使用 Graphics2D 填充透明度
我创建了一个 ARGB BufferedImage。现在我想用透明背景重新初始化它。我尝试了以下代码：
(...)
if( this.offscreen==null ||
this.offscreen.getWidth()!= dim.width ||
this.offscreen.getHeight()!= dim.height )
{
this.offscreen=new BufferedImage(
dim.width,
dim.height,
BufferedImage.TYPE_INT_ARGB);
}
Graphics2D g=this.offscreen.createGraphics();
g.setColor(new Color(255,255,255,0));
g.clearRect(0, 0, dim.width, dim.height);
(...)
但它不起作用。
请问您知道如何执行此操作吗？
谢谢 ！
I created an ARGB BufferedImage. Now I'd like to reinitialize it with a transparent background. I tried the following code:
(...)
if( this.offscreen==null ||
this.offscreen.getWidth()!= dim.width ||
this.offscreen.getHeight()!= dim.height )
{
this.offscreen=new BufferedImage(
dim.width,
dim.height,
BufferedImage.TYPE_INT_ARGB);
}
Graphics2D g=this.offscreen.createGraphics();
g.setColor(new Color(255,255,255,0));
g.clearRect(0, 0, dim.width, dim.height);
(...)
but it didn't work.
Any idea on how to do this please ?
Thanks !
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g.clearRect(..)使用Graphics2D对象的背景颜色填充选定的矩形。您最好执行g.fillRect(..)这将为您的代码提供预期结果，或者预先设置Graphics2D对象的背景颜色 (g.setBackground(..))。另外，您可能必须在填充之前执行
g.setComposite(AlphaComposite.getInstance(AlphaComposite.SRC));，以便正确设置缓冲区（忽略目标缓冲区数据，仅使用源数据 -在本例中为填充操作）。不确定该值的默认值是什么，但您应该稍后将其设置回该值以确保正常运行。g.clearRect(..)fills the selected rectangle with the background colour of theGraphics2Dobject. You're better off doingg.fillRect(..)which would give the intended result with your code, or set the background colour of theGraphics2Dobject beforehand (g.setBackground(..)).Also, you may have to do
g.setComposite(AlphaComposite.getInstance(AlphaComposite.SRC));before the fill so that it sets the buffer properly (ignore destination buffer data, only use source data -- in this case, the fill operation). Not sure what the default is for this value, but you should set it back to that afterwards to ensure proper operation.我以前遇到过这个问题，我用一个非常狭窄的技巧解决了它。
事情是这样的：
在 Paint 类的构造函数中拍摄系统的屏幕截图，但要小心
以及要清除屏幕的位置
I had this problem before and I solved it with a really narrow trick.
Here is the deal:
In the constructor of the paint Class take a screen shot of the System but be careful
And where you want to clear the screen