Java (最新バージョン 6u23) で不透明なテキストをレンダリングするとサブピクセル AA がうまく使用されますが、半透明のテキストをレンダリングするとうまくいかないことがわかりました。
サブピクセル AA:
色だけが 0xFFFFFFFF から 0xBFFFFFFF に変更された同じテキスト:
ご覧のとおり、半透明のテキストは明らかに標準の AA であり、きれいな半透明のレンダリングではなく、90 年代の恐ろしい「蜘蛛の巣」のような外観になっています。
これは、一般的なサブピクセル AA の技術的な制限によるものですか、それとも Java のバグによるものですか、それとも単に Java が半透明のテキストを試みさえしないためですか、それとも何かを見逃したのでしょうか?
グラフィックの初期化
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
}
テキストのレンダリング
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; }
}
}