Java可以使用子像素AA渲染半透明文本吗? [英] Can Java render translucent text using sub-pixel AA?
问题描述
我发现虽然在Java中渲染不透明文本(最新版本6u23)使用子像素AA就好了,渲染半透明文本却没有。
I have found that while rendering opaque text in Java (latest version 6u23) uses sub-pixel AA just fine, rendering translucent text does not.
子像素AA:
同样的文字,其中只有颜色已从0xFFFFFFFF到0xBFFFFFFF:
The same text for which only the color has been changed from 0xFFFFFFFF to 0xBFFFFFFF:
如您所见,半透明文字清晰明了标准AA而不是干净的半透明渲染,它具有可怕的'90年代蜘蛛外观。
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.
这是否是由于子像素AA的技术限制,或Java中的错误,或者只是因为Java甚至没有尝试半透明文本,或者我错过了什么?
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?
图形初始化on
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
}
文字渲染
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; }
}
}
推荐答案
从这些错误报告中可以看出,似乎没有(完全)支持向透明背景渲染文本:
It seems rendering text to a transparant background is not (fully) supported, as can be seen from these bugreports:
- http://bugs.sun.com/bugdatabase/view_bug.do?bug_id=6728834
- http://bugs.sun .com / bugdatabase / view_bug.do?bug_id = 6749060
- http://bugs.sun.com/bugdatabase/view_bug.do?bug_id=6749069
- http://bugs.sun.com/bugdatabase/view_bug.do?bug_id=6728834
- http://bugs.sun.com/bugdatabase/view_bug.do?bug_id=6749060
- http://bugs.sun.com/bugdatabase/view_bug.do?bug_id=6749069
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