1. AWT画图 Graphics类 提供绘制简单图形的方法
更新图片时用到 repaint , update , 程序不应该主动调用paint和update， 这两个方法都应该是由AWT系统负责调用，用户重写paint 即可。
示例：
public class Main {
private final String RECT_SHAPE = "rect";
private final String OVAL_SHAPE = "oval";
private Frame f = new Frame();
private Button rect = new Button("Rect");
private Button oval = new Button("Oval");
private String shape = "";
private MyCanvas drawArea = new MyCanvas();
void init()
{
Panel p = new Panel();
p.add(rect);
p.add(oval);
rect.addActionListener(new ActionListener() {
@Override
public void actionPerformed(ActionEvent e) {
// TODO Auto-generated method stub
shape = RECT_SHAPE;
drawArea.repaint(); //重画， 会调用paint方法。。。
}
});
oval.addActionListener(new ActionListener() {
@Override
public void actionPerformed(ActionEvent e) {
// TODO Auto-generated method stub
shape = OVAL_SHAPE;
drawArea.repaint();
}
});
f.addWindowListener(new WindowAdapter() {
public void windowClosing(WindowEvent e)
{
System.exit(0);
}
});
drawArea.setPreferredSize(new Dimension(250, 180));
f.add(drawArea);
f.add(p, BorderLayout.SOUTH);
f.pack();
f.setVisible(true);
}
public static void main(String[] args) {
new Main().init();
}
class MyCanvas extends Canvas // 画布
{
public void paint(Graphics g) //重写paint方法
{
Random rand = new Random();
if(shape.equals(RECT_SHAPE))
{
g.setColor(new Color(220, 100, 80));
g.drawRect(rand.nextInt(200), rand.nextInt(120), 40, 60);
}
if(shape.equals(OVAL_SHAPE))
{
g.setColor(new Color(80, 100, 200));
g.fillOval(rand.nextInt(200), rand.nextInt(120), 50, 40);
}
}
}
}2. 使用image类 BufferedImage 类处理位图
画板：
import java.awt.Canvas;
import java.awt.Color;
import java.awt.Dimension;
import java.awt.Frame;
import java.awt.Graphics;
import java.awt.MenuItem;
import java.awt.PopupMenu;
import java.awt.event.ActionEvent;
import java.awt.event.ActionListener;
import java.awt.event.MouseAdapter;
import java.awt.event.MouseEvent;
import java.awt.event.MouseMotionAdapter;
import java.awt.event.MouseMotionListener;
import java.awt.event.WindowAdapter;
import java.awt.event.WindowEvent;
import java.awt.image.BufferedImage; public class HandDraw { /**
* @param args
*/
//画区大小
private final int AREA_WIDTH = 500;
private final int AREA_HEIGHT = 400;
//鼠标坐标
private int preX = -1;
private int preY = -1;
//右键惨淡
PopupMenu pop = new PopupMenu();
MenuItem redItem = new MenuItem("Red");
MenuItem greenItem = new MenuItem("Green");
MenuItem blueItem = new MenuItem("Blue");
//Bufferedimage 对象
BufferedImage image = new BufferedImage(AREA_WIDTH, AREA_HEIGHT,
BufferedImage.TYPE_INT_RGB);
Graphics g = image.getGraphics();
private Frame f= new Frame("HandDraw");
private String shape = "";
private Color foreColor = new Color(255, 0, 0);
private DrawCanvas drawArea = new DrawCanvas(); public void init()
{
ActionListener menuListener = new ActionListener() {
@Override
public void actionPerformed(ActionEvent e) {
// TODO Auto-generated method stub
if( e.getActionCommand().equals("Green") )
{
foreColor = new Color(0, 255, 0);
System.out.println("Green");
}
else if( e.getActionCommand().equals("Red") )
{
foreColor = new Color(255, 0, 0);
System.out.println("Red");
}
else if( e.getActionCommand().equals("Blue") )
{
foreColor = new Color(0, 0, 255);
System.out.println("Blue");
}
}
};
redItem.addActionListener(menuListener);
greenItem.addActionListener(menuListener);
blueItem.addActionListener(menuListener);
pop.add(redItem);
pop.add(greenItem);
pop.add(blueItem);
drawArea.add(pop);
drawArea.addMouseListener(new MouseAdapter() {
public void mouseReleased(MouseEvent e)
{
if(e.isPopupTrigger())
{
pop.show(drawArea, e.getX(), e.getY());
}
preX = -1;
preY = -1;
}
}); g.fillRect(0, 0, AREA_WIDTH, AREA_HEIGHT);
drawArea.setPreferredSize(new Dimension(AREA_WIDTH, AREA_HEIGHT));
drawArea.addMouseMotionListener(new MouseMotionAdapter() {
public void mouseDragged(MouseEvent e)
{
if( preX > 0 && preY > 0 )
{
g.setColor(foreColor);
g.drawLine(preX, preY, e.getX(), e.getY());
}
preX = e.getX();
preY = e.getY();
drawArea.repaint();
}
}); f.addWindowListener(new WindowAdapter() {
public void windowClosing(WindowEvent w)
{
System.exit(0);
}
});
f.add(drawArea);
f.pack();
f.setVisible(true); } public static void main(String[] args) {
// TODO Auto-generated method stub
new HandDraw().init();
} class DrawCanvas extends Canvas
{
public void paint(Graphics g)
{
g.drawImage(image, 0, 0, null);
}
} }
3. 使用ImageIO 输入 输出位图
ImageIO有静态方法 getReaderFormatNames() 等获取 支持的读入写入的图片格式。
public class Main {
private final int WIDTH = 800;
private final int HEIGHT = 600;
BufferedImage image = new BufferedImage(WIDTH, HEIGHT, BufferedImage.TYPE_INT_RGB );
Graphics g= image.getGraphics();
public void zoom() throws IOException
{
Image srcImage = ImageIO.read(new File("/home/test/test.png")); //读取图片文件
g.drawImage(srcImage, 0, 0, WIDTH, HEIGHT, null); //将原始图片 按固定大小绘制到image中
ImageIO.write(image, "jpeg", new File("/home/test/testCopy.jpg")); //写入磁盘
}
public static void main(String[] args) throws IOException {
// TODO Auto-generated method stub
new Main().zoom();
}
}