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POCan Java render translucent text using sub-pixel AA?
 

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  1. POCan Java render translucent text using sub-pixel AA?
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    <p>I have found that while rendering opaque text in Java (latest version 6u23) uses sub-pixel AA just fine, rendering translucent text does not.</p> <p>Sub-pixel AA:</p> <p><img src="https://i.stack.imgur.com/ed1l4.gif" alt="alt text"> <img src="https://i.stack.imgur.com/oEDgp.gif" alt="alt text"></p> <p>The same text for which only the color has been changed from 0xFFFFFFFF to 0xBFFFFFFF:</p> <p><img src="https://i.stack.imgur.com/mfQky.gif" alt="alt text"> <img src="https://i.stack.imgur.com/F3rlJ.gif" alt="alt text"></p> <p>As you can see, the translucent text is clearly standard AA and rather than a clean translucent rendering, it has that awful '90s "spidery" appearance.</p> <p>Is this due to a technical limitation for sub-pixel AA in general, or a bug in Java, or just because Java doesn't even try for translucent text, or have I missed something?</p> <hr> <p><strong>Graphics Initialization</strong></p> <pre><code>dbGraphics=(Graphics2D)dbImage.getGraphics(); if(dctRoot.properties.getBoolean("Antialias",true)) { try { Map hnts=(Map)(dctRoot.awtComponent.getToolkit().getDesktopProperty("awt.font.desktophints")); // SET AA ON OVERALL (NOTE: GENERAL AA MUST BE OFF FOR SUBPIXEL AA TO BE HONORED - TEXT WIDGETS MUST DO THIS THEMSELVES) dbGraphics.setRenderingHint(RenderingHints.KEY_ANTIALIASING,RenderingHints.VALUE_ANTIALIAS_ON); if(hnts!=null) { // SET FONT RENDERING HINTS FROM DESKTOP dbGraphics.addRenderingHints(hnts); } else { try { // SET TEXT AA TO FONT-SPECIFIED GASP AA (JAVA 6+) dbGraphics.setRenderingHint(RenderingHints.KEY_TEXT_ANTIALIASING,RenderingHints.class.getField("VALUE_TEXT_ANTIALIAS_GASP").get(null)); } catch(Throwable thr3) { // SET TEXT AA TO DEFAULT dbGraphics.setRenderingHint(RenderingHints.KEY_TEXT_ANTIALIASING,RenderingHints.VALUE_TEXT_ANTIALIAS_ON); } } } catch(Throwable thr) { dctRoot.log.println("Antialiasing not supported on this JVM ("+thr+")."); dctRoot.setProperty("Antialias","False"); // turn off AA for subsequent painting } } else { try { dbGraphics.setRenderingHint(RenderingHints.KEY_ANTIALIASING,RenderingHints.VALUE_ANTIALIAS_OFF); dbGraphics.setRenderingHint(RenderingHints.KEY_TEXT_ANTIALIASING,RenderingHints.VALUE_TEXT_ANTIALIAS_OFF); } catch(Throwable thr) {;} // ignore exception } </code></pre> <p><strong>Text Rendering</strong></p> <pre><code>Object oaa=disableGeneralAA(gc); ... gc.drawString(tl,xx,(ty+(xa*met.getHeight()))); restoreGeneralAA(gc,oaa); ... static private volatile boolean hasRenderingHints=true; // ***************************************************************************** // STATIC INIT &amp; MAIN // ***************************************************************************** // ***************************************************************************** // STATIC METHODS // ***************************************************************************** /** * Disable the general anti-aliasing rendering hint, returning whether the old value was RenderingHints.VALUE_ANTIALIAS_ON. * &lt;p&gt; * This method is needed for text rendering due to a bug in AWT; as of Java 6_20 when general AA is on text is not rendered using subpixel * AA, so general AA has to be turned off before rendering text and turned back on when done. This method abstracts that work and deals * with the possibility that the JVM does not support rendering hints, such as is the case with JME JVMs. */ static public Object disableGeneralAA(Graphics2D gc) { Object old=null; if(hasRenderingHints) { try { old=gc.getRenderingHint(RenderingHints.KEY_ANTIALIASING); gc.setRenderingHint(RenderingHints.KEY_ANTIALIASING,RenderingHints.VALUE_ANTIALIAS_OFF); } catch(NoClassDefFoundError thr) { hasRenderingHints=false; } catch(NoSuchFieldError thr) { hasRenderingHints=false; } catch(NoSuchMethodError thr) { hasRenderingHints=false; } } return old; } /** * Disable the general anti-aliasing rendering hint, returning whether the old value was RenderingHints.VALUE_ANTIALIAS_ON. * &lt;p&gt; * This method is needed for text rendering due to a bug in AWT; as of Java 6_20 when general AA is on text is not rendered using subpixel * AA, so general AA has to be turned off before rendering text and turned back on when done. This method abstracts that work and deals * with the possibility that the JVM does not support rendering hints, such as is the case with JME JVMs. */ static public void restoreGeneralAA(Graphics2D gc, Object val) { Object old=null; if(hasRenderingHints &amp;&amp; val!=null) { try { gc.setRenderingHint(RenderingHints.KEY_ANTIALIASING,val); } catch(NoClassDefFoundError thr) { hasRenderingHints=false; } catch(NoSuchFieldError thr) { hasRenderingHints=false; } catch(NoSuchMethodError thr) { hasRenderingHints=false; } } } </code></pre>
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    1. COHave you tried rendering antialiased text into a `BufferedImage` then using an `AlphaComposite` to draw the image translucently onto the screen? (It will be slower, unfortunately.)
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    2. CO@finnw: All painting is done to an offscreen BufferedImage, and that image is copied to the underlying screen graphics context on each `paint(Graphics agc)` using a simple `gc.drawImage`. I expect the image in the offscreen buffer to be the final image; I do lot's of translucent painting, and the only issue is that text rendering seems to be standard AA when the text color is translucent.
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      1. POCan Java render translucent text using sub-pixel AA?
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    3. COLooks like this has been an issue for a while http://forums.java.net/node/676951
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