javax.media.jai
Class BorderExtender

java.lang.Object
  |
  +--javax.media.jai.BorderExtender

All Implemented Interfaces:

Serializable

Direct Known Subclasses:

BorderExtenderConstant, BorderExtenderCopy, BorderExtenderReflect, BorderExtenderWrap, BorderExtenderZero

public abstract class BorderExtender

extends Object

implements Serializable

An abstract superclass for classes that extend or "pad" a WritableRaster with additional pixel data taken from a PlanarImage. Instances of BorderExtender are used by the getExtendedData() and copyExtendedData() methods in PlanarImage.

Each instance of BorderExtender has an extend() method that takes a WritableRaster and a PlanarImage. The portion of the raster that intersects the bounds of the image will already contain a copy of the image data. The remaining area is to be filled in according to the policy of the BorderExtender subclass.

The standard subclasses of BorderExtender are BorderExtenderZero, which fills pixels with zeros; BorderExtenderConstant, which fills pixels with a given constant value; BorderExtenderCopy, which copies the edge pixels of the image; BorderExtenderWrap, which tiles the plane with repeating copies of the image; and BorderExtenderReflect, which is like BorderExtenderWrap except that each copy of the image is suitably reflected.

Instances of BorderExtenderConstant are constructed in the usual way. Instances of the other standard subclasses are obtained by means of the createInstance() method of this class.

BorderExtenderCopy is particularly useful as a way of padding image data prior to performing area or geometric operations such as convolution, scaling, and rotation.

See Also:

PlanarImage.getExtendedData(java.awt.Rectangle, javax.media.jai.BorderExtender), PlanarImage.copyExtendedData(java.awt.image.WritableRaster, javax.media.jai.BorderExtender), BorderExtenderConstant, BorderExtenderCopy, BorderExtenderReflect, BorderExtenderWrap, BorderExtenderZero, Serialized Form

Field Summary

static int	BORDER_COPY A constant for use in the createInstance method.
static int	BORDER_REFLECT A constant for use in the createInstance method.
static int	BORDER_WRAP A constant for use in the createInstance method.
static int	BORDER_ZERO A constant for use in the createInstance method.

Constructor Summary

BorderExtender()

Method Summary

static BorderExtender	createInstance(int extenderType) Returns an instance of BorderExtender that implements a given extension policy.
abstract void	extend(WritableRaster raster, PlanarImage im) Fills in the portions of a given WritableRaster that lie outside the bounds of a given PlanarImage.

Methods inherited from class java.lang.Object

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

Field Detail

BORDER_ZERO

public static final int BORDER_ZERO

A constant for use in the createInstance method.

BORDER_COPY

public static final int BORDER_COPY

A constant for use in the createInstance method.

BORDER_REFLECT

public static final int BORDER_REFLECT

A constant for use in the createInstance method.

BORDER_WRAP

public static final int BORDER_WRAP

A constant for use in the createInstance method.

Constructor Detail

BorderExtender

public BorderExtender()

Method Detail

extend

public abstract void extend(WritableRaster raster,
                            PlanarImage im)

Fills in the portions of a given WritableRaster that lie outside the bounds of a given PlanarImage. Depending on the policy of the BorderExtender, data might or might not be derived from the PlanarImage.

The portion of raster that lies within im.getBounds() must not be altered. The pixels within this region should not be assumed to have any particular values.

Each subclass may implement a different policy regarding how the extension data is computed.

Parameters:

raster - The WritableRaster the border area of which is to be filled according to the policy of the BorderExtender.

im - The PlanarImage which may provide the data with which to fill the border area of the WritableRaster.

Throws:

IllegalArgumentException - if either parameter is null.

createInstance

public static BorderExtender createInstance(int extenderType)

Returns an instance of BorderExtender that implements a given extension policy. The policies understood by this method are:

BORDER_ZERO: set sample values to zero.

BORDER_COPY: set sample values to copies of the nearest valid pixel. For example, pixels to the left of the valid rectangle will take on the value of the valid edge pixel in the same row. Pixels both above and to the left of the valid rectangle will take on the value of the upper-left pixel.

BORDER_REFLECT: the output image is defined as if mirrors were placed along the edges of the source image. Thus if the left edge of the valid rectangle lies at X = 10, pixel (9, Y) will be a copy of pixel (10, Y); pixel (6, Y) will be a copy of pixel (13, Y).

BORDER_WRAP: the source image is tiled repeatedly in the plane.

Note that this method may not be used to create an instance of BorderExtenderConstant.

Any other input value will cause an IllegalArgumentException to be thrown.

Parameters:

extenderType - The type of BorderExtender to create. Must be one of the predefined class constants BORDER_COPY, BORDER_REFLECT, BORDER_WRAP, or BORDER_ZERO.

Throws:

IllegalArgumentException - if the supplied parameter is not one of the supported predefined constants.