编辑：基于聊天中的长时间讨论，很明显有人
对意图有误解，而最初的问题
是XY问题：如何用遮罩
图像合成图像的问题仅是一个解决方案尝试的实际问题-
即画瓦片地图上的某些阴影/高光效果。该
帖子的原始版本可以在修订历史记录中看到。
显然，实际目标是在图像上添加“灯光效果”。这是
如何实现此目的的示例：
原始图像绘制在背景中
在图像上绘制“阴影图像”。
“阴影图像”最初是几乎不透明，几乎黑色的图像。灯光
用绘制成该图像RadialGradientPaint。
选择该涂料的颜色，以使它们
在应有灯光的地方使阴影图像不透明，并减少黑色。这会使这些区域看起来变
亮，而其他部分则保持黑暗。
import java.awt.AlphaComposite;import java.awt.Color;import java.awt.Graphics;import java.awt.Graphics2D;import java.awt.MultipleGradientPaint.CycleMethod;import java.awt.Point;import java.awt.RadialGradientPaint;import java.awt.event.MouseEvent;import java.awt.event.MouseMotionListener;import java.awt.geom.Point2D;import java.awt.image.BufferedImage;import java.util.Random;import javax.swing.Jframe;import javax.swing.JPanel;import javax.swing.SwingUtilities;public class LightEffectTest2{ public static void main(String args[]) { SwingUtilities.invokeLater(new Runnable() { public void run() { new LightEffectTest2(); } }); } public LightEffectTest2() { Jframe f = new Jframe(); f.setDefaultCloseOperation(Jframe.EXIT_ON_CLOSE); f.getContentPane().add(new LightEffectPanel2()); f.setSize(600,600); f.setVisible(true); }}class LightEffectPanel2 extends JPanel implements MouseMotionListener{ private Point point = new Point(0,0); private BufferedImage image; private BufferedImage shadow; public LightEffectPanel2() { image = createExampleImage(600,600); shadow = new BufferedImage(image.getWidth(), image.getHeight(), BufferedImage.TYPE_INT_ARGB); addMouseMotionListener(this); } private static BufferedImage createExampleImage(int w, int h) { BufferedImage image = new BufferedImage(w, h, BufferedImage.TYPE_INT_ARGB); Graphics g = image.getGraphics(); Random random = new Random(0); for (int i=0; i<200; i++) { int x = random.nextInt(w); int y = random.nextInt(h); Color c = new Color( random.nextInt(255), random.nextInt(255), random.nextInt(255)); g.setColor(c); g.fillOval(x-20, y-20, 40, 40); } g.dispose(); return image; } @Override protected void paintComponent(Graphics gr) { super.paintComponent(gr); Graphics2D g = (Graphics2D)gr; g.drawImage(image, 0,0,null); drawLights(); g.drawImage(shadow, 0,0, null); } private void drawLights() { Graphics2D g = shadow.createGraphics(); g.setComposite(AlphaComposite.Src); g.setColor(new Color(0,0,16,240)); g.fillRect(0,0,getWidth(),getHeight()); drawLight(g, new Point(100,100)); drawLight(g, point); g.dispose(); } private void drawLight(Graphics2D g, Point pt) { float radius = 100; g.setComposite(AlphaComposite.DstOut); Point2D center = new Point2D.Float(pt.x, pt.y); float[] dist = {0.0f, 1.0f}; Color[] colors = {new Color(255,255,255,255), new Color(0,0,0,0) }; RadialGradientPaint p = new RadialGradientPaint( center, radius, dist, colors, CycleMethod.NO_CYCLE); g.setPaint(p); g.fillOval(pt.x-(int)radius,pt.y-(int)radius,(int)radius*2,(int)radius*2); } @Override public void mouseDragged(MouseEvent e) { } @Override public void mouseMoved(MouseEvent e) { point = e.getPoint(); repaint(); }}（后）编辑对于注释中的请求：
要添加另一个阴影（与现有的灯光无关），可以创建一种
drawShadow在
绘制灯光之后重新应用阴影的方法。它基本上使用了另一个RadialGradientPaint部分
“还原”原始不透明暗影图像的图像。
（此处阴影被赋予了较清晰的边框，以使效果更
明显）
import java.awt.AlphaComposite;import java.awt.Color;import java.awt.Graphics;import java.awt.Graphics2D;import java.awt.MultipleGradientPaint.CycleMethod;import java.awt.Point;import java.awt.RadialGradientPaint;import java.awt.event.MouseEvent;import java.awt.event.MouseMotionListener;import java.awt.geom.Point2D;import java.awt.image.BufferedImage;import java.util.Random;import javax.swing.Jframe;import javax.swing.JPanel;import javax.swing.SwingUtilities;public class LightEffectTest3{ public static void main(String args[]) { SwingUtilities.invokeLater(new Runnable() { public void run() { new LightEffectTest3(); } }); } public LightEffectTest3() { Jframe f = new Jframe(); f.setDefaultCloseOperation(Jframe.EXIT_ON_CLOSE); f.getContentPane().add(new LightEffectPanel3()); f.setSize(600,600); f.setVisible(true); }}class LightEffectPanel3 extends JPanel implements MouseMotionListener{ private Point point = new Point(0,0); private BufferedImage image; private BufferedImage shadow; public LightEffectPanel3() { image = createExampleImage(600,600); shadow = new BufferedImage(image.getWidth(), image.getHeight(), BufferedImage.TYPE_INT_ARGB); addMouseMotionListener(this); } private static BufferedImage createExampleImage(int w, int h) { BufferedImage image = new BufferedImage(w, h, BufferedImage.TYPE_INT_ARGB); Graphics g = image.getGraphics(); Random random = new Random(0); for (int i=0; i<200; i++) { int x = random.nextInt(w); int y = random.nextInt(h); Color c = new Color( random.nextInt(255), random.nextInt(255), random.nextInt(255)); g.setColor(c); g.fillOval(x-20, y-20, 40, 40); } g.dispose(); return image; } @Override protected void paintComponent(Graphics gr) { super.paintComponent(gr); Graphics2D g = (Graphics2D)gr; g.drawImage(image, 0,0,null); drawLights(); g.drawImage(shadow, 0,0, null); } private void drawLights() { Graphics2D g = shadow.createGraphics(); g.setComposite(AlphaComposite.Src); g.setColor(new Color(0,0,16,240)); g.fillRect(0,0,getWidth(),getHeight()); drawLight(g, new Point(200,200)); drawLight(g, point); drawShadow(g, new Point(250,250)); g.dispose(); } private void drawLight(Graphics2D g, Point pt) { float radius = 150; g.setComposite(AlphaComposite.DstOut); Point2D center = new Point2D.Float(pt.x, pt.y); float[] dist = {0.0f, 1.0f}; Color[] colors = {new Color(255,255,255,255), new Color(0,0,0,0) }; RadialGradientPaint p = new RadialGradientPaint( center, radius, dist, colors, CycleMethod.NO_CYCLE); g.setPaint(p); g.fillOval(pt.x-(int)radius,pt.y-(int)radius, (int)radius*2,(int)radius*2); } private void drawShadow(Graphics2D g, Point pt) { float radius = 75; g.setComposite(AlphaComposite.DstOver); Point2D center = new Point2D.Float(pt.x, pt.y); float[] dist = {0.0f, 0.7f, 1.0f}; Color[] colors = { new Color(0,0,0,200), new Color(0,0,0,150), new Color(255,255,255,0) }; RadialGradientPaint p = new RadialGradientPaint( center, radius, dist, colors, CycleMethod.NO_CYCLE); g.setPaint(p); g.fillOval(pt.x-(int)radius,pt.y-(int)radius, (int)radius*2,(int)radius*2); } @Override public void mouseDragged(MouseEvent e) { } @Override public void mouseMoved(MouseEvent e) { point = e.getPoint(); repaint(); }}
