java.awt
Class Image

java.lang.Object
  java.awt.Image

Direct Known Subclasses:

BufferedImage, VolatileImage

public abstract class Image

extends Object

The abstract class Image is the superclass of all classes that represent graphical images. The image must be obtained in a platform-specific manner.

Since:

JDK1.0

Author:

Sami Shaio, Arthur van Hoff

Field Summary

static int	SCALE_AREA_AVERAGING Use the Area Averaging image scaling algorithm.
static int	SCALE_DEFAULT Use the default image-scaling algorithm.
static int	SCALE_FAST Choose an image-scaling algorithm that gives higher priority to scaling speed than smoothness of the scaled image.
static int	SCALE_REPLICATE Use the image scaling algorithm embodied in the ReplicateScaleFilter class.
static int	SCALE_SMOOTH Choose an image-scaling algorithm that gives higher priority to image smoothness than scaling speed.
static Object	UndefinedProperty The UndefinedProperty object should be returned whenever a property which was not defined for a particular image is fetched.

Constructor Summary

Image()

Method Summary

abstract void	flush() Flushes all resources being used by this Image object.
abstract Graphics	getGraphics() Creates a graphics context for drawing to an off-screen image.
abstract int	getHeight(ImageObserver observer) Determines the height of the image.
abstract Object	getProperty(String name, ImageObserver observer) Gets a property of this image by name.
Image	getScaledInstance(int width, int height, int hints) Creates a scaled version of this image.
abstract ImageProducer	getSource() Gets the object that produces the pixels for the image.
abstract int	getWidth(ImageObserver observer) Determines the width of the image.

Methods inherited from class java.lang.Object

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

Field Detail

UndefinedProperty

public static final Object UndefinedProperty

The UndefinedProperty object should be returned whenever a property which was not defined for a particular image is fetched.

SCALE_DEFAULT

public static final int SCALE_DEFAULT

Use the default image-scaling algorithm.

Since:

JDK1.1

See Also:

Constant Field Values

SCALE_FAST

public static final int SCALE_FAST

Choose an image-scaling algorithm that gives higher priority to scaling speed than smoothness of the scaled image.

Since:

JDK1.1

See Also:

Constant Field Values

SCALE_SMOOTH

public static final int SCALE_SMOOTH

Choose an image-scaling algorithm that gives higher priority to image smoothness than scaling speed.

Since:

JDK1.1

See Also:

Constant Field Values

SCALE_REPLICATE

public static final int SCALE_REPLICATE

Use the image scaling algorithm embodied in the ReplicateScaleFilter class. The Image object is free to substitute a different filter that performs the same algorithm yet integrates more efficiently into the imaging infrastructure supplied by the toolkit.

Since:

JDK1.1

See Also:

ReplicateScaleFilter, Constant Field Values

SCALE_AREA_AVERAGING

public static final int SCALE_AREA_AVERAGING

Use the Area Averaging image scaling algorithm. The image object is free to substitute a different filter that performs the same algorithm yet integrates more efficiently into the image infrastructure supplied by the toolkit.

Since:

JDK1.1

See Also:

AreaAveragingScaleFilter, Constant Field Values

Constructor Detail

Image

public Image()

Method Detail

getWidth

public abstract int getWidth(ImageObserver observer)

Determines the width of the image. If the width is not yet known, this method returns -1 and the specified ImageObserver object is notified later.

Parameters:

observer - an object waiting for the image to be loaded.

Returns:

the width of this image, or -1 if the width is not yet known.

See Also:

getHeight(java.awt.image.ImageObserver), ImageObserver

getHeight

public abstract int getHeight(ImageObserver observer)

Determines the height of the image. If the height is not yet known, this method returns -1 and the specified ImageObserver object is notified later.

Parameters:

observer - an object waiting for the image to be loaded.

Returns:

the height of this image, or -1 if the height is not yet known.

See Also:

getWidth(java.awt.image.ImageObserver), ImageObserver

getSource

public abstract ImageProducer getSource()

Gets the object that produces the pixels for the image. This method is called by the image filtering classes and by methods that perform image conversion and scaling.

Returns:

the image producer that produces the pixels for this image.

See Also:

ImageProducer

getGraphics

public abstract Graphics getGraphics()

Creates a graphics context for drawing to an off-screen image. This method can only be called for off-screen images.

Returns:

a graphics context to draw to the off-screen image.

See Also:

Graphics, Component.createImage(int, int)

getProperty

public abstract Object getProperty(String name,
                                   ImageObserver observer)

Gets a property of this image by name.

Individual property names are defined by the various image formats. If a property is not defined for a particular image, this method returns the UndefinedProperty object.

If the properties for this image are not yet known, this method returns null, and the ImageObserver object is notified later.

The property name "comment" should be used to store an optional comment which can be presented to the application as a description of the image, its source, or its author.

Parameters:

name - a property name.

observer - an object waiting for this image to be loaded.

Returns:

the value of the named property.

See Also:

ImageObserver, UndefinedProperty

getScaledInstance

public Image getScaledInstance(int width,
                               int height,
                               int hints)

Creates a scaled version of this image. A new Image object is returned which will render the image at the specified width and height by default. The new Image object may be loaded asynchronously even if the original source image has already been loaded completely. If either the width or height is a negative number then a value is substituted to maintain the aspect ratio of the original image dimensions.

Parameters:

width - the width to which to scale the image.

height - the height to which to scale the image.

hints - flags to indicate the type of algorithm to use for image resampling.

Returns:

a scaled version of the image.

Since:

JDK1.1

See Also:

SCALE_DEFAULT, SCALE_FAST, SCALE_SMOOTH, SCALE_REPLICATE, SCALE_AREA_AVERAGING

flush

public abstract void flush()

Flushes all resources being used by this Image object. This includes any pixel data that is being cached for rendering to the screen as well as any system resources that are being used to store data or pixels for the image. The image is reset to a state similar to when it was first created so that if it is again rendered, the image data will have to be recreated or fetched again from its source.

This method always leaves the image in a state such that it can be reconstructed. This means the method applies only to cached or other secondary representations of images such as those that have been generated from an ImageProducer (read from a file, for example). It does nothing for off-screen images that have only one copy of their data.