org.apache.sis.geometry

Class Envelopes

Object

Static

Envelopes

public final class Envelopes
extends Static

Transforms envelopes to new Coordinate Reference Systems, and miscellaneous utilities.

Envelope transformations

All transform(…) methods in this class take in account the curvature of the transformed shape. For example the shape of a geographic envelope (figure below on the left side) is not rectangular in a conic projection (figure below on the right side). In order to get the envelope represented by the red rectangle, projecting the four corners of the geographic envelope is not sufficient since we would miss the southerner part.

Example of curvature induced by a map projection

Envelope before map projection	Shape of the projected envelope

Apache SIS tries to detect the curvature by transforming intermediate points in addition to the corners. While optional, it is strongly recommended that all Math­Transform implementations involved in the operation (directly or indirectly) support derivative, for more accurate calculation of curve extremum. This is the case of most Apache SIS implementations.

The transform(…) methods in this class expect an arbitrary Envelope with one of the following arguments: Math­Transform, Coordinate­Operation or Coordinate­Reference­System. The recommended method is the one expecting a Coordinate­Operation object, since it contains sufficient information for handling the cases of envelopes that encompass a pole. The method expecting a Coordinate­Reference­System object is merely a convenience method that infers the coordinate operation itself, but at the cost of performance if the same operation needs to be applied on many envelopes.

Since:

0.3

See Also:

Extents, CRS

Defined in the sis-referencing module

Method Summary

Modifier and Type	Method and Description
static Envelope	fromWKT(CharSequence wkt) Returns the bounding box of a geometry defined in Well Known Text (WKT) format.
static String	toPolygonWKT(Envelope envelope) Formats the given envelope as a POLYGON element in the Well Known Text (WKT) format.
static String	toString(Envelope envelope) Formats the given envelope as a BOX element.
static GeneralEnvelope	transform(CoordinateOperation operation, Envelope envelope) Transforms an envelope using the given coordinate operation.
static Envelope	transform(Envelope envelope, CoordinateReferenceSystem targetCRS) Transforms the given envelope to the specified CRS.
static GeneralEnvelope	transform(MathTransform transform, Envelope envelope) Transforms an envelope using the given math transform.

Methods inherited from class Object

clone, equals, finalize, get­Class, hash­Code, notify, notify­All, to­String, wait, wait, wait

Method Detail

transform

public static Envelope transform(Envelope envelope,
                                 CoordinateReferenceSystem targetCRS)
                          throws TransformException

Transforms the given envelope to the specified CRS. If any argument is null, or if the envelope CRS is null or the same instance than the given target CRS, then the given envelope is returned unchanged. Otherwise a new transformed envelope is returned.

Performance tip

If there is many envelopes to transform with the same source and target CRS, then it is more efficient to get the Coordinate­Operation or Math­Transform instance once and invoke one of the others transform(…) methods.

Parameters:

envelope - the envelope to transform (may be null).

target­CRS - the target CRS (may be null).

Returns:

a new transformed envelope, or directly envelope if no change was required.

Throws:

Transform­Exception - if a transformation was required and failed.

Since:

0.5

transform

public static GeneralEnvelope transform(MathTransform transform,
                                        Envelope envelope)
                                 throws TransformException

Transforms an envelope using the given math transform. The transformation is only approximative: the returned envelope may be bigger than necessary, or smaller than required if the bounding box contains a pole.

Limitation

This method can not handle the case where the envelope contains the North or South pole, or when it crosses the ±180° longitude, because Math­Transform does not carry sufficient information. For a more robust envelope transformation, use transform(Coordinate­Operation, Envelope) instead.

Parameters:

transform - the transform to use.

envelope - envelope to transform, or null. This envelope will not be modified.

Returns:

the transformed envelope, or null if envelope was null.

Throws:

Transform­Exception - if a transform failed.

Since:

0.5

See Also:

transform(Coordinate­Operation, Envelope)

transform

public static GeneralEnvelope transform(CoordinateOperation operation,
                                        Envelope envelope)
                                 throws TransformException

Transforms an envelope using the given coordinate operation. The transformation is only approximative: the returned envelope may be bigger than the smallest possible bounding box, but should not be smaller in most cases.

This method can handle the case where the envelope contains the North or South pole, or when it cross the ±180° longitude.

Note: If the envelope CRS is non-null, then the caller should ensure that the operation source CRS is the same than the envelope CRS. In case of mismatch, this method transforms the envelope to the operation source CRS before to apply the operation. This extra step may cause a lost of accuracy. In order to prevent this method from performing such pre-transformation (if not desired), callers can ensure that the envelope CRS is null before to call this method.

Parameters:

operation - the operation to use.

envelope - envelope to transform, or null. This envelope will not be modified.

Returns:

the transformed envelope, or null if envelope was null.

Throws:

Transform­Exception - if a transform failed.

Since:

0.5

See Also:

transform(Math­Transform, Envelope)

fromWKT

public static Envelope fromWKT(CharSequence wkt)
                        throws FactoryException

Returns the bounding box of a geometry defined in Well Known Text (WKT) format. This method does not check the consistency of the provided WKT. For example it does not check that every points in a LINESTRING have the same dimension. However this method ensures that the parenthesis are balanced, in order to catch some malformed WKT.

Example:

• BOX(-180 -90, 180 90) (not really a geometry, but understood by many software products)
• POINT(6 10)
• MULTIPOLYGON(((1 1, 5 1, 1 5, 1 1),(2 2, 3 2, 3 3, 2 2)))
• GEOMETRYCOLLECTION(POINT(4 6),LINESTRING(3 8,7 10))

See General­Envelope.General­Envelope(Char­Sequence) for more information about the parsing rules.

Parameters:

wkt - the BOX, POLYGON or other kind of element to parse.

Returns:

the envelope of the given geometry.

Throws:

Factory­Exception - if the given WKT can not be parsed.

See Also:

to­String(Envelope), CRS.from­WKT(String), org.apache.sis.io.wkt

toString

public static String toString(Envelope envelope)

Formats the given envelope as a BOX element. The output is like below, where n is the number of dimensions (omitted if equals to 2):

BOXnD(lower corner, upper corner)

Note: The BOX element is not part of the standard Well Known Text (WKT) format. However it is understood by many software libraries, for example GDAL and PostGIS.

The string returned by this method can be parsed by the General­Envelope constructor.

Parameters:

envelope - the envelope to format.

Returns:

this envelope as a BOX or BOX3D (most typical dimensions) element.

See Also:

from­WKT(Char­Sequence), org.apache.sis.io.wkt

toPolygonWKT

public static String toPolygonWKT(Envelope envelope)
                           throws IllegalArgumentException

Formats the given envelope as a POLYGON element in the Well Known Text (WKT) format. POLYGON can be used as an alternative to BOX when the element needs to be considered as a standard WKT geometry.

The string returned by this method can be parsed by the General­Envelope constructor.

Parameters:

envelope - the envelope to format.

Returns:

the envelope as a POLYGON in WKT format.

Throws:

Illegal­Argument­Exception - if the given envelope can not be formatted.

See Also:

org.apache.sis.io.wkt