How can I inherit the system's anti-alias setting for painting text to off-screen images like swing does?

Question

When I run my swing GUI applications under Java 6, they automatically use my configured sub-pixel anti-alias settings for all fonts. The result is much improved over standard A

Answer 1

java.awt.Toolkit.getDesktopProperty("awt.font.desktophints") appears to be null on linux, at least without any special vm command line options, presumably because it's unable to figure out what the platform defaults are.. adding e.g "-Dawt.useSystemAAFontSettings=lcd" seems to cure it and enables subpixel rendering if you set the hints on your Graphics2D instance.

Answer 2

Using Swing, I'm able to get the right text anti-aliasing hint like this:

JLabel label = new JLabel();
FontMetrics fm  = label.getFontMetrics( label.getFont() );
Object aaHintValue = fm.getFontRenderContext().getAntiAliasingHint();

On my system this returns RenderingHits.VALUE_TEXT_ANTIALIAS_LCD_HRGB.

Answer 3

Wait, are you running this code on a Windows JVM? I thought ClearType was a Microsoft technology that Swing inherits through some native code (ie, not available on Linux or other non Microsoft platforms).

I once wrote a servlet that generated JPGs with anti aliased fonts that ran on Debian, and this was the code I used

Font font = new Font("Komix", Font.PLAIN, 8);
Graphics2D g2;
g2.setRenderingHint(RenderingHints.KEY_ANTIALIASING, RenderingHints.VALUE_ANTIALIAS_ON);
FontRenderContext  frc = g2.getFontRenderContext();
g2.setFont(font);
g2.setPaint(Color.black);
g2.drawString(sMessage, xOffset, yOffset);

Offhand I can't recall if any of this code relies on Swing (I imported javax.swing and the servlet is about 300 lines long, so I may have thought I needed it for something else), a quick check on Google looks like this is squarely in the AWT space. Hope that helps.

Answer 4

I found there were a few factors going on here.

First, the image needs to be created from the underlying AWT component, and it must be created without transparency:

cfg.createCompatibleImage(wid,hgt);

instead of

cfg.createCompatibleImage(wid,hgt,Transparency.TRANSLUCENT);

Second, for some inexplicable reason, the primary AA setting, KEY_ANTIALIASING, must be off to use LCD subpixel AA.

Lastly, and most importantly, the desktop font rendering hints are easily retrieved using:

java.awt.Toolkit.getDesktopProperty("awt.font.desktophints")

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Update 2010-01-05

Retesting in Java 6.26, it seems like the problem with needing to set general AA off to render text AA has finally been resolved (way to go Oracle... after Sun was just a few years decade too late).