我想在另一个上面绘制一个部分透明的图像（在物体上制作阴影）。我目前正在使用java的Graphics2D类进行渲染，我被告知将复合设置为AlphaComposite，但这只是将它设置为完全透明。
我可以使用当前设置执行此操作吗？我该怎么做才能解决这个问题？
这是我被告知会使其部分透明的代码：
AlphaComposite ac = java.awt.AlphaComposite.getInstance(AlphaComposite.CLEAR, 0.5F);
g.setComposite(ac);
（我顺便使用png图像）
继承你的sscce（这些都是在不同的类中，但为了简单起见我把它们放在一起）（我使用一个名为＆＃34的图像;测试＆＃34;在本地文件夹＆＃34;图像＆＃34;，你可以只要它是一个名为相同的png图像
，就可以使用任何东西import java.awt.AlphaComposite;
import java.awt.Color;
import java.awt.DisplayMode;
import java.awt.Font;
import java.awt.Graphics2D;
import java.awt.Window;
import javax.swing.ImageIcon;
import com.blazingkin.atrox.ScreenManager;
public class AtroxAdventrum{
public static void main(String[] args) {
new AtroxAdventrum().run();
}
private static DisplayMode modes[] = {
//new DisplayMode(1080,720,32,0),
//new DisplayMode(1080,720,24,0),
//new DisplayMode(1080,720,16,0),
//new DisplayMode(1440,900,32,0),
//new DisplayMode(1440,900,24,0),
//new DisplayMode(1440,900,16,0),
};
private boolean running = true;
public ScreenManager s;
public void stop(){
running = false;
}
public void run(){
try{
init();
gameLoop();
}finally{
s.restoreScreen();
}
}
public void init(){
s = new ScreenManager();
DisplayMode dm = s.findFirstCompatibleMode(modes);
s.setFullScreen(dm);
Window w = s.getFullScreenWindow();
w.setFont(new Font("Arial", Font.PLAIN, 20));
w.setBackground(Color.black);
w.setForeground(Color.white);
}
public void gameLoop(){
long startTime = System.currentTimeMillis();
long cumTime = startTime;
while (running)
{
long timePassed = System.currentTimeMillis() - cumTime;
cumTime += timePassed;
if (limitfps){
try{
Thread.sleep(15);
}catch(Exception e){}
}
update(timePassed);
Graphics2D g = s.getGraphics();
draw(g);
g.dispose();
s.update();
}
}
public void update(long timePassed){
}
public boolean limitfps = false;
public void draw(Graphics2D g){
g.clearRect(0, 0, s.getWidth(), s.getHeight());
AlphaComposite ac = java.awt.AlphaComposite.getInstance(AlphaComposite.CLEAR,0.5F);
g.setComposite(ac);
g.drawImage(new ImageIcon("Images/Test.png").getImage(), 30, 30, 30, 30, null);
}
}
如果您运行此操作，则必须使用alt + tab并结束该过程（因为它在此部分代码中没有任何内容可以执行此操作）
答案 0 :(得分：21)
您使用了错误的规则 - 请勿使用AlphaComposite.CLEAR。
AlphaComposite API说明了CLEAR：
目的地的颜色和阿尔法都被清除（Porter-Duff清除规则）。源和目的地都不用作输入。
这样会使图像消失。试验其他规则。当你创建你的SSCCE时，我创建了我的。看看当你为另一个注释掉一个规则行时会发生什么。例如，改变这个
// int rule = AlphaComposite.CLEAR;
int rule = AlphaComposite.SRC_OVER;
到此：
int rule = AlphaComposite.CLEAR;
// int rule = AlphaComposite.SRC_OVER;
整个SSCCE：
import java.awt.AlphaComposite;
import java.awt.BasicStroke;
import java.awt.Color;
import java.awt.Composite;
import java.awt.Dimension;
import java.awt.Graphics;
import java.awt.Graphics2D;
import java.awt.RenderingHints;
import java.awt.Stroke;
import java.awt.image.BufferedImage;
import javax.swing.*;
public class TestAlphaComposite extends JPanel {
private static final int PREF_W = 400;
private static final int PREF_H = PREF_W;
private static final Stroke BASIC_STROKE = new BasicStroke(6f);
BufferedImage backgroundImage;
BufferedImage overlayImage;
public TestAlphaComposite() {
backgroundImage = createBackGroundImage();
overlayImage = createOverlayImage();
}
private BufferedImage createBackGroundImage() {
BufferedImage img = new BufferedImage(PREF_W, PREF_H,
BufferedImage.TYPE_INT_ARGB);
Graphics2D g2 = img.createGraphics();
g2.setRenderingHint(RenderingHints.KEY_ANTIALIASING,
RenderingHints.VALUE_ANTIALIAS_ON);
g2.setStroke(BASIC_STROKE);
g2.setColor(Color.blue);
int circleCount = 10;
for (int i = 0; i < circleCount ; i++) {
int x = (i * PREF_W) / (2 * circleCount);
int y = x;
int w = PREF_W - 2 * x;
int h = w;
g2.drawOval(x, y, w, h);
}
g2.dispose();
return img;
}
private BufferedImage createOverlayImage() {
BufferedImage img = new BufferedImage(PREF_W, PREF_H,
BufferedImage.TYPE_INT_ARGB);
Graphics2D g2 = img.createGraphics();
g2.setRenderingHint(RenderingHints.KEY_ANTIALIASING,
RenderingHints.VALUE_ANTIALIAS_ON);
g2.setStroke(BASIC_STROKE);
g2.setColor(Color.red);
int circleCount = 10;
for (int i = 0; i < circleCount + 1; i++) {
int x1 = (i * PREF_W) / (circleCount);
int y1 = 0;
int x2 = PREF_W - x1;
int y2 = PREF_H;
float alpha = (float)i / circleCount;
if (alpha > 1f) {
alpha = 1f;
}
// int rule = AlphaComposite.CLEAR;
int rule = AlphaComposite.SRC_OVER;
Composite comp = AlphaComposite.getInstance(rule , alpha );
g2.setComposite(comp );
g2.drawLine(x1, y1, x2, y2);
}
g2.dispose();
return img;
}
@Override
public Dimension getPreferredSize() {
return new Dimension(PREF_W, PREF_H);
}
@Override
protected void paintComponent(Graphics g) {
super.paintComponent(g);
if (backgroundImage != null) {
g.drawImage(backgroundImage, 0, 0, null);
}
if (overlayImage != null) {
g.drawImage(overlayImage, 0, 0, null);
}
}
private static void createAndShowGui() {
JFrame frame = new JFrame("TestAlphaComposite");
frame.setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);
frame.getContentPane().add(new TestAlphaComposite());
frame.pack();
frame.setLocationRelativeTo(null);
frame.setVisible(true);
}
public static void main(String[] args) {
SwingUtilities.invokeLater(new Runnable() {
public void run() {
createAndShowGui();
}
});
}
}
顺便说一下，你的SSCCE并不是真正的SSCCE。我们任何人都无法编译或运行该代码，因为它具有我们无法访问的依赖关系，即＆＃34; com.blazingkin.atrox.ScreenManager＆＃34;。如果您将来需要我们的帮助，您将要写出更好的符合sscce的要求。