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JavaTM 2 Platform Std. Ed. v1.5.0

java.awt
Class Image

java.lang.Object
  java.awt.Image

Direct Known Subclasses:: BufferedImage, VolatileImage

public abstract class Image
extends Object
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

Field Summary

protected float accelerationPriority
          Priority for accelerating this image.

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.

float getAccelerationPriority()
          Returns the current value of the acceleration priority hint.

ImageCapabilities getCapabilities(GraphicsConfiguration gc)
          Returns an ImageCapabilities object which can be inquired as to the capabilities of this Image on the specified GraphicsConfiguration.

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.

void setAccelerationPriority(float priority)
          Sets a hint for this image about how important acceleration is.

Methods inherited from class java.lang.Object

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

Field Detail

accelerationPriority

protected float accelerationPriority

Priority for accelerating this image. Subclasses are free to set different default priorities and applications are free to set the priority for specific images via the setAccelerationPriority(float) method.

Since:: 1.5

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.
Throws:: UnsupportedOperationException - if called for a non-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.
Throws:: NullPointerException - if the property name is null.
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 width 
 or height is a negative number then a value is 
 substituted to maintain the aspect ratio of the original image 
 dimensions. If both width and height
 are negative, then the original image dimensions are used.


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.
Throws:
IllegalArgumentException - if width
             or height is zero.
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.








getCapabilities
public ImageCapabilities getCapabilities(GraphicsConfiguration gc)

Returns an ImageCapabilities object which can be
 inquired as to the capabilities of this
 Image on the specified GraphicsConfiguration.
 This allows programmers to find
 out more runtime information on the specific Image
 object that they have created.  For example, the user
 might create a BufferedImage but the system may have
 no video memory left for creating an image of that
 size on the given GraphicsConfiguration, so although the object
 may be acceleratable in general, it is
 does not have that capability on this GraphicsConfiguration.


Parameters:
gc - a GraphicsConfiguration object.  A value of null
 for this parameter will result in getting the image capabilities
 for the default GraphicsConfiguration.
Returns:
an ImageCapabilities object that contains
 the capabilities of this Image on the specified
 GraphicsConfiguration.
Since:
  1.5
See Also:
VolatileImage.getCapabilities()





setAccelerationPriority
public void setAccelerationPriority(float priority)

Sets a hint for this image about how important acceleration is.
 This priority hint is used to compare to the priorities of other
 Image objects when determining how to use scarce acceleration
 resources such as video memory.  When and if it is possible to
 accelerate this Image, if there are not enough resources available
 to provide that acceleration but enough can be freed up by
 de-acceleration some other image of lower priority, then that other
 Image may be de-accelerated in deference to this one.  Images
 that have the same priority take up resources on a first-come,
 first-served basis.


Parameters:
priority - a value between 0 and 1, inclusive, where higher
 values indicate more importance for acceleration.  A value of 0
 means that this Image should never be accelerated.  Other values
 are used simply to determine acceleration priority relative to other
 Images.
Throws:
IllegalArgumentException - if priority is less
 than zero or greater than 1.
Since:
  1.5






getAccelerationPriority
public float getAccelerationPriority()

Returns the current value of the acceleration priority hint.



Returns:
value between 0 and 1, inclusive, which represents the current
 priority value
Since:
  1.5
See Also:
setAccelerationPriority







Copyright 2003 Sun Microsystems, Inc. All rights reserved

java.awt Class Image