Java Reference
In-Depth Information
Discussion
The
imageio
package provides
java.awt.image.BufferedImage
to represent an image in
memory. It's a subclass of
java.awt.Image
, so normal graphics methods can be applied to
it, starting with
getGraphics()
. The static
ImageIO
methods
read()
and
write()
can be
used to load and store a
BufferedImage
.
The program shown here uses these methods to create the original versions of the circled
6/7/8 images that are used throughout this topic to indicate the version of Java needed to run
a particular code fragment, starting with a single coffee cup image created by artist
TikiGiki
and provided under the Creative Commons license from
http://OpenClipArt.org
.
ing Centered Text in a Component
in that it measures the actual width of the characters being
drawn. This plus a bit of simple arithmetic lets us put the large black version number (
6
in
this example) on top of the coffee cup, then we save the updated image to a file on disk;
shows the complete code for generating the image.
Example 12-6. ReadWriteImage.java
int
int
v
=
6
;
BufferedImage image
=
ImageIO
.
read
(
new
new
File
(
dir
+
"coffeecup.png"
));
Graphics2D g
=
image
.
createGraphics
();
Font f
=
new
new
Font
(
"Serif"
,
Font
.
BOLD
,
160
);
g
.
setFont
(
f
);
g
.
setColor
(
Color
.
black
);
String bigNumberLabel
=
Integer
.
toString
(
v
);
Rectangle2D lineMetrics
=
f
.
getStringBounds
(
bigNumberLabel
,
g
.
getFontRenderContext
() );
int
int
x
= (
int
int
) ((
image
.
getWidth
() -
lineMetrics
.
getWidth
() ) /
2
);
x
-=
10
;
// ad-hoc fudge factor
int
int
y
= (
int
int
) ((
image
.
getHeight
() +
lineMetrics
.
getHeight
()) /
2
);
g
.
drawString
(
bigNumberLabel
,
x
,
y
);
ImageIO
.
write
(
image
,
"png"
,
new
new
File
(
String
.
format
(
"%sjava%d.png"
,
dir
,
v
)));
The code needs to end with
System.exit(0);
because the graphics code starts a background
thread.
See Also
