graphics.java

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     * the image becomes available, the process that draws the image notifies 
     * the image observer by calling its <code>imageUpdate</code> method.
     * <p>
     * A scaled version of an image will not necessarily be
     * available immediately just because an unscaled version of the
     * image has been constructed for this output device.  Each size of
     * the image may be cached separately and generated from the original
     * data in a separate image production sequence.
     * @param    img    the specified image to be drawn.
     * @param    x      the <i>x</i> coordinate.
     * @param    y      the <i>y</i> coordinate.
     * @param    width  the width of the rectangle.
     * @param    height the height of the rectangle.
     * @param    observer    object to be notified as more of 
     *                          the image is converted.
     * @see      java.awt.Image
     * @see      java.awt.image.ImageObserver
     * @see      java.awt.image.ImageObserver#imageUpdate(java.awt.Image, int, int, int, int, int)
     * @since    JDK1.0
     */
    public abstract boolean drawImage(Image img, int x, int y,
        int width, int height, 
        ImageObserver observer);
    
    /** 
     * Draws as much of the specified image as is currently available.
     * The image is drawn with its top-left corner at 
     * (<i>x</i>,&nbsp;<i>y</i>) in this graphics context's coordinate 
     * space.  Transparent pixels are drawn in the specified
     * background color.
     * <p> 
     * This operation is equivalent to filling a rectangle of the
     * width and height of the specified image with the given color and then
     * drawing the image on top of it, but possibly more efficient.
     * <p>
     * This method returns immediately in all cases, even if the
     * complete image has not yet been loaded, and it has not been dithered 
     * and converted for the current output device.
     * <p>
     * If the image has not yet been completely loaded, then
     * <code>drawImage</code> returns <code>false</code>. As more of
     * the image becomes available, the process that draws the image notifies 
     * the specified image observer.
     * @param    img    the specified image to be drawn.
     * @param    x      the <i>x</i> coordinate.
     * @param    y      the <i>y</i> coordinate.
     * @param    bgcolor the background color to paint under the
     *                         non-opaque portions of the image.
     * @param    observer    object to be notified as more of 
     *                          the image is converted.
     * @see      java.awt.Image
     * @see      java.awt.image.ImageObserver
     * @see      java.awt.image.ImageObserver#imageUpdate(java.awt.Image, int, int, int, int, int)
     * @since    JDK1.0
     */
    public abstract boolean drawImage(Image img, int x, int y, 
        Color bgcolor,
        ImageObserver observer);

    /**
     * Draws as much of the specified image as has already been scaled
     * to fit inside the specified rectangle.
     * <p>
     * The image is drawn inside the specified rectangle of this 
     * graphics context's coordinate space, and is scaled if 
     * necessary. Transparent pixels are drawn in the specified
     * background color. 
     * This operation is equivalent to filling a rectangle of the
     * width and height of the specified image with the given color and then
     * drawing the image on top of it, but possibly more efficient.
     * <p>
     * This method returns immediately in all cases, even if the
     * entire image has not yet been scaled, dithered, and converted
     * for the current output device.
     * If the current output representation is not yet complete then
     * <code>drawImage</code> returns <code>false</code>. As more of
     * the image becomes available, the process that draws the image notifies 
     * the specified image observer.
     * <p>
     * A scaled version of an image will not necessarily be
     * available immediately just because an unscaled version of the
     * image has been constructed for this output device.  Each size of
     * the image may be cached separately and generated from the original
     * data in a separate image production sequence.
     * @param    img       the specified image to be drawn.
     * @param    x         the <i>x</i> coordinate.
     * @param    y         the <i>y</i> coordinate.
     * @param    width     the width of the rectangle.
     * @param    height    the height of the rectangle.
     * @param    bgcolor   the background color to paint under the
     *                         non-opaque portions of the image.
     * @param    observer    object to be notified as more of 
     *                          the image is converted.
     * @see      java.awt.Image
     * @see      java.awt.image.ImageObserver
     * @see      java.awt.image.ImageObserver#imageUpdate(java.awt.Image, int, int, int, int, int)
     * @since    JDK1.0
     */
    public abstract boolean drawImage(Image img, int x, int y,
        int width, int height, 
        Color bgcolor,
        ImageObserver observer);
    
    /**
     * Draws as much of the specified area of the specified image as is
     * currently available, scaling it on the fly to fit inside the
     * specified area of the destination drawable surface. Transparent pixels 
     * do not affect whatever pixels are already there.
     * <p>
     * This method returns immediately in all cases, even if the
     * image area to be drawn has not yet been scaled, dithered, and converted
     * for the current output device.
     * If the current output representation is not yet complete then
     * <code>drawImage</code> returns <code>false</code>. As more of
     * the image becomes available, the process that draws the image notifies 
     * the specified image observer.
     * <p>
     * This method always uses the unscaled version of the image
     * to render the scaled rectangle and performs the required
     * scaling on the fly. It does not use a cached, scaled version
     * of the image for this operation. Scaling of the image from source
     * to destination is performed such that the first coordinate
     * of the source rectangle is mapped to the first coordinate of
     * the destination rectangle, and the second source coordinate is
     * mapped to the second destination coordinate. The subimage is
     * scaled and flipped as needed to preserve those mappings.
     * @param       img the specified image to be drawn
     * @param       dx1 the <i>x</i> coordinate of the first corner of the
     *                    destination rectangle.
     * @param       dy1 the <i>y</i> coordinate of the first corner of the
     *                    destination rectangle.
     * @param       dx2 the <i>x</i> coordinate of the second corner of the
     *                    destination rectangle.
     * @param       dy2 the <i>y</i> coordinate of the second corner of the
     *                    destination rectangle.
     * @param       sx1 the <i>x</i> coordinate of the first corner of the
     *                    source rectangle.
     * @param       sy1 the <i>y</i> coordinate of the first corner of the
     *                    source rectangle.
     * @param       sx2 the <i>x</i> coordinate of the second corner of the
     *                    source rectangle.
     * @param       sy2 the <i>y</i> coordinate of the second corner of the
     *                    source rectangle.
     * @param       observer object to be notified as more of the image is
     *                    scaled and converted.
     * @see         java.awt.Image
     * @see         java.awt.image.ImageObserver
     * @see         java.awt.image.ImageObserver#imageUpdate(java.awt.Image, int, int, int, int, int)
     * @since       JDK1.1
     */
    public abstract boolean drawImage(Image img,
        int dx1, int dy1, int dx2, int dy2,
        int sx1, int sy1, int sx2, int sy2,
        ImageObserver observer);

    /**
     * Draws as much of the specified area of the specified image as is
     * currently available, scaling it on the fly to fit inside the
     * specified area of the destination drawable surface. 
     * <p>
     * Transparent pixels are drawn in the specified background color. 
     * This operation is equivalent to filling a rectangle of the
     * width and height of the specified image with the given color and then
     * drawing the image on top of it, but possibly more efficient.
     * <p>
     * This method returns immediately in all cases, even if the
     * image area to be drawn has not yet been scaled, dithered, and converted
     * for the current output device.
     * If the current output representation is not yet complete then
     * <code>drawImage</code> returns <code>false</code>. As more of
     * the image becomes available, the process that draws the image notifies 
     * the specified image observer.
     * <p>
     * This method always uses the unscaled version of the image
     * to render the scaled rectangle and performs the required
     * scaling on the fly. It does not use a cached, scaled version
     * of the image for this operation. Scaling of the image from source
     * to destination is performed such that the first coordinate
     * of the source rectangle is mapped to the first coordinate of
     * the destination rectangle, and the second source coordinate is
     * mapped to the second destination coordinate. The subimage is
     * scaled and flipped as needed to preserve those mappings.
     * @param       img the specified image to be drawn
     * @param       dx1 the <i>x</i> coordinate of the first corner of the
     *                    destination rectangle.
     * @param       dy1 the <i>y</i> coordinate of the first corner of the
     *                    destination rectangle.
     * @param       dx2 the <i>x</i> coordinate of the second corner of the
     *                    destination rectangle.
     * @param       dy2 the <i>y</i> coordinate of the second corner of the
     *                    destination rectangle.
     * @param       sx1 the <i>x</i> coordinate of the first corner of the
     *                    source rectangle.
     * @param       sy1 the <i>y</i> coordinate of the first corner of the
     *                    source rectangle.
     * @param       sx2 the <i>x</i> coordinate of the second corner of the
     *                    source rectangle.
     * @param       sy2 the <i>y</i> coordinate of the second corner of the
     *                    source rectangle.
     * @param       bgcolor the background color to paint under the
     *                    non-opaque portions of the image.
     * @param       observer object to be notified as more of the image is
     *                    scaled and converted.
     * @see         java.awt.Image
     * @see         java.awt.image.ImageObserver
     * @see         java.awt.image.ImageObserver#imageUpdate(java.awt.Image, int, int, int, int, int)
     * @since       JDK1.1
     */
    public abstract boolean drawImage(Image img,
        int dx1, int dy1, int dx2, int dy2,
        int sx1, int sy1, int sx2, int sy2,
        Color bgcolor,
        ImageObserver observer);

    /**
     * Disposes of this graphics context and releases 
     * any system resources that it is using. 
     * A <code>Graphics</code> object cannot be used after 
     * <code>dispose</code>has been called.
     * <p>
     * When a Java program runs, a large number of <code>Graphics</code>
     * objects can be created within a short time frame.
     * Although the finalization process of the garbage collector 
     * also disposes of the same system resources, it is preferable 
     * to manually free the associated resources by calling this
     * method rather than to rely on a finalization process which 
     * may not run to completion for a long period of time.
     * <p>
     * Graphics objects which are provided as arguments to the 
     * <code>paint</code> and <code>update</code> methods 
     * of components are automatically released by the system when 
     * those methods return. For efficiency, programmers should
     * call <code>dispose</code> when finished using
     * a <code>Graphics</code> object only if it was created 
     * directly from a component or another <code>Graphics</code> object.
     * @see         java.awt.Graphics#finalize
     * @see         java.awt.Component#paint
     * @see         java.awt.Component#update
     * @see         java.awt.Component#getGraphics
     * @see         java.awt.Graphics#create
     * @since       JDK1.0
     */
    public abstract void dispose();

    /**
     * Disposes of this graphics context once it is no longer referenced.
     * @see #dispose
     * @since JDK1.0
     */
    public void finalize() {
        dispose();
    }

    /**
     * Returns a <code>String</code> object representing this 
     *                        <code>Graphics</code> object's value.
     * @return       a string representation of this graphics context.
     * @since        JDK1.0
     */
    public String toString() {	
        return getClass().getName() + "[font=" + getFont() + ",color=" + getColor() + "]";
    }
    
    /**
     * Returns the bounding rectangle of the current clipping area.
     * The coordinates in the rectangle are relative to the coordinate
     * system origin of this graphics context.  This method differs
     * from {@link #getClipBounds() getClipBounds} in that an existing 
     * rectangle is used instead of allocating a new one.  
     * This method refers to the user clip, which is independent of the
     * clipping associated with device bounds and window visibility.
     *  If no clip has previously been set, or if the clip has been 
     * cleared using <code>setClip(null)</code>, this method returns the 
     * specified <code>Rectangle</code>.
     * @param  r    the rectangle where the current clipping area is
     *              copied to.  Any current values in this rectangle are
     *              overwritten.
     * @return      the bounding rectangle of the current clipping area.
     */
    public Rectangle getClipBounds(Rectangle r) {
        Rectangle clipRect = getClipBounds();
        if (clipRect == null) return r;
        if (r == null) return clipRect;
        r.x = clipRect.x;
        r.y = clipRect.y;
        r.width = clipRect.width;
        r.height = clipRect.height;
        return r;
    }    
}