Class Graphics

java.lang.Object
  |
  +--Graphics

public abstract class Graphics

extends java.lang.Object

Graphics is the abstract base class for all graphics contexts which allow an application to draw onto components realized on various devices or onto off-screen images. A Graphics object encapsulates the state information needed for the various rendering operations that Java supports. This state information includes:

• The Component to draw on
• A translation origin for rendering and clipping coordinates
• The current clip
• The current color
• The current font
• The current logical pixel operation function (XOR or Paint)
• The current XOR alternation color (see setXORMode)

Coordinates are infinitely thin and lie between the pixels of the output device. Operations which draw the outline of a figure operate by traversing along the infinitely thin path with a pixel-sized pen that hangs down and to the right of the anchor point on the path. Operations which fill a figure operate by filling the interior of the infinitely thin path. Operations which render horizontal text render the ascending portion of the characters entirely above the baseline coordinate.

Some important points to consider are that drawing a figure that covers a given rectangle will occupy one extra row of pixels on the right and bottom edges compared to filling a figure that is bounded by that same rectangle. Also, drawing a horizontal line along the same y coordinate as the baseline of a line of text will draw the line entirely below the text except for any descenders. Both of these properties are due to the pen hanging down and to the right from the path that it traverses.

All coordinates which appear as arguments to the methods of this Graphics object are considered relative to the translation origin of this Graphics object prior to the invocation of the method. All rendering operations modify only pixels which lie within the area bounded by both the current clip of the graphics context and the extents of the Component used to create the Graphics object.

Since:

JDK1.0

Constructor Summary

Graphics()

Method Summary

abstract void	dispose() Dispose of the system resources used by this graphics context.
abstract boolean	drawImage(Image img, int x, int y, ImageObserver observer) Draws as much of the specified image as is currently available with its northwest corner at the specified coordinate (x, y).
void	finalize() Disposes of this graphics context once it is no longer referenced.

Methods inherited from class java.lang.Object

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

Constructor Detail

Graphics

public Graphics()

Method Detail

drawImage

public abstract boolean drawImage(Image img,
                                  int x,
                                  int y,
                                  ImageObserver observer)

Draws as much of the specified image as is currently available with its northwest corner at the specified coordinate (x, y). This method will return 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 the method will return false and the indicated ImageObserver object will be notified as the conversion process progresses.

Parameters:

img - the image to be drawn

x - the x-coordinate of the northwest corner of the destination rectangle in pixels

y - the y-coordinate of the northwest corner of the destination rectangle in pixels

observer - the image observer to be notified as more of the image is converted. May be null

Returns:

true if the image is completely loaded and was painted successfully; false otherwise.

Since:

JDK1.0

See Also:

Image, ImageObserver

dispose

public abstract void dispose()

Dispose of the system resources used by this graphics context. The Graphics context cannot be used after being disposed of. While the finalization process of the garbage collector will also dispose of the same system resources, due to the number of Graphics objects that can be created in short time frames it is preferable to manually free the associated resources using this method rather than to rely on a finalization process which may not happen for a long period of time.

Graphics objects which are provided as arguments to the paint and update methods of Components are automatically disposed by the system when those methods return. Programmers should, for efficiency, call the dispose method when finished using a Graphics object only if it was created directly from a Component or another Graphics object.

Since:

JDK1.0

See Also:

#create, finalize(), Component#getGraphics, Component#paint, Component#update

finalize

public void finalize()

Disposes of this graphics context once it is no longer referenced.

Overrides:

finalize in class java.lang.Object

Since:

JDK1.0

See Also:

dispose()