转载自http://www.cnitblog.com/zcy860511/archive/2009/01/25/54017.html
我将对java 2D进行一些讲述，当然是原创，不过也是参考自sun公司自己编写的java tutorial。
下面是这个指南的地址，以及一些来自官方的翻译版本
关于Composite的官方版本（英文）
AlphaComposite，是关于两个目标重叠的混合处理类，该类提供了一个getInstance的方法，其中的两个参数为rule和alpha，第二个参数将由调用者设置一个alpha值，即是透明度的设置，而第一个参数则是混合方式，也可以翻译为一种规则，并分为以下几种方式
SRC
SRC_IN
SRC_OUT
SRC_OVER
按照为都认识，所谓源模式，也就是将源(Source，以下简称src)放在上面，目标放在下面(Destination，以下简称dst)，in便是忽略掉src再dst的外面部分，out则是忽略掉里面部分，over则是覆盖在dst的上面
DST_IN
DST_OUT
DST_OVER
所谓目标模式，就是与源模式相反，将源模式放在下面，将目标模式放在上面，in便是忽略掉dst都与源的飞重叠部分，而out便是忽略掉dst的重叠部分，over自然是将dst覆盖在上面
CLEAR
顾名思义，就是清楚掉一部分。。。但是清楚的确实源部分，这个需要记忆一下
下面是sun提供的演示
这个是sun自己写的演示，所以比较具有权威性，我看过代码来，完全使用对象方式绘制，而问题就在于使用Graphics中的非对象方法时不能实现覆盖。
package com.ciash.test;
import java.awt.AlphaComposite;
import java.awt.Color;
import java.awt.Dimension;
import java.awt.Font;
import java.awt.Graphics;
import java.awt.Graphics2D;
import java.awt.GridBagConstraints;
import java.awt.GridBagLayout;
import java.awt.event.ItemEvent;
import java.awt.event.ItemListener;
import java.awt.event.WindowAdapter;
import java.awt.event.WindowEvent;
import java.awt.geom.Ellipse2D;
import java.awt.geom.Rectangle2D;
import java.awt.image.BufferedImage;
import javax.swing.JApplet;
import javax.swing.JComboBox;
import javax.swing.JFrame;
import javax.swing.JLabel;
import javax.swing.JPanel;
public class Composite extends JApplet implements ItemListener {
/**
* 字段描述:
*/
private static final long serialVersionUID = 1741029974281299482L;
CompPanel comp;
JLabel alphaLabel, rulesLabel;
JComboBox alphas, rules;
String alpha = "1.0";
int rule = 0;
// Initializes the layout of the components.
public void init() {
GridBagLayout layOut = new GridBagLayout();
getContentPane().setLayout(layOut);
GridBagConstraints l = new GridBagConstraints();
l.weightx = 1.0;
l.fill = GridBagConstraints.BOTH;
l.gridwidth = GridBagConstraints.RELATIVE;
alphaLabel = new JLabel();
alphaLabel.setText("Alphas");
Font newFont = getFont().deriveFont(1);
alphaLabel.setFont(newFont);
alphaLabel.setHorizontalAlignment(JLabel.CENTER);
layOut.setConstraints(alphaLabel, l);
getContentPane().add(alphaLabel);
GridBagConstraints c = new GridBagConstraints();
getContentPane().setLayout(layOut);
l.gridwidth = GridBagConstraints.REMAINDER;
rulesLabel = new JLabel();
rulesLabel.setText("Rules");
newFont = getFont().deriveFont(1);
rulesLabel.setFont(newFont);
rulesLabel.setHorizontalAlignment(JLabel.CENTER);
layOut.setConstraints(rulesLabel, l);
getContentPane().add(rulesLabel);
GridBagConstraints a = new GridBagConstraints();
a.gridwidth = GridBagConstraints.RELATIVE;
a.weightx = 1.0;
a.fill = GridBagConstraints.BOTH;
alphas = new JComboBox();
layOut.setConstraints(alphas, a);
alphas.addItem("1.0");
alphas.addItem("0.75");
alphas.addItem("0.50");
alphas.addItem("0.25");
alphas.addItem("0.0");
alphas.addItemListener(this);
getContentPane().add(alphas);
a.gridwidth = GridBagConstraints.REMAINDER;
rules = new JComboBox();
layOut.setConstraints(rules, a);
rules.addItem("SRC");
rules.addItem("DST_IN");
rules.addItem("DST_OUT");
rules.addItem("DST_OVER");
rules.addItem("SRC_IN");
rules.addItem("SRC_OVER");
rules.addItem("SRC_OUT");
rules.addItem("CLEAR");
rules.addItemListener(this);
getContentPane().add(rules);
GridBagConstraints fC = new GridBagConstraints();
fC.fill = GridBagConstraints.BOTH;
fC.weightx = 1.0;
fC.weighty = 1.0;
fC.gridwidth = GridBagConstraints.REMAINDER;
comp = new CompPanel();
layOut.setConstraints(comp, fC);
getContentPane().add(comp);
validate();
}
/*
* Detects a change in either of the Choice components. Resets the variable corresponding
* to the Choice whose state is changed. Invokes changeRule in CompPanel with the current
* alpha and composite rules.
*/
public void itemStateChanged(ItemEvent e){
if ( e.getStateChange() != ItemEvent.SELECTED ) {
return;
}
Object choice = e.getSource();
if ( choice == alphas ) {
alpha = (String)alphas.getSelectedItem();
} else {
rule = rules.getSelectedIndex();
}
comp.changeRule(alpha, rule);
}
public static void main(String s[]) {
JFrame f = new JFrame("Composite");
f.addWindowListener(new WindowAdapter() {
public void windowClosing(WindowEvent e) {System.exit(0);}
});
JApplet applet = new Composite();
f.getContentPane().add("Center", applet);
applet.init();
f.pack();
f.setSize(new Dimension(300,300));
f.setVisible(true);
}
}
class CompPanel extends JPanel {
AlphaComposite ac = AlphaComposite.getInstance(AlphaComposite.SRC);
float alpha = 1.0f;
public CompPanel(){}
// Resets the alpha and composite rules with selected items.
public void changeRule(String a, int rule) {
alpha = Float.valueOf(a).floatValue();
ac = AlphaComposite.getInstance(getRule(rule), alpha);
repaint();
}
// Gets the requested compositing rule.
public int getRule(int rule){
int alphaComp = 0;
switch ( rule ) {
case 0: alphaComp = AlphaComposite.SRC; break;
case 1: alphaComp = AlphaComposite.DST_IN; break;
case 2: alphaComp = AlphaComposite.DST_OUT; break;
case 3: alphaComp = AlphaComposite.DST_OVER; break;
case 4: alphaComp = AlphaComposite.SRC_IN; break;
case 5: alphaComp = AlphaComposite.SRC_OVER; break;
case 6: alphaComp = AlphaComposite.SRC_OUT; break;
case 7: alphaComp = AlphaComposite.CLEAR; break;
}
return alphaComp;
}
public void paintComponent(Graphics g) {
super.paintComponent( g );
Graphics2D g2 = (Graphics2D) g;
Dimension d = getSize();
int w = d.width;
int h = d.height;
// Creates the buffered image.
BufferedImage buffImg = new BufferedImage(w, h, BufferedImage.TYPE_INT_ARGB);
Graphics2D gbi = buffImg.createGraphics();
// Clears the previously drawn image.
g2.setColor(Color.white);
g2.fillRect(0, 0, d.width, d.height);
int rectx = w/4;
int recty = h/4;
// Draws the rectangle and ellipse into the buffered image.
gbi.setColor(new Color(0.0f, 0.0f, 1.0f, 1.0f));
gbi.fill(new Rectangle2D.Double(rectx, recty, 150, 100));
gbi.setColor(new Color(1.0f, 0.0f, 0.0f, 1.0f));
gbi.setComposite(ac);
gbi.fill(new Ellipse2D.Double(rectx+rectx/2,recty+recty/2,150,100));
// Draws the buffered image.
g2.drawImage(buffImg, null, 0, 0);
}
}
下面是实用方法
/**
* 图二的位置 从左上角开始
* @param x
* @param y
*/
public static void createPicTwo(int x,int y)
{
try
{
//读取第一张图片
File fileOne = new File("c:\\1.gif");
BufferedImage ImageOne = ImageIO.read(fileOne);
int width = ImageOne.getWidth();//图片宽度
int height = ImageOne.getHeight();//图片高度
//从图片中读取RGB
int[] ImageArrayOne = new int[width*height];
ImageArrayOne = ImageOne.getRGB(0,0,width,height,ImageArrayOne,0,width);
//对第二张图片做相同的处理
File fileTwo = new File("c:\\2.gif");
BufferedImage ImageTwo = ImageIO.read(fileTwo);
int widthTwo = ImageTwo.getWidth();//图片宽度
int heightTwo = ImageTwo.getHeight();//图片高度
int[] ImageArrayTwo = new int[widthTwo*heightTwo];
ImageArrayTwo =
ImageTwo.getRGB(0,0,widthTwo,heightTwo,ImageArrayTwo,0,widthTwo);
//生成新图片
BufferedImage ImageNew = new
BufferedImage(width*2,height,BufferedImage.TYPE_INT_RGB);
ImageNew.setRGB(0,0,width,height,ImageArrayOne,0,width);//设置左半部分的RGB
ImageNew.setRGB(x,y,widthTwo,heightTwo,ImageArrayTwo,0,widthTwo);//设置右半部分的RGB
File outFile = new File("c:\\out.png");
ImageIO.write(ImageNew, "png", outFile);//写图片
}
catch(Exception e)
{
e.printStackTrace();
}
}
/**
* 解决透明的问题
* @param filesrc
* @param logosrc
* @param outsrc
* @param x 位置
* @param y 位置
*/
public static void composePic(String filesrc,String logosrc,String outsrc,int x,int y) {
try {
File bgfile = new File(filesrc);
Image bg_src = javax.imageio.ImageIO.read(bgfile);
File logofile = new File(logosrc);
Image logo_src = javax.imageio.ImageIO.read(logofile);
int bg_width = bg_src.getWidth(null);
int bg_height = bg_src.getHeight(null);
int logo_width = logo_src.getWidth(null);;
int logo_height = logo_src.getHeight(null);
BufferedImage tag = new BufferedImage(bg_width, bg_height, BufferedImage.TYPE_INT_RGB);
Graphics2D g2d = tag.createGraphics();
g2d.drawImage(bg_src, 0, 0, bg_width, bg_height, null);
g2d.setComposite(AlphaComposite.getInstance(AlphaComposite.SRC_ATOP,1.0f)); //透明度设置开始
g2d.drawImage(logo_src,x,y,logo_width,logo_height, null);
g2d.setComposite(AlphaComposite.getInstance(AlphaComposite.SRC_OVER)); //透明度设置 结束
FileOutputStream out = new FileOutputStream(outsrc);
JPEGImageEncoder encoder = JPEGCodec.createJPEGEncoder(out);
encoder.encode(tag);
out.close();
}catch (Exception e) {
e.printStackTrace();
}
}调用main方法合成
public static void main(String[] args) {
Long star = System.currentTimeMillis();
composePic("E:\\a\\bb.png","E:\\a\\bc.png","E:\\a\\out_pic.png",59,218);
Long end =System.currentTimeMillis();
System.out.print("time====:"+(end-star));
}