The Graphics
class is the abstract base class for all graphics
contexts that allow an application to draw onto components that are realized on
various devices, as well as onto off-screen images.
A Graphics
object encapsulates state information needed for the
basic rendering operations that Java supports. This state information includes
the following properties:
Component
object on which to draw.
setXORMode(java.awt.Color)
).
Coordinates are infinitely thin and lie between the pixels of the output device. Operations that draw the outline of a figure operate by traversing an infinitely thin path between pixels with a pixel-sized pen that hangs down and to the right of the anchor point on the path. Operations that fill a figure operate by filling the interior of that infinitely thin path. Operations that render horizontal text render the ascending portion of character glyphs entirely above the baseline coordinate.
The graphics pen hangs down and to the right from the path it traverses. This has the following implications:
All coordinates that 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 the current clip region, which is specified by a Shape
in user space and is controlled by the program using the Graphics
object. This user clip region is transformed into device space and combined with
the device clip region, which is defined by the visibility of windows and device
extents. The combination of the user clip region and device clip region defines the
composite clip region, which determines the final clipping region. The user clip region
cannot be modified by the rendering system to reflect the resulting composite
clip region. The user clip region can only be changed through the setClip
or
clipRect
methods. All drawing or writing is done in the current
color, using the current paint mode, and in the current font.
Method Detail |
public abstract Graphics create()
Graphics
object that is a copy of this
Graphics
object.
public Graphics create(int x, int y, int width, int height)
Graphics
object based on this
Graphics
object, but with a new translation and clip area. The
new Graphics
object has its origin translated to the specified
point (x, y). Its clip area is determined by the
intersection of the original clip area with the specified rectangle. The
arguments are all interpreted in the coordinate system of the original
Graphics
object. The new graphics context is identical to the
original, except in two respects:
0
, 0
) in the new
graphics context is the same as (x, y) in the original
graphics context.
0
, 0
), and its size is specified by the
width
and height
arguments. x
- the x coordinate.
y
- the y coordinate.
width
- the width of the clipping rectangle.
height
- the height of the clipping rectangle.
translate
, clipRect
public abstract void translate(int x, int y)
x
- the x coordinate.
y
- the y coordinate.public abstract Color getColor()
public abstract void setColor(Color c)
c
- the new rendering color.
public abstract void setPaintMode()
public abstract void setXORMode(Color c1)
When drawing operations are performed, pixels which are the current color are changed to the specified color, and vice versa.
Pixels that are of colors other than those two colors are changed in an unpredictable but reversible manner; if the same figure is drawn twice, then all pixels are restored to their original values.
c1
- the XOR alternation colorpublic abstract Font getFont()
public abstract void setFont(Font font)
font
- the font.
getFont()
,
drawString(java.lang.String,
int, int)
, drawBytes(byte[],
int, int, int, int)
, drawChars(char[],
int, int, int, int)
public FontMetrics getFontMetrics()
public abstract FontMetrics getFontMetrics(Font f)
f
- the specified font
public abstract Rectangle getClipBounds()
setClip(null)
, this method
returns null
. The coordinates in the rectangle are relative to
the coordinate system origin of this graphics context.
null
if no clip is set.
public abstract void clipRect(int x, int y, int width, int height)
setClip(null)
, the specified rectangle becomes the new clip. This
method sets the user clip, which is independent of the clipping associated
with device bounds and window visibility. This method can only be used to make
the current clip smaller. To set the current clip larger, use any of the
setClip methods. Rendering operations have no effect outside of the clipping
area.
x
- the x coordinate of the rectangle to intersect the clip
with
y
- the y coordinate of the rectangle to intersect the clip
with
width
- the width of the rectangle to intersect the clip
with
height
- the height of the rectangle to intersect the clip
with
setClip(int,
int, int, int)
, setClip(Shape)
public abstract void setClip(int x, int y, int width, int height)
x
- the x coordinate of the new clip rectangle.
y
- the y coordinate of the new clip rectangle.
width
- the width of the new clip rectangle.
height
- the height of the new clip rectangle.
clipRect
, setClip(Shape)
public abstract Shape getClip()
setClip(null)
, this method returns
null
.
Shape
object representing the current clipping area, or
null
if no clip is set.
getClipBounds()
,
clipRect(int,
int, int, int)
, setClip(int,
int, int, int)
, setClip(Shape)
public abstract void setClip(Shape clip)
Shape
interface can be used to set the clip.
The only Shape
objects that are guaranteed to be supported are
Shape
objects that are obtained via the getClip
method and via Rectangle
objects. This method sets the user clip,
which is independent of the clipping associated with device bounds and window
visibility.
clip
- the Shape
to use to set the clip
getClip
,
clipRect
, setClip
public abstract void copyArea(int x, int y, int width, int height, int dx, int dy)
dx
and dy
. From the point specified by x
and
y
, this method copies downwards and to the right. To copy an area
of the component to the left or upwards, specify a negative value for
dx
or dy
. If a portion of the source rectangle lies
outside the bounds of the component, or is obscured by another window or
component, copyArea
will be unable to copy the associated pixels.
The area that is omitted can be refreshed by calling the component's
paint
method.
x
- the x coordinate of the source rectangle.
y
- the y coordinate of the source rectangle.
width
- the width of the source rectangle.
height
- the height of the source rectangle.
dx
- the horizontal distance to copy the pixels.
dy
- the vertical distance to copy the
pixels.public abstract void drawLine(int x1, int y1, int x2, int y2)
(x1, y1)
and (x2, y2)
in this graphics
context's coordinate system.
x1
- the first point's x coordinate.
y1
- the first point's y coordinate.
x2
- the second point's x coordinate.
y2
- the second point's y
coordinate.public abstract void fillRect(int x, int y, int width, int height)
x
and x + width - 1
. The
top and bottom edges are at y
and
y + height - 1
. The resulting rectangle
covers an area width
pixels wide by height
pixels
tall. The rectangle is filled using the graphics context's current color.
x
- the x coordinate of the rectangle to be filled.
y
- the y coordinate of the rectangle to be filled.
width
- the width of the rectangle to be filled.
height
- the height of the rectangle to be filled.
clearRect
, drawRect
public void drawRect(int x, int y, int width, int height)
x
and x + width
. The
top and bottom edges are at y
and
y + height
. The rectangle is drawn using the graphics
context's current color.
x
- the x coordinate of the rectangle to be drawn.
y
- the y coordinate of the rectangle to be drawn.
width
- the width of the rectangle to be drawn.
height
- the height of the rectangle to be drawn.
fillRect
, clearRect
public abstract void clearRect(int x, int y, int width, int height)
Beginning with Java 1.1, the background color of offscreen images may
be system dependent. Applications should use setColor
followed by
fillRect
to ensure that an offscreen image is cleared to a
specific color.
x
- the x coordinate of the rectangle to clear.
y
- the y coordinate of the rectangle to clear.
width
- the width of the rectangle to clear.
height
- the height of the rectangle to clear.
fillRect
, drawRect
, setColor(java.awt.Color)
,
setPaintMode()
,
setXORMode(java.awt.Color)
public abstract void drawRoundRect(int x, int y, int width, int height, int arcWidth, int arcHeight)
x
and x + width
, respectively. The top and bottom edges
of the rectangle are at y
and y + height
.
x
- the x coordinate of the rectangle to be drawn.
y
- the y coordinate of the rectangle to be drawn.
width
- the width of the rectangle to be drawn.
height
- the height of the rectangle to be drawn.
arcWidth
- the horizontal diameter of the arc at the four
corners.
arcHeight
- the vertical diameter of the arc at the four
corners.
fillRoundRect
public abstract void fillRoundRect(int x, int y, int width, int height, int arcWidth, int arcHeight)
x
and
x + width - 1
, respectively. The top and
bottom edges of the rectangle are at y
and
y + height - 1
.
x
- the x coordinate of the rectangle to be filled.
y
- the y coordinate of the rectangle to be filled.
width
- the width of the rectangle to be filled.
height
- the height of the rectangle to be filled.
arcWidth
- the horizontal diameter of the arc at the four
corners.
arcHeight
- the vertical diameter of the arc at the four
corners.
drawRoundRect
public void draw3DRect(int x, int y, int width, int height, boolean raised)
The colors used for the highlighting effect are determined based on the
current color. The resulting rectangle covers an area that is
width + 1
pixels wide by
height + 1
pixels tall.
x
- the x coordinate of the rectangle to be drawn.
y
- the y coordinate of the rectangle to be drawn.
width
- the width of the rectangle to be drawn.
height
- the height of the rectangle to be drawn.
raised
- a boolean that determines whether the rectangle
appears to be raised above the surface or sunk into the surface.
fill3DRect
public void fill3DRect(int x, int y, int width, int height, boolean raised)
x
- the x coordinate of the rectangle to be filled.
y
- the y coordinate of the rectangle to be filled.
width
- the width of the rectangle to be filled.
height
- the height of the rectangle to be filled.
raised
- a boolean value that determines whether the
rectangle appears to be raised above the surface or etched into the surface.
draw3DRect
public abstract void drawOval(int x, int y, int width, int height)
x
, y
,
width
, and height
arguments.
The oval covers an area that is width + 1
pixels
wide and height + 1
pixels tall.
x
- the x coordinate of the upper left corner of the
oval to be drawn.
y
- the y coordinate of the upper left corner of the
oval to be drawn.
width
- the width of the oval to be drawn.
height
- the height of the oval to be drawn.
fillOval
public abstract void fillOval(int x, int y, int width, int height)
x
- the x coordinate of the upper left corner of the
oval to be filled.
y
- the y coordinate of the upper left corner of the
oval to be filled.
width
- the width of the oval to be filled.
height
- the height of the oval to be filled.
drawOval
public abstract void drawArc(int x, int y, int width, int height, int startAngle, int arcAngle)
The resulting arc begins at startAngle
and extends for
arcAngle
degrees, using the current color. Angles are interpreted
such that 0 degrees is at the 3 o'clock position. A positive value
indicates a counter-clockwise rotation while a negative value indicates a
clockwise rotation.
The center of the arc is the center of the rectangle whose origin is
(x, y) and whose size is specified by the
width
and height
arguments.
The resulting arc covers an area width + 1
pixels
wide by height + 1
pixels tall.
The angles are specified relative to the non-square extents of the bounding rectangle such that 45 degrees always falls on the line from the center of the ellipse to the upper right corner of the bounding rectangle. As a result, if the bounding rectangle is noticeably longer in one axis than the other, the angles to the start and end of the arc segment will be skewed farther along the longer axis of the bounds.
x
- the x coordinate of the upper-left corner of the
arc to be drawn.
y
- the y coordinate of the upper-left corner of the
arc to be drawn.
width
- the width of the arc to be drawn.
height
- the height of the arc to be drawn.
startAngle
- the beginning angle.
arcAngle
- the angular extent of the arc, relative to the
start angle.
fillArc
public abstract void fillArc(int x, int y, int width, int height, int startAngle, int arcAngle)
The resulting arc begins at startAngle
and extends for
arcAngle
degrees. Angles are interpreted such that 0 degrees
is at the 3 o'clock position. A positive value indicates a
counter-clockwise rotation while a negative value indicates a clockwise
rotation.
The center of the arc is the center of the rectangle whose origin is
(x, y) and whose size is specified by the
width
and height
arguments.
The resulting arc covers an area width + 1
pixels
wide by height + 1
pixels tall.
The angles are specified relative to the non-square extents of the bounding rectangle such that 45 degrees always falls on the line from the center of the ellipse to the upper right corner of the bounding rectangle. As a result, if the bounding rectangle is noticeably longer in one axis than the other, the angles to the start and end of the arc segment will be skewed farther along the longer axis of the bounds.
x
- the x coordinate of the upper-left corner of the
arc to be filled.
y
- the y coordinate of the upper-left corner of the
arc to be filled.
width
- the width of the arc to be filled.
height
- the height of the arc to be filled.
startAngle
- the beginning angle.
arcAngle
- the angular extent of the arc, relative to the
start angle.
drawArc
public abstract void drawPolyline(int[] xPoints, int[] yPoints, int nPoints)
xPoints
- an array of x points
yPoints
- an array of y points
nPoints
- the total number of points
drawPolygon
public abstract void drawPolygon(int[] xPoints, int[] yPoints, int nPoints)
This method draws the polygon defined by nPoint
line segments,
where the first nPoint - 1
line segments are line
segments from
(xPoints[i - 1], yPoints[i - 1])
to
(xPoints[i], yPoints[i])
, for
1 ≤ i ≤ nPoints
. The figure is
automatically closed by drawing a line connecting the final point to the first
point, if those points are different.
xPoints
- a an array of x
coordinates.
yPoints
- a an array of y
coordinates.
nPoints
- a the total number of points.
fillPolygon
, drawPolyline
public void drawPolygon(Polygon p)
Polygon
object.
p
- the polygon to draw.
fillPolygon
, drawPolyline
public abstract void fillPolygon(int[] xPoints, int[] yPoints, int nPoints)
This method draws the polygon defined by nPoint
line segments,
where the first nPoint - 1
line segments are line
segments from
(xPoints[i - 1], yPoints[i - 1])
to
(xPoints[i], yPoints[i])
, for
1 ≤ i ≤ nPoints
. The figure is
automatically closed by drawing a line connecting the final point to the first
point, if those points are different.
The area inside the polygon is defined using an even-odd fill rule, also known as the alternating rule.
xPoints
- a an array of x
coordinates.
yPoints
- a an array of y
coordinates.
nPoints
- a the total number of points.
drawPolygon
public void fillPolygon(Polygon p)
The area inside the polygon is defined using an even-odd fill rule, also known as the alternating rule.
p
- the polygon to fill.
drawPolygon
public abstract void drawString(String str, int x, int y)
str
- the string to be drawn.
x
- the x coordinate.
y
- the y coordinate.
drawBytes
, drawChars
public abstract void drawString(AttributedCharacterIterator iterator, int x, int y)
iterator
- the iterator whose text is to be drawn
x
- the x coordinate.
y
- the y coordinate.
drawBytes
, drawChars
public void drawChars(char[] data, int offset, int length, int x, int y)
data
- the array of characters to be drawn
offset
- the start offset in the data
length
- the number of characters to be drawn
x
- the x coordinate of the baseline of the text
y
- the y coordinate of the baseline of the text
drawBytes
, drawString
public void drawBytes(byte[] data, int offset, int length, int x, int y)
data
- the data to be drawn
offset
- the start offset in the data
length
- the number of bytes that are drawn
x
- the x coordinate of the baseline of the text
y
- the y coordinate of the baseline of the text
drawChars
, drawString
public abstract boolean drawImage(Image img, int x, int y, ImageObserver observer)
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.
If the image has not yet been completely loaded, then
drawImage
returns false
. As more of the image
becomes available, the process that draws the image notifies the specified
image observer.
img
- the specified image to be drawn.
x
- the x coordinate.
y
- the y coordinate.
observer
- object to be notified as more of the image is
converted.
public abstract boolean drawImage(Image img, int x, int y, int width, int height, ImageObserver observer)
The image is drawn inside the specified rectangle of this graphics context's coordinate space, and is scaled if necessary. Transparent pixels do not affect whatever pixels are already there.
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
drawImage
returns false
. As more of the image
becomes available, the process that draws the image notifies the image
observer by calling its imageUpdate
method.
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.
img
- the specified image to be drawn.
x
- the x coordinate.
y
- the y coordinate.
width
- the width of the rectangle.
height
- the height of the rectangle.
observer
- object to be notified as more of the image is
converted.
public abstract boolean drawImage(Image img, int x, int y, Color bgcolor, ImageObserver observer)
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.
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.
If the image has not yet been completely loaded, then
drawImage
returns false
. As more of the image
becomes available, the process that draws the image notifies the specified
image observer.
img
- the specified image to be drawn.
x
- the x coordinate.
y
- the y coordinate.
bgcolor
- the background color to paint under the
non-opaque portions of the image.
observer
- object to be notified as more of the image is
converted.
public abstract boolean drawImage(Image img, int x, int y, int width, int height, Color bgcolor, ImageObserver observer)
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.
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
drawImage
returns false
. As more of the image
becomes available, the process that draws the image notifies the specified
image observer.
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.
img
- the specified image to be drawn.
x
- the x coordinate.
y
- the y coordinate.
width
- the width of the rectangle.
height
- the height of the rectangle.
bgcolor
- the background color to paint under the
non-opaque portions of the image.
observer
- object to be notified as more of the image is
converted.
public abstract boolean drawImage(Image img, int dx1, int dy1, int dx2, int dy2, int sx1, int sy1, int sx2, int sy2, ImageObserver observer)
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
drawImage
returns false
. As more of the image
becomes available, the process that draws the image notifies the specified
image observer.
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.
img
- the specified image to be drawn
dx1
- the x coordinate of the first corner of the
destination rectangle.
dy1
- the y coordinate of the first corner of the
destination rectangle.
dx2
- the x coordinate of the second corner of the
destination rectangle.
dy2
- the y coordinate of the second corner of the
destination rectangle.
sx1
- the x coordinate of the first corner of the
source rectangle.
sy1
- the y coordinate of the first corner of the
source rectangle.
sx2
- the x coordinate of the second corner of the
source rectangle.
sy2
- the y coordinate of the second corner of the
source rectangle.
observer
- object to be notified as more of the image is
scaled and converted.
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)
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.
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
drawImage
returns false
. As more of the image
becomes available, the process that draws the image notifies the specified
image observer.
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.
img
- the specified image to be drawn
dx1
- the x coordinate of the first corner of the
destination rectangle.
dy1
- the y coordinate of the first corner of the
destination rectangle.
dx2
- the x coordinate of the second corner of the
destination rectangle.
dy2
- the y coordinate of the second corner of the
destination rectangle.
sx1
- the x coordinate of the first corner of the
source rectangle.
sy1
- the y coordinate of the first corner of the
source rectangle.
sx2
- the x coordinate of the second corner of the
source rectangle.
sy2
- the y coordinate of the second corner of the
source rectangle.
bgcolor
- the background color to paint under the
non-opaque portions of the image.
observer
- object to be notified as more of the image is
scaled and converted.
public abstract void dispose()
Graphics
object cannot be used after
dispose
has been called.
When a Java program runs, a large number of Graphics
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.
Graphics objects which are provided as arguments to the paint
and update
methods of components are automatically released by
the system when those methods return. For efficiency, programmers should call
dispose
when finished using a Graphics
object only
if it was created directly from a component or another Graphics
object.
public void finalize()
public String toString()
String
object representing this
Graphics
object's value.
public boolean hitClip(int x, int y, int width, int height)
x
- the x coordinate of the rectangle to test against the
clip
y
- the y coordinate of the rectangle to test against the
clip
width
- the width of the rectangle to test against the clip
height
- the height of the rectangle to test against the
clippublic Rectangle getClipBounds(Rectangle r)
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 setClip(null)
,
this method returns the specified Rectangle
.
r
- the rectangle where the current clipping area is copied
to. Any current values in this rectangle are overwritten.
Maintained by John Loomis, last updated 15 June 2000