Java -- AWT 画图，图像处理

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();
	}
}