Package org.geotools.mbstyle.function

Class ZoomLevelFunction

Object

ExpressionAbstract

DefaultExpression

FunctionExpressionImpl

ZoomLevelFunction

All Implemented Interfaces:

Expression, Function, FunctionExpression, Factory

public class ZoomLevelFunction
extends FunctionExpressionImpl

Function that takes a scale denominator and a srid and outputs the zoom level.

Note: EPSG:3857 is currently the only supported srid, and zoom levels are assumed to be at the equator.

Example:

 ff.function("zoomLevel",
               ff.function("env", ff.literal("wms_scale_denominator")),
               ff.literal("EPSG:3857")
            );
 

The above function would evaluate to the zoomLevel that corresponds to the current environment's wms_scale_denominator, for EPSG:3857.

Example 2:

 ff.function("zoomLevel",
               ff.literal(136494.693347),
               ff.literal("EPSG:3857")
            );
 

The above function would evaluate to a zoomLevel of 12.

Field Summary

Fields

Modifier and Type	Field	Description
static final double	EPSG_3857_O_SCALE	Scale denominator of the root tile.
static final String	MBSTYLE_ROOT_TILE_PIXELS_KEY	Name of the system variable controlling ROOT_TILE_PIXELS
static final FunctionName	NAME
static final int	ROOT_TILE_PIXELS	Number of pixels in the side of the root tile.

Fields inherited from class FunctionExpressionImpl

fallback, functionName, name, params

Fields inherited from interface Expression

NIL

Constructor Summary

Constructors

Constructor	Description
ZoomLevelFunction()

Method Summary

Modifier and Type	Method	Description
Object	evaluate(Object feature)	Subclass should override, default implementation returns null.
int	getArgCount()

Methods inherited from class FunctionExpressionImpl

accept, equals, functionName, getExpression, getFallbackValue, getFunctionName, getImplementationHints, getName, getParameters, hashCode, setFallbackValue, setParameters, toString

Methods inherited from class DefaultExpression

isAttributeExpression, isExpression, isFunctionExpression, isGeometryExpression, isLiteralExpression, isMathExpression

Methods inherited from class ExpressionAbstract

evaluate

Methods inherited from class Object

clone, finalize, getClass, notify, notifyAll, wait, wait, wait

Methods inherited from interface Expression

evaluate

Field Details

NAME

public static final FunctionName NAME

MBSTYLE_ROOT_TILE_PIXELS_KEY

public static final String MBSTYLE_ROOT_TILE_PIXELS_KEY

Name of the system variable controlling ROOT_TILE_PIXELS

See Also:

• Constant Field Values

ROOT_TILE_PIXELS

public static final int ROOT_TILE_PIXELS

Number of pixels in the side of the root tile. Assumes 512 if not otherwise configured.

EPSG_3857_O_SCALE

public static final double EPSG_3857_O_SCALE

Scale denominator of the root tile. Changes based on the ROOT_TILE_PIXELS value.

Constructor Details

ZoomLevelFunction

public ZoomLevelFunction()

Method Details

getArgCount

public int getArgCount()

evaluate

public Object evaluate(Object feature)

Description copied from class: ExpressionAbstract

Subclass should override, default implementation returns null.

Specified by:

evaluate in interface Expression

Overrides:

evaluate in class FunctionExpressionImpl

Returns:

default implementation returns null