BufferedImage reducedImage = new BufferedImage(newX, newY, BufferedImage.TYPE_INT_RGB);
Graphics2D g = reducedImage.createGraphics();
g.drawImage(originalImage, 0, 0, newX, newY, 0, 0, originalImage.getWidth(), originalImage.getHeight(), null);
Although not blazing fast, this is enough for many applications. I could reduce a 7 Mega-Pixels image to something like 250 pixels wide in about one second, or less, in my PowerBook G4. But this was in Tiger.
In Leopard, as some of you may have noticed (and if you have applications deployed on Leopard Server, be aware) this is incredibly slow. When I say slow, I say five minutes, or even more, with the CPU being used at 100% during that time.
There are two reasons that lead to this. The first (which is not a problem in itself, but it’s a cause of the problem): Apple switched from Quartz to Sun2D graphics engine as the default one for Java applications on Leopard. So, all your image manipulation is being done using the Sun pipeline now. This would not be a problem, except for the second reason:
the Apple JVM implementation has a bug that is slowing Sun’s pipeline drawImage method to a crawl. Actually, that was not the real reason. I testes this on FreeBSD (using Diablo JDK) and the speed was similar to Leopard’s. Sun2D is REALLY slow, to the point of being useless. I’m now using ImageMagick.
The only solution for now is forcing the application to use Quartz engine. You can do that using the command line option -Dapple.awt.graphics.UseQuartz=true. And, of course, file a bug on this!
Also, If you’re deploying on OSX, you can use sips (which I found to be a little faster).