Java可以使用亞像素AA渲染半透明文字嗎？

我發現雖然渲染Java中的不透明文本（最新版本6u23）使用子像素AA就好，但渲染半透明文本不會。Java可以使用亞像素AA渲染半透明文字嗎？

子像素AA：

alt text

用於僅僅顏色已經從0xFFFFFFFF的改變0xBFFFFFFF同樣的文字：

alt text

正如你所看到的，半透明的文字顯然是標準的AA，而不是一個乾淨的半透明渲染，它具有可怕的'90年代'蜘蛛俠'外觀。

這是由於一般的子像素AA的技術限制，或在Java中的一個bug，或者只是因爲Java甚至沒有嘗試爲半透明的文字，或有我錯過了什麼？

顯卡初始化

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 
    }

文本渲染

Object oaa=disableGeneralAA(gc); 
... 
gc.drawString(tl,xx,(ty+(xa*met.getHeight()))); 
restoreGeneralAA(gc,oaa); 

... 


static private volatile boolean   hasRenderingHints=true; 

// ***************************************************************************** 
// STATIC INIT & MAIN 
// ***************************************************************************** 

// ***************************************************************************** 
// STATIC METHODS 
// ***************************************************************************** 

/** 
* Disable the general anti-aliasing rendering hint, returning whether the old value was RenderingHints.VALUE_ANTIALIAS_ON. 
* <p> 
* 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. 
* <p> 
* 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 && val!=null) { 
     try { gc.setRenderingHint(RenderingHints.KEY_ANTIALIASING,val); } 
     catch(NoClassDefFoundError thr) { hasRenderingHints=false; } 
     catch(NoSuchFieldError  thr) { hasRenderingHints=false; } 
     catch(NoSuchMethodError thr) { hasRenderingHints=false; } 
     } 
    }

來源

2010-12-22 Lawrence Dol

您是否嘗試將抗鋸齒文本渲染到`BufferedImage`中，然後使用`AlphaComposite`將圖像半透明地繪製到屏幕上？（不幸的是，它會變慢） – finnw 2010-12-22 19:50:01

@finnw：所有的繪畫都是在屏幕外的BufferedImage上完成的，並且使用一個簡單的`gc.drawImage`將該圖像複製到每個`paint（Graphics agc）`的底層屏幕圖形上下文中。我希望屏幕外緩衝區中的圖像是最終圖像;我做了很多半透明的繪畫，唯一的問題是當文本顏色是半透明的時候，文本渲染似乎是標準AA。 – 2010-12-22 20:29:15

看起來這是一段時間的問題http://forums.java.net/node/676951 – z5h 2011-01-11 16:11:05