java 尽快清除透明的 BufferedImage
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Clear a transparent BufferedImage as fast as possible
提问by adrian.tarau
I have a transparent BufferedImage created with the following code(not relevant how it is created, I think):
我有一个使用以下代码创建的透明 BufferedImage（我认为与它的创建方式无关）：
GraphicsEnvironment ge = GraphicsEnvironment.getLocalGraphicsEnvironment();
GraphicsDevice gs = ge.getDefaultScreenDevice();
GraphicsConfiguration gc = gs.getDefaultConfiguration();
Rectangle screen = transformationContext.getScreen();
// Create an image that supports transparent pixels
return gc.createCompatibleImage((int) screen.getWidth(), (int) screen.getHeight(),
Transparency.BITMASK);
How do I clear the image(empty image in the same state as it was created) in the fastest way possible without recreating the image? Recreating the image puts a burden on GC, pausing the VM and freezing the UI.
如何在不重新创建图像的情况下以最快的方式清除图像（与创建时处于相同状态的空图像）？重新创建图像会给 GC 带来负担，暂停 VM 并冻结 UI。
回答by adrian.tarau
Got it :) used clearRect instead of fill with a transparent color.
明白了 :) 使用 clearRect 而不是填充透明颜色。
graphics = (Graphics2D) offlineBuffer.getGraphics();
graphics.setBackground(new Color(255, 255, 255, 0));
Rectangle screen = transformationContext.getScreen();
graphics.clearRect(0,0, (int)screen.getWidth(), (int)screen.getHeight());
回答by SyntaxT3rr0r
One relatively fast way, but I don't know if it's the fastest (and I'd like to see other answers) is to have another picture that you never modify and that is always "fully cleared" / "fully transparent" and then you do a raster copy, say you named that copy CLEAR:
一种相对较快的方法，但我不知道它是否是最快的（我想看到其他答案）是拥有另一张永远不会修改的图片，并且始终“完全清除”/“完全透明”，然后你做了一个光栅副本，假设你将该副本命名为 CLEAR：
imageYouWantToClear.setData( CLEAR.getRaster() );
Note that working with graphics can be very tricky when it comes to performances because there are a lot of not-very-well-documented behavior. For example your images (say the CLEAR one) maybe hardware-accelerated but you'd then lose hardware-acceleration as soon as you'd use a mutating method (like say a setRgb()) and it would prove very difficult to realize that you just lost the benefit of hardware acceleration.
请注意，当涉及到性能时，处理图形可能会非常棘手，因为有很多没有很好记录的行为。例如，您的图像（例如 CLEAR 图像）可能是硬件加速的，但是一旦您使用变异方法（例如setRgb()），您就会失去硬件加速，并且很难实现你刚刚失去了硬件加速的好处。
I think that the best place to find infos on the subject of performant BufferedImage would be in the Java game-programmers and Java game-API-programmers community/forums.
我认为在 Java game-programmers 和 Java game-API-programmers 社区/论坛中找到有关高性能 BufferedImage 主题的信息的最佳位置。
Btw make sure that both your BufferedImage are using the 'compatible' mode: TYPE_INT_ARGB may be fine on Windows but not on OS X, etc. so you want to create them doing something like:
顺便说一句，请确保您的 BufferedImage 都使用“兼容”模式：TYPE_INT_ARGB 在 Windows 上可能没问题，但在 OS X 等上可能没问题，所以您想创建它们，执行以下操作：
GraphicsEnvironment.getLocalGraphicsEnvironment().getDefaultScreenDevice().getDefaultConfiguration().createCompatibleImage(width, height, Transparency.TRANSLUCENT);
Ouch the Law-of-Demeter hurts, thanks Java ;)
哎哟迪米特法则很伤人，感谢 Java ;)
