHA.equals(event.getAttribute())) {

// ... do something when transparency changes

}

};

...

myStyle.addStyleListener(listener);

Style hierarchy

Styles form a hierarchy and attribute values can be inherited through this hierarchy. If a style attribute is inherited from a parent style, that parent attribute value is used when displaying objects using that style.

Although not enforced in the API, it is recommended that you make the style hierarchy the same as the map layer hierarchy. This can be done when the map layer is inserted in the layer tree model:

IlvMapLayerTreeModel ltm =

IlvMapLayerTreeProperty.GetMapLayerTreeModel(manager);

ltm.addChild(parentLayer, layer);

IlvMapStyle parentStyle = layer.getParent().getStyle();

IlvMapStyle childStyle = layer.getStyle();

childStyle.setParent(parentStyle);

Common styling properties

Whatever the type of layer, its style always has the following base properties.

Common Styling Properties
Property name	Contents
VISIBLE_IN_VIEW	Indicates whether the IlvManagerLayer is displayed on the map view.
VISIBLE_IN_OVERVIEW	Indicates whether the IlvManagerLayer is displayed on the map overview.
ATTRIBUTE_INFO	Contains the IlvAttributeInfoProperty used to describe all object properties. This is used to provide the list of possible property names displayed in the label attribute check box. This attribute cannot be changed by the user in the map layer tree panel.
LABEL_ATTRIBUTE	Contains either a null value, or the name of the property used when labeling this map layer (chosen usually in the list provided by the ATTRIBUTE_INFO attribute).
ALWAYS_ON_TOP	Indicates whether the attached map layer is placed on a normal or superimposing plane. This should be used only for overlay layers such as grids, labels, measures, and so on.
LEGEND_GROUP	A logical name, used and displayed to group map layers in the legend.
CATEGORY	An identifying name to group more than one layer on the same legend line.
ALPHA	The level of transparency of the manager layer.

Map layers for graphic objects

The class diagram for map layers for graphic objects is shown in Layers for Graphic Objects UML Diagram.

Layers for Graphic Objects UML Diagram

Most map layers are used to manage graphic objects created from map features imported from various map data files. The styling options differ according to the content of each file and the map features imported by the different readers. For example, you do not style a polygon the same way you do an altitude raster image.

The IlvGeneralPathStyle class

The IlvGeneralPathStyle class is used for IlvMapGeneralPath stylable graphic objects. Generally, most vectorial map renderers provide a setUsingGeneralPath method to allow a choice between using general paths, which give a better aspect and capabilities, or regular polygons, which provide better performance.

General Path Styling Properties
Property name	Content
FILL_PAINT	Paint object used to fill the shape.
STROKE_PAINT	Paint object used when stroking the path.
FILL_ON	Boolean indicating whether the inside of the object is filled.
STROKE_ON	Boolean indicating whether the shape of the object is stroked.
PAINT_ABSOLUTE	Boolean indicating whether the fill paint is adapted to the bounding rectangle of the object.
STROKE_WIDTH	Stroke width.
PAINT_ZOOMED	Boolean indicating whether the paint is zoomed according to the shape when the object is zoomed.
END_CAP	Type of decoration applied to the ends of unclosed subpaths (see java.awt.BasicStroke ).
LINE_JOIN	Type of decoration applied at the intersection of two path segments (see java.awt.BasicStroke ).
LINE_STYLE	Float table indicating how to make a dash pattern by alternating between opaque and transparent sections (see java.awt.BasicStroke ).
STROKE	Object used for stroking the path. This attribute is dependant on all stroke attributes and is recomputed when one of them changes.This attribute is not visible in the Map Layer Tree Panel.

The IlvPolylineStyle class

The IlvPolylineStyle class is used for IlvMapPolyline stylable objects (polygons or polylines without fill).

Polyline Styling Properties
Property name	Content
FOREGROUND	Color object used when drawing the polygon borders.
LINE_WIDTH	Polygon borders line width.
END_CAP	Type of decoration applied to the ends of unclosed subpaths (see java.awt.BasicStroke ).
LINE_JOIN	Type of decoration applied at the intersection of two path segments (see java.awt.BasicStroke ).
LINE_STYLE	Float table indicating how to make a dash pattern by alternating between opaque and transparent sections (see java.awt.BasicStroke ).
DECORATION	Additional IlvPathDecoration object used for stroking the polygon.
DECORATION_ONLY	Boolean indicating whether only the decoration is displayed.
DECORATION_PAINT	Paint color of the decoration. By default (when this attribute is null), the decoration is colored using the FOREGROUND attribute.

The IlvGraphicPathStyle class

The IlvGraphicPathStyle class is a subclass of IlvPolylineStyle and so provides all the attributes in The IlvPolylineStyle class. It provides the style for IlvMapGraphicPath objects (filled polygon areas), by adding:

Graphic Path Styling Properties
Property name	Content
PAINT	Paint object used to fill the polygon area.
DO_FILL	Boolean indicating whether the inside of the polygon is filled.
DO_STROKE	Boolean indicating whether the borders of the polygon are stroked.

The IlvPointStyle class

The IlvPointStyle class controls the style of map point ( IlvMapPoint) objects. It provides the following attributes:

Point Styling Properties
Property name	Content
FOREGROUND	Color object used for displaying the point.
MARKER_SIZE	The size of the marker.
MARKER_TYPE	The type of marker to use.

The IlvMapTextStyle class

The IlvMapTextStyle class controls the style of map stylable label objects ( IlvMapText). It provides the following attributes:

Map Text Styling Properties
Property name	Content
ANTIALIASING	Boolean indicating whether text should be specifically antialiased (even if the view setting itself is different).
ATTACHMENT	The label attachment.
FILL_PAINT	Paint object used to fill the characters of the text.
FONT	The label Font.
FRAME_PAINT	Paint object used to draw the frame of the label.
INNER_MARGIN	Spacing between the frame of the label and the text.
INTERLINE	Spacing between two lines of text.
MAXIMUM_HEIGHT	The maximum height of the label.
MINIMUM_HEIGHT	The minimum height of the label.
STROKE_PAINT	Paint object used to draw the shape of the text character.
BACKGROUND_PAINT	Paint object used to fill the frame of the label.
ALIGNMENT	Alignment of the multi-line text.

The IlvRasterStyle class

The IlvRasterStyle class is used with IlvRasterIcon graphic objects, and provides attributes to control the appearance of the image:

Raster Styling Properties
Property name	Content
BRIGHTNESS	A Double percentage applied to the color model to make the entire image brighter or darker. 0% gives a black image.
CONTRAST	A Double percentage applied to the color model to increase the color difference. 0% gives a completely grey image.
SATURATION	A Double percentage applied to the color model of the image to change the color saturation. 0% gives a completely grey image.
COLOR_MODEL	The ColorModel object used to transform the pixel values of the image into RGBA colors.

Composite layers

The IlvMapCompositeStyle class

The IlvMapCompositeStyle class does not define any additional attributes. Its attribute list grows with its child list.

When adding a child style in a composite style, all the attributes of that child are added (if they did not exist) into the parent style. Those values can then be inherited for each child style – allowing the attributes for all children to be changed in one single place.

You can change the inheritance setting of each attribute by calling the setInherited method.

Label layer

Label layers are created automatically on demand by the IlvMapLabeler property installed on the manager when the LABEL_ATTRIBUTE style attribute is changed on a registered layer.

The IlvMapLabelStyle class

The IlvMapLabelStyle class is used by the IlvMapAreaLabel, IlvMapLineLabel and IlvMapPointLabel classes, and controls the labeling parameters:

Map Label Styling Properties
Property name	Content
FOREGROUND	The Color used to display labels.
LABEL_FONT	The Font of the labels.
LABEL_STROKE	The Stroke object used to display label outlines (not visible to users).
OUTLINE_COLOR	The Color of the label outline.
DRAW_OUTLINE	Boolean indicating whether the outline is displayed.
LABELLING_SMALL_AREAS	Boolean indicating whether areas too small to enclose their label are labeled.
FOLLOW_PATH	Boolean indicating whether labels on polygons follow those polygons or are placed horizontally.

Grid layers

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.

The IlvAbstractBaseGrid class

The IlvAbstractBaseGrid base class has subclasses IlvMGRSGrid and IlvLatLonGrid. It is a manager layer that, instead of drawing graphic objects ( IlvGraphic instances) added to it, displays a grid adapted to the current zoom level of the map.

This base grid also implements the IlvManagerViewDecoration interface, which allows you to display the grid on the screen, but prevents it from being displayed on printed material.

The IlvMGRSGrid class

The IlvMGRSGrid class displays a set of auto-adaptive MGRS standard grids and labels on top of a geographic view. This grid displays a list of Grid zones (either UPS or UTM zones), and their sub grids (100000m, 10000m, 1000m). Each grid or sub-grid is labeled using the standardized MGRS name for the current area.

You can create and add an MGRS grid on any geo-referenced manager view (that is, any view that supports the IlvCoordinateSystemProperty). For example, to add an MGRS grid containing all MGRS zones as a decoration of the view:

IlvMGRSGrid grid = new IlvMGRSGrid();

IlvMGRSGridZone.addAllZones(grid);

view.addViewDecoration(grid);

The IlvLatLonGrid class

The IlvLatLonGrid class displays a set of auto-adaptive grids and labels along latitude or longitude lines on top of a geographic view. If the grid is auto-adaptive, the step between each successive lat/lon line is dependant on the scale of the current view.

You can create and add an MGRS grid on any geo-referenced manager view (that is, any view that supports the IlvCoordinateSystemProperty). For example, to create a lat/lon grid layer:

view.getManager().addLayer(new IlvLatLonGrid()-1);

By default, the IlvLatLonGrid creates only the points at the corners of each grid square. If you are using a coordinate system that transforms the map in a non-linear way (such as Orthographic projection, UTM projection, and so on), you can increase the number of intermediate points on each grid square in order to show a smoother version of the grid:

lgrid.setSmoothness(4);

Writing specific grids

The easiest way to implement your own grid system is to start with an empty MGRS grid and then add your own zones to it. For examples of this, see the Map Builder GridManager class.

Integrating grids into map layers

As the grids are implemented as manager layers, you only need to connect these to an IlvMapLayer.

This map layer must be created, styled and integrated in the map layer tree model:

IlvMapLayerTreeModel ltm =

IlvMapLayerTreeProperty.GetMapLayerTreeModel(view.getManager());

IlvMapLayer mapInsertionLayer = new IlvMapLayer();

mapInsertionLayer.setStyle(new IlvGridStyle());

ltm.addChild(null, mapInsertionLayer);

Then you can integrate the grid manager layer into it:

mapInsertionLayer.insert(grid);

You can also use an IlvDelayedDecoration manager layer to encapsulate the grid. Whenever the user moves or zooms the grid rapidly, a simplified version of the grid is used, which displays more quickly. When the user stops moving or zooming the grid, the full grid is displayed:

IlvDelayedDecoration delayedGrid = new IlvDelayedDecoration(200);

delayedGrid.setDecoration(grid);

mapInsertionLayer.insert(delayedGrid);

The IlvGridStyle class

The IlvGridStyle class is used when displaying grids. It defines the following attributes:

Grid Styling Properties
Property name	Content
GRID_COLOR	The Color used to display grid lines.
TEXT_FONT	The Font of grid labels.
TEXT_COLOR	The Color used to display grid labels.
OUTLINE_COLOR	The Color of the outline of the grid labels.

Map scales and layer styles

As a result of the use of the IlvMapStyleControllerProperty property of the manager (and its underlying IlvMapStyleController), layer styles are dependant on the current scale of the map. Every style attribute of a map layer can be different at different scales.

One of the most widely used attribute changes is the VISIBLE_IN_VIEW attribute, which is used to show and hide different map layers at particular scales. Using the same mechanism, your users can also change colors, line thickness, decorations and so on. Whenever the scale changes, the scale controller can change the current map layer styles, if required. This change of style usually triggers a view repaint, because the attributes of the objects have changed.

Some objects also listen to these style changes in order to re-render themselves. For example, if the color model of a raster style changes, all the images that depend on the style need to be re-created.

You can add dynamic styles with API calls such as:

IlvMapStyleController themeControl=

IlvMapStyleControllerProperty.GetMapStyleController(view.getManager());

themeControl.addTheme(0.001,mapLayer,"new style");

themeControl.getStyle(mapLayer,0.001).setVisibleInView(true);

When you add dynamic styles, be careful to ensure that you still manage style inheritance. When adding a new map layer into a parent layer, you can do this as follows:

IlvMapDynamicStyle []t=themeControl.getThemes(mapLayer);

for (int i = 0; i < t.length; i++) {

t[i].getStyle().setParent(parentLayer.getStyle());

}

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.

Map attribute filters

A IlvMapAttributeFilter object is used to compute the value of a styling attribute from a value found in an IlvGraphic instance. Typically, this value is retrieved from the IlvFeatureAttributeProperty named property attached to a IlvGraphic object. To install such a filter, you set it to an IlvMapStyle object.

The following example shows a custom filter class that defines the foreground of map graphic objects according to their “VALUE” feature attribute.

/**

* Computes the foreground from a graphic's IlvFeatureAttribute

class ColorAttributeFilter implements IlvMapAttributeFilter {

/**

* Method that returns the new color computed from the "VALUE"

* feature attribute. If DEFAULT_VALUE is returned, the style value on which

* the filter is installed will not be affected.

public Object get(IlvGraphic g, String attributeName) {

if(IlvPolylineStyle.FOREGROUND.equals(attributeName)) {

IlvAttributeProperty p = (IlvAttributeProperty)

g.getNamedProperty(IlvAttributeProperty.NAME);

if(p == null)

return DEFAULT_VALUE;

Object o = p.getValue("VALUE");

Object ret = convertObjectToColor(o);

if(ret == null)

return DEFAULT_VALUE;

return ret;

}

The following code example shows how to install a custom filter class in a map layer style.

IlvMapAttributeFilter filter = new ColorAttributeFilter();

IlvMapLayer layer = getLayer();

IlvMapStyle style = layer.getStyle();

style.setAttributeFilter(filter);

Once the filter is installed, each request to retrieve an attribute value is passed to the get method of the filter.