Effective Java2D

June 6th, 2008

This post summarizes the changes that were made in Substance 5 to address the performance issues raised by the users. As mentioned before (part 1 and part 2), Substance 5 is 2.5-3.5 times faster than Substance 4.3 on various static and dynamic scenarios. Many thanks go to Dmitri Trembovetski from Java2D team for his help and tips.

  1. Use multi-stop gradients (LinearGradientPaint) with REPEAT cycle method (as mentioned in the comments on Romain’s blog entry).
  2. Rendering translucent texts is slow and does not use the new native font rasterizer in 6u10. Solution – instead of installing a translucent composite, interpolate the text foreground color and the background fill color based on your alpha value, and use full opacity text rendering.
  3. BufferedImage.setRGB and BufferedImage.getRGB are really slow. A custom BufferedImageOp might be more difficult to learn, but is much more performant if done correctly.
  4. Set RenderingHints.KEY_ANTIALIASING to OFF before calling any Graphics.fill operation that results in aliased fill in any case. This is especially relevant for Graphics.fillRect that gets integer parameters. Java2D is not smart enough (yet) to choose the non-antialiased path when the end result is non-antialiased.
  5. Intermediate non-cached BufferedImages are slow. Whenever possible, either draw directly on the Graphics context, or collect the final result into one BufferedImage that goes into the cache, even if the cache key is more complex.
  6. Filling with translucent color or filling under translucent composite is very expensive. In fact, the single largest performance gain (20% of the final result) in Substance 5 was removing watermarks from most core skins.
  7. Use AffineTransform for rotating painting instead of doing it manually. As with BufferedImageOp, it takes some time to understand how to do it (and i’m still terrible at it), but the performance is much better.
  8. Use EnumSet and EnumMap whenever possible. This is not Java2D-specific, and the tip goes to Joshua Bloch. These are quite faster than Hash* counterparts.
  9. Do not do multiplt rendering of the same surfaces. This is especially relevant for tables thatcan have potentially thousands of visible cells on the screen. Try to draw background fills and gradients once per table.
  10. Last, and not specific to Java2D – profile every scenario, question every method and every line of code.

More tips on Java2D performance right here.

Update: hitting “Submit” too fast, i forgot another Swing-specific optimization. Since everything UI-relates has to run on EDT, you can use non-synchronized non-thread safe code and collections. This comes in quite handy coupled with caching images and additional otherwise guarded blocks.