JDK8/Java8源码在线阅读
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package java.awt;
import java.awt.image.ImageProducer;
import java.awt.image.ImageObserver;
import java.awt.image.ImageFilter;
import java.awt.image.FilteredImageSource;
import java.awt.image.AreaAveragingScaleFilter;
import java.awt.image.ReplicateScaleFilter;
import sun.awt.image.SurfaceManager;
/**
* The abstract class <code>Image</code> is the superclass of all
* classes that represent graphical images. The image must be
* obtained in a platform-specific manner.
*
* @author Sami Shaio
* @author Arthur van Hoff
* @since JDK1.0
*/
public abstract class Image {
/**
* convenience object; we can use this single static object for
* all images that do not create their own image caps; it holds the
* default (unaccelerated) properties.
*/
private static ImageCapabilities defaultImageCaps =
new ImageCapabilities(false);
/**
* 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
* <code>setAccelerationPriority(float)</code> method.
* @since 1.5
*/
protected float accelerationPriority = .5f;
/**
* Determines the width of the image. If the width is not yet known,
* this method returns <code>-1</code> and the specified
* <code>ImageObserver</code> object is notified later.
* @param observer an object waiting for the image to be loaded.
* @return the width of this image, or <code>-1</code>
* if the width is not yet known.
* @see java.awt.Image#getHeight
* @see java.awt.image.ImageObserver
*/
public abstract int getWidth(ImageObserver observer);
/**
* Determines the height of the image. If the height is not yet known,
* this method returns <code>-1</code> and the specified
* <code>ImageObserver</code> object is notified later.
* @param observer an object waiting for the image to be loaded.
* @return the height of this image, or <code>-1</code>
* if the height is not yet known.
* @see java.awt.Image#getWidth
* @see java.awt.image.ImageObserver
*/
public abstract int getHeight(ImageObserver observer);
/**
* 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.
* @return the image producer that produces the pixels
* for this image.
* @see java.awt.image.ImageProducer
*/
public abstract ImageProducer getSource();
/**
* Creates a graphics context for drawing to an off-screen image.
* This method can only be called for off-screen images.
* @return a graphics context to draw to the off-screen image.
* @exception UnsupportedOperationException if called for a
* non-off-screen image.
* @see java.awt.Graphics
* @see java.awt.Component#createImage(int, int)
*/
public abstract Graphics getGraphics();
/**
* Gets a property of this image by name.
* <p>
* Individual property names are defined by the various image
* formats. If a property is not defined for a particular image, this
* method returns the <code>UndefinedProperty</code> object.
* <p>
* If the properties for this image are not yet known, this method
* returns <code>null</code>, and the <code>ImageObserver</code>
* object is notified later.
* <p>
* The property name <code>"comment"</code> 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.
* @param name a property name.
* @param observer an object waiting for this image to be loaded.
* @return the value of the named property.
* @throws NullPointerException if the property name is null.
* @see java.awt.image.ImageObserver
* @see java.awt.Image#UndefinedProperty
*/
public abstract Object getProperty(String name, ImageObserver observer);
/**
* The <code>UndefinedProperty</code> object should be returned whenever a
* property which was not defined for a particular image is fetched.
*/
public static final Object UndefinedProperty = new Object();
/**
* Creates a scaled version of this image.
* A new <code>Image</code> object is returned which will render
* the image at the specified <code>width</code> and
* <code>height</code> by default. The new <code>Image</code> object
* may be loaded asynchronously even if the original source image
* has already been loaded completely.
*
* <p>
*
* If either <code>width</code>
* or <code>height</code> is a negative number then a value is
* substituted to maintain the aspect ratio of the original image
* dimensions. If both <code>width</code> and <code>height</code>
* are negative, then the original image dimensions are used.
*
* @param width the width to which to scale the image.
* @param height the height to which to scale the image.
* @param hints flags to indicate the type of algorithm to use
* for image resampling.
* @return a scaled version of the image.
* @exception IllegalArgumentException if <code>width</code>
* or <code>height</code> is zero.
* @see java.awt.Image#SCALE_DEFAULT
* @see java.awt.Image#SCALE_FAST
* @see java.awt.Image#SCALE_SMOOTH
* @see java.awt.Image#SCALE_REPLICATE
* @see java.awt.Image#SCALE_AREA_AVERAGING
* @since JDK1.1
*/
public Image getScaledInstance(int width, int height, int hints) {
ImageFilter filter;
if ((hints & (SCALE_SMOOTH | SCALE_AREA_AVERAGING)) != 0) {
filter = new AreaAveragingScaleFilter(width, height);
} else {
filter = new ReplicateScaleFilter(width, height);
}
ImageProducer prod;
prod = new FilteredImageSource(getSource(), filter);
return Toolkit.getDefaultToolkit().createImage(prod);
}
/**
* Use the default image-scaling algorithm.
* @since JDK1.1
*/
public static final int SCALE_DEFAULT = 1;
/**
* Choose an image-scaling algorithm that gives higher priority
* to scaling speed than smoothness of the scaled image.
* @since JDK1.1
*/
public static final int SCALE_FAST = 2;
/**
* Choose an image-scaling algorithm that gives higher priority
* to image smoothness than scaling speed.
* @since JDK1.1
*/
public static final int SCALE_SMOOTH = 4;
/**
* Use the image scaling algorithm embodied in the
* <code>ReplicateScaleFilter</code> class.
* The <code>Image</code> 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.
* @see java.awt.image.ReplicateScaleFilter
* @since JDK1.1
*/
public static final int SCALE_REPLICATE = 8;
/**
* 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.
* @see java.awt.image.AreaAveragingScaleFilter
* @since JDK1.1
*/
public static final int SCALE_AREA_AVERAGING = 16;
/**
* Flushes all reconstructable 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 if they can be recreated.
* 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.
* <p>
* Examples of how this method affects specific types of Image object:
* <ul>
* <li>
* BufferedImage objects leave the primary Raster which stores their
* pixels untouched, but flush any information cached about those
* pixels such as copies uploaded to the display hardware for
* accelerated blits.
* <li>
* Image objects created by the Component methods which take a
* width and height leave their primary buffer of pixels untouched,
* but have all cached information released much like is done for
* BufferedImage objects.
* <li>
* VolatileImage objects release all of their pixel resources
* including their primary copy which is typically stored on
* the display hardware where resources are scarce.
* These objects can later be restored using their
* {@link java.awt.image.VolatileImage#validate validate}
* method.
* <li>
* Image objects created by the Toolkit and Component classes which are
* loaded from files, URLs or produced by an {@link ImageProducer}
* are unloaded and all local resources are released.
* These objects can later be reloaded from their original source
* as needed when they are rendered, just as when they were first
* created.
* </ul>
*/
public void flush() {
if (surfaceManager != null) {
surfaceManager.flush();
}
}
/**
* 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
* does not have that capability on this GraphicsConfiguration.
* @param gc a <code>GraphicsConfiguration</code> object. A value of null
* for this parameter will result in getting the image capabilities
* for the default <code>GraphicsConfiguration</code>.
* @return an <code>ImageCapabilities</code> object that contains
* the capabilities of this <code>Image</code> on the specified
* GraphicsConfiguration.
* @see java.awt.image.VolatileImage#getCapabilities()
* VolatileImage.getCapabilities()
* @since 1.5
*/
public ImageCapabilities getCapabilities(GraphicsConfiguration gc) {
if (surfaceManager != null) {
return surfaceManager.getCapabilities(gc);
}
// Note: this is just a default object that gets returned in the
// absence of any more specific information from a surfaceManager.
// Subclasses of Image should either override this method or
// make sure that they always have a non-null SurfaceManager
// to return an ImageCapabilities object that is appropriate
// for their given subclass type.
return defaultImageCaps;
}
/**
* 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-accelerating 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.
* @param priority a value between 0 and 1, inclusive, where higher
* values indicate more importance for acceleration. A value of 0
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