We are trying to convert jpg images to a specific size. Because the huge amount
of pictures we decided to use the multi threaded approach with a backport of
the Java 1.5 Concurrency package. (We are still using 1.4 for production)
The application in our test environment runs on Java 1.5.0_05 and Apache Tomcat
5.5.20 on Linux.
Now for the real problem. I'm running the following code with 4 threads. I've
read that the Graphics2D code is not thread safe, so I've synchronized it.
However, the convert method hangs on the next thread dump:
"pool-1-thread-3" prio=1 tid=0x8c9b81a0 nid=0x1e56 runnable
[0x8a533000..0x8a5337f0]
at sun.java2d.loops.ScaledBlit.Scale(Native Method)
at sun.java2d.pipe.DrawImage.scaleSurfaceData(DrawImage.java:850)
at sun.java2d.pipe.DrawImage.renderImageScale(DrawImage.java:505)
at sun.java2d.pipe.DrawImage.tryCopyOrScale(DrawImage.java:287)
at sun.java2d.pipe.DrawImage.transformImage(DrawImage.java:171)
at sun.java2d.pipe.DrawImage.transformImage(DrawImage.java:947)
at sun.java2d.pipe.ValidatePipe.transformImage(ValidatePipe.java:212)
at sun.java2d.SunGraphics2D.drawImage(SunGraphics2D.java:2969)
at sun.java2d.SunGraphics2D.drawRenderedImage(SunGraphics2D.java:2392)
at test.ImageCallable.convert(ImageCallable.java:90)
The relevant code of the ImageCallable:
private static final Object GRAPHICS_MUTEX = new Object();
static {
ImageIO.setUseCache(false);
}
private boolean convert(final ImageFormat imageFormat, final BufferedImage
imageSource, final File destinationFile) {
Dimension imageSize = imageFormat.getDimension();
log.debug("Scaling image '" + relativeImageFile + "' to " +
imageSize.toString());
boolean success = true;
try {
BufferedImage bufferedImageDst = new BufferedImage(imageSize.width,
imageSize.height, BufferedImage.TYPE_INT_RGB);
double width = new
Double(bufferedImageDst.getWidth()).doubleValue() /
new Double(imageSource.getWidth()).doubleValue();
double height = new
Double(bufferedImageDst.getHeight()).doubleValue() /
new Double(imageSource.getHeight()).doubleValue();
AffineTransform transform = AffineTransform.getScaleInstance(width,
height);
//Native code behind drawRenderedImage is not thread safe.
synchronized (GRAPHICS_MUTEX) {
Graphics2D g = bufferedImageDst.createGraphics();
g.drawRenderedImage(imageSource, transform); // <- the problem
line
g.dispose();
}
success = ImageIO.write(bufferedImageDst,
imgFileSuffix.toUpperCase(), destinationFile);
} catch (Exception e) {
log.warn("Error scaling image '" + relativeImageFile + "' to " +
imageSize.toString());
success = false;
}
return success;
}
Has anybody any clue what is going wrong, and how I can fix it?
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http://forums.java.net/jive/thread.jspa?messageID=227409
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