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package java.awt.image;

import java.awt.Image;



An asynchronous update interface for receiving notifications about
Image information as the Image is constructed.

Author:     Jim Graham
/**
 * An asynchronous update interface for receiving notifications about
 * Image information as the Image is constructed.
 *
 * @author      Jim Graham
 */
public interface ImageObserver {
    
This method is called when information about an image which was
previously requested using an asynchronous interface becomes
available.  Asynchronous interfaces are method calls such as
getWidth(ImageObserver) and drawImage(img, x, y, ImageObserver)
which take an ImageObserver object as an argument.  Those methods
register the caller as interested either in information about
the overall image itself (in the case of getWidth(ImageObserver))
or about an output version of an image (in the case of the
drawImage(img, x, y, [w, h,] ImageObserver) call).

This method
should return true if further updates are needed or false if the
required information has been acquired.  The image which was being
tracked is passed in using the img argument.  Various constants
are combined to form the infoflags argument which indicates what
information about the image is now available.  The interpretation
of the x, y, width, and height arguments depends on the contents
of the infoflags argument.

 The infoflags argument should be the bitwise inclusive OR of the following flags: WIDTH, HEIGHT, PROPERTIES, SOMEBITS, FRAMEBITS, ALLBITS, ERROR, ABORT. 
Params:
  • img –   the image being observed.
  • infoflags –  the bitwise inclusive OR of the following flags: WIDTH, HEIGHT, PROPERTIES, SOMEBITS, FRAMEBITS, ALLBITS, ERROR, ABORT.
  • x –   the x coordinate.
  • y –   the y coordinate.
  • width –    the width.
  • height –   the height.
See Also:
Returns: false if the infoflags indicate that the image is completely loaded; true otherwise.
/**
     * This method is called when information about an image which was
     * previously requested using an asynchronous interface becomes
     * available.  Asynchronous interfaces are method calls such as
     * getWidth(ImageObserver) and drawImage(img, x, y, ImageObserver)
     * which take an ImageObserver object as an argument.  Those methods
     * register the caller as interested either in information about
     * the overall image itself (in the case of getWidth(ImageObserver))
     * or about an output version of an image (in the case of the
     * drawImage(img, x, y, [w, h,] ImageObserver) call).
     *
     * <p>This method
     * should return true if further updates are needed or false if the
     * required information has been acquired.  The image which was being
     * tracked is passed in using the img argument.  Various constants
     * are combined to form the infoflags argument which indicates what
     * information about the image is now available.  The interpretation
     * of the x, y, width, and height arguments depends on the contents
     * of the infoflags argument.
     * <p>
     * The {@code infoflags} argument should be the bitwise inclusive
     * <b>OR</b> of the following flags: {@code WIDTH},
     * {@code HEIGHT}, {@code PROPERTIES}, {@code SOMEBITS},
     * {@code FRAMEBITS}, {@code ALLBITS}, {@code ERROR},
     * {@code ABORT}.
     *
     * @param     img   the image being observed.
     * @param     infoflags   the bitwise inclusive OR of the following
     *               flags:  {@code WIDTH}, {@code HEIGHT},
     *               {@code PROPERTIES}, {@code SOMEBITS},
     *               {@code FRAMEBITS}, {@code ALLBITS},
     *               {@code ERROR}, {@code ABORT}.
     * @param     x   the <i>x</i> coordinate.
     * @param     y   the <i>y</i> coordinate.
     * @param     width    the width.
     * @param     height   the height.
     * @return    {@code false} if the infoflags indicate that the
     *            image is completely loaded; {@code true} otherwise.
     *
     * @see #WIDTH
     * @see #HEIGHT
     * @see #PROPERTIES
     * @see #SOMEBITS
     * @see #FRAMEBITS
     * @see #ALLBITS
     * @see #ERROR
     * @see #ABORT
     * @see Image#getWidth
     * @see Image#getHeight
     * @see java.awt.Graphics#drawImage
     */
    public boolean imageUpdate(Image img, int infoflags,
                               int x, int y, int width, int height);

    
This flag in the infoflags argument to imageUpdate indicates that
the width of the base image is now available and can be taken
from the width argument to the imageUpdate callback method.

See Also:
/**
     * This flag in the infoflags argument to imageUpdate indicates that
     * the width of the base image is now available and can be taken
     * from the width argument to the imageUpdate callback method.
     * @see Image#getWidth
     * @see #imageUpdate
     */
    public static final int WIDTH = 1;

    
This flag in the infoflags argument to imageUpdate indicates that
the height of the base image is now available and can be taken
from the height argument to the imageUpdate callback method.

See Also:
/**
     * This flag in the infoflags argument to imageUpdate indicates that
     * the height of the base image is now available and can be taken
     * from the height argument to the imageUpdate callback method.
     * @see Image#getHeight
     * @see #imageUpdate
     */
    public static final int HEIGHT = 2;

    
This flag in the infoflags argument to imageUpdate indicates that
the properties of the image are now available.

See Also:
/**
     * This flag in the infoflags argument to imageUpdate indicates that
     * the properties of the image are now available.
     * @see Image#getProperty
     * @see #imageUpdate
     */
    public static final int PROPERTIES = 4;

    
This flag in the infoflags argument to imageUpdate indicates that
more pixels needed for drawing a scaled variation of the image
are available.  The bounding box of the new pixels can be taken
from the x, y, width, and height arguments to the imageUpdate
callback method.

See Also:
/**
     * This flag in the infoflags argument to imageUpdate indicates that
     * more pixels needed for drawing a scaled variation of the image
     * are available.  The bounding box of the new pixels can be taken
     * from the x, y, width, and height arguments to the imageUpdate
     * callback method.
     * @see java.awt.Graphics#drawImage
     * @see #imageUpdate
     */
    public static final int SOMEBITS = 8;

    
This flag in the infoflags argument to imageUpdate indicates that
another complete frame of a multi-frame image which was previously
drawn is now available to be drawn again.  The x, y, width, and height
arguments to the imageUpdate callback method should be ignored.

See Also:
/**
     * This flag in the infoflags argument to imageUpdate indicates that
     * another complete frame of a multi-frame image which was previously
     * drawn is now available to be drawn again.  The x, y, width, and height
     * arguments to the imageUpdate callback method should be ignored.
     * @see java.awt.Graphics#drawImage
     * @see #imageUpdate
     */
    public static final int FRAMEBITS = 16;

    
This flag in the infoflags argument to imageUpdate indicates that
a static image which was previously drawn is now complete and can
be drawn again in its final form.  The x, y, width, and height
arguments to the imageUpdate callback method should be ignored.

See Also:
/**
     * This flag in the infoflags argument to imageUpdate indicates that
     * a static image which was previously drawn is now complete and can
     * be drawn again in its final form.  The x, y, width, and height
     * arguments to the imageUpdate callback method should be ignored.
     * @see java.awt.Graphics#drawImage
     * @see #imageUpdate
     */
    public static final int ALLBITS = 32;

    
This flag in the infoflags argument to imageUpdate indicates that
an image which was being tracked asynchronously has encountered
an error.  No further information will become available and
drawing the image will fail.
As a convenience, the ABORT flag will be indicated at the same
time to indicate that the image production was aborted.

See Also:
  • imageUpdate
/**
     * This flag in the infoflags argument to imageUpdate indicates that
     * an image which was being tracked asynchronously has encountered
     * an error.  No further information will become available and
     * drawing the image will fail.
     * As a convenience, the ABORT flag will be indicated at the same
     * time to indicate that the image production was aborted.
     * @see #imageUpdate
     */
    public static final int ERROR = 64;

    
This flag in the infoflags argument to imageUpdate indicates that
an image which was being tracked asynchronously was aborted before
production was complete.  No more information will become available
without further action to trigger another image production sequence.
If the ERROR flag was not also set in this image update, then
accessing any of the data in the image will restart the production
again, probably from the beginning.

See Also:
  • imageUpdate
/**
     * This flag in the infoflags argument to imageUpdate indicates that
     * an image which was being tracked asynchronously was aborted before
     * production was complete.  No more information will become available
     * without further action to trigger another image production sequence.
     * If the ERROR flag was not also set in this image update, then
     * accessing any of the data in the image will restart the production
     * again, probably from the beginning.
     * @see #imageUpdate
     */
    public static final int ABORT = 128;
}