小编典典

我想说(希望这样做会带来更好的性能)，也许，如果您愿意采用这种Image方法，则最好创建一个尺寸为1x1像素的图像，然后转换其创建的图形以匹配所请求的图形点。并将此图像重新用于相同Component(甚至GraphicsConfiguration)的后续采样。

我通过创建以下方法进行了一些性能测试：

所谓的一种方法，getColorAtClipped它设置的创建剪辑Graphics的的Image要绘制所以并不是所有操作都有。

一种称为的方法getColorAtRelocation，该方法将组件的位置临时设置在需要采样的位置，然后(实际上使其更快)创建尺寸为1x1的图像并在其上绘制父对象。尽管此方法对于Swing而言并不是真正的线程安全方法，因为它需要设置Component来回的位置。它还要求printAll父级Container，这意味着Component要绘制更多。

然后调用一种方法getColorAtTranslation，该方法创建一个1x1图像并转换其Graphics实例，以便所需的位置实际上将绘制在(0,0)处，这是图像中真正的唯一像素。事实证明，对于这前三种方法，该方法是最快的。

那么，为什么不为以后的样本重用相同的资源呢？…这导致我进入最终方法：一个包含所有参与样本的必需资源的类：ComponentColorSampler在以下代码中调用的一个类

测试代码：

本节中的代码用于测试上述方法的性能。如果不正确，请在评论中让我知道，但是请注意，我对每种方法进行了大约300万次采样，以期避免附带的延迟。测试方法的每百万个样本中，我会打印一些时间，然后重新启动该过程以测试另外一百万个，最多3个。

import java.awt.Color;
import java.awt.Component;
import java.awt.Dimension;
import java.awt.Graphics;
import java.awt.Graphics2D;
import java.awt.Point;
import java.awt.image.BufferedImage;
import java.lang.reflect.InvocationTargetException;
import java.util.Objects;
import java.util.function.IntBinaryOperator;
import java.util.function.Supplier;
import javax.swing.JFrame;
import javax.swing.JPanel;
import javax.swing.SwingUtilities;
public class Main {
public static Color getColorAtClipped(final Component comp, final Point p) {
final BufferedImage bimg = comp.getGraphicsConfiguration().createCompatibleImage(comp.getWidth(), comp.getHeight());
final Graphics2D g2d = (Graphics2D) bimg.createGraphics();
g2d.setClip(p.x, p.y, 1, 1);
comp.printAll(g2d);
g2d.dispose();
final Color c = new Color(bimg.getRGB(p.x, p.y), true);
bimg.flush();
return c;
}
public static Color getColorAtRelocation(final Component comp, final Point p) {
final Point loc = comp.getLocation();
final BufferedImage bimg = comp.getGraphicsConfiguration().createCompatibleImage(1, 1);
comp.setLocation(loc.x - p.x, loc.y - p.y);
final Graphics2D g2d = (Graphics2D) bimg.createGraphics();
//g2d.setClip(0, 0, 1, 1);
comp.getParent().printAll(g2d);
comp.setLocation(loc);
g2d.dispose();
final Color c = new Color(bimg.getRGB(0, 0), true);
bimg.flush();
return c;
}
public static Color getColorAtTranslation(final Component comp, final Point p) {
final BufferedImage bimg = comp.getGraphicsConfiguration().createCompatibleImage(1, 1);
final Graphics2D g2d = (Graphics2D) bimg.createGraphics();
g2d.translate(-p.x, -p.y);
//g2d.setClip(0, 0, 1, 1);
comp.printAll(g2d);
g2d.dispose();
final Color c = new Color(bimg.getRGB(0, 0), true);
bimg.flush();
return c;
}
public static class ComponentColorSampler implements AutoCloseable, IntBinaryOperator, Supplier {
private final C comp;
private final BufferedImage bimg;
private final Graphics2D g2d;
private int x, y;
public ComponentColorSampler(final C comp) {
this.comp = Objects.requireNonNull(comp);
bimg = comp.getGraphicsConfiguration().createCompatibleImage(1, 1);
g2d = bimg.createGraphics();
//g2d.setClip(0, 0, 1, 1);
x = y = 0;
}
@Override
public C get() {
return comp;
}
@Override
public int applyAsInt(final int x, final int y) {
g2d.clearRect(0, 0, 1, 1);
g2d.translate(this.x - x, this.y - y);
this.x = x;
this.y = y;
comp.printAll(g2d);
return bimg.getRGB(0, 0);
}
public Color sample(final int x, final int y) {
return new Color(applyAsInt(x, y), true);
}
@Override
public void close() {
g2d.dispose();
bimg.flush();
}
}
public static class DrawPanel extends JPanel {
private final int x, y;
private Color c;
public DrawPanel(final int x, final int y) {
this.x = x;
this.y = y;
c = Color.BLUE;
}
@Override
protected void paintComponent(final Graphics g) {
super.paintComponent(g);
g.setColor(c);
g.fillRect(x, y, 1, 1);
}
public void setColor(final Color c) {
this.c = Objects.requireNonNull(c);
paintImmediately(0, 0, getWidth(), getHeight()); //Not sure yet.
repaint(); //Just to be sure now.
}
}
//@SuppressWarnings("SleepWhileInLoop")
public static boolean checkValid(final DrawPanel dp, final Supplier sampler) throws InterruptedException, InvocationTargetException {
for (final Color c: new Color[]{Color.BLUE, Color.RED, Color.BLACK, Color.WHITE, Color.BLACK, Color.CYAN}) {
SwingUtilities.invokeAndWait(() -> dp.setColor(c));
Thread.sleep(250); //Let it some time to change (not sure if needed).
if (!Objects.equals(c, sampler.get()))
return false;
}
return true;
}
public static long checkTime(final Supplier sampler) {
final long start = System.currentTimeMillis();
for (int i = 0; i < 1000000; ++i)
sampler.get();
return System.currentTimeMillis() - start;
}
public static void main(final String[] args) throws InterruptedException, InvocationTargetException {
final Point p = new Point(100, 100);
final DrawPanel contents = new DrawPanel(p.x, p.y);
contents.setPreferredSize(new Dimension(200, 200));
final JFrame frame = new JFrame("Printed!");
frame.setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);
frame.getContentPane().add(contents);
frame.pack();
frame.setLocationRelativeTo(null);
frame.setResizable(false);
frame.setVisible(true);
final ComponentColorSampler sampler = new ComponentColorSampler<>(contents);
final Supplier clipped = () -> getColorAtClipped(contents, p),
relocation = () -> getColorAtRelocation(contents, p),
translation = () -> getColorAtTranslation(contents, p),
samplerSampler = () -> sampler.sample(p.x, p.y);
System.out.println("#### Validity checks...");
for (int i = 0; i < 3; ++i) {
System.out.println("Batch " + (i + 1) + ':');
System.out.println("> Clipped: " + checkValid(contents, clipped) + '.');
System.out.println("> Relocation: " + checkValid(contents, relocation) + '.');
System.out.println("> Translation: " + checkValid(contents, translation) + '.');
System.out.println("> Sampler: " + checkValid(contents, samplerSampler) + '.');
}
System.out.println("#### Timings...");
for (int i = 0; i < 3; ++i) {
System.out.println("Batch " + (i + 1) + ':');
System.out.println("> Clipped: " + checkTime(clipped) + "ms.");
System.out.println("> Relocation: " + checkTime(relocation) + "ms.");
System.out.println("> Translation: " + checkTime(translation) + "ms.");
System.out.println("> Sampler: " + checkTime(samplerSampler) + "ms.");
}
System.out.println("#### Done.");
}
}

结果：

程序输出：

#### Validity checks...
Batch 1:
> Clipped: true.
> Relocation: true.
> Translation: true.
> Sampler: true.
Batch 2:
> Clipped: true.
> Relocation: true.
> Translation: true.
> Sampler: true.
Batch 3:
> Clipped: true.
> Relocation: true.
> Translation: true.
> Sampler: true.
#### Timings...
Batch 1:
> Clipped: 34668ms.
> Relocation: 22737ms.
> Translation: 5416ms.
> Sampler: 1152ms.
Batch 2:
> Clipped: 38521ms.
> Relocation: 22805ms.
> Translation: 5451ms.
> Sampler: 1156ms.
Batch 3:
> Clipped: 38275ms.
> Relocation: 22864ms.
> Translation: 5415ms.
> Sampler: 1163ms.
#### Done.

因此，对于一百万个样本，第一种方法大约需要37秒，第二种方法大约需要22秒，第三种方法大约需要5秒，最后一种方法恰好超过1秒(对于一百万个样本)。ComponentColorSampler在这些测试中最快的实现也是如此(每毫秒约865个样本)，并且可以在任何测试上运行Component。有效性检查只是为了稍微验证所采样的颜色是否具有正确的值。

注意 ：这些测试不是Swing /线程安全的，但是指出了正确使用它们(例如，在事件调度线程上执行采样)的性能。

2020-11-30