AWT10-位图

1.概述

　　Graphics提供了drwaImage(Image image)来绘制位图，该方法需要一个位图做参数。

　　步骤：

　　　　1.创建Image的子类对象BufferedImage(int width,int height,int Image Type)，这相当于在内存生成了一张图片。

　　　　2.调用BufferedImage的getGraphics()方法获得画笔，此时即可在画布上绘图。

　　　　3.调用paint方法的drawImage方法，一次性的将BufferedImage绘制。

　　　　

import java.awt.*;
import java.awt.event.*;
import java.awt.image.BufferedImage;

public class PainterDemo {
    Frame frame = new Frame("简易手绘");

    private final int WIDTH = 500;
    private final int HEIGHT = 400;

    private int preX = -1;
    private int preY = -1;

    PopupMenu colorMenu = new PopupMenu();
    MenuItem blue = new MenuItem("蓝色");
    MenuItem red = new MenuItem("红色");
    MenuItem green = new MenuItem("绿色");

    private Color paintColor = Color.BLACK;

    BufferedImage bi = new BufferedImage(WIDTH, HEIGHT, BufferedImage.TYPE_INT_RGB);
    Graphics ig = bi.getGraphics();

    private class MyCanvas extends Canvas{
        @Override
        public void paint(Graphics g){
            g.drawImage(bi,0,0,null);
        }
    }

    MyCanvas canvas = new MyCanvas();


    public void init(){

        ActionListener ColorListener = new ActionListener() {
            @Override
            public void actionPerformed(ActionEvent e) {
                String command = e.getActionCommand();
                switch (command){
                    case "蓝色":
                        paintColor = Color.BLUE;
                        break;
                    case "红色":
                        paintColor = Color.RED;
                        break;
                    case "绿色":
                        paintColor = Color.GREEN;
                        break;
                }
            }
        };

        blue.addActionListener(ColorListener);
        red.addActionListener(ColorListener);
        green.addActionListener(ColorListener);

        colorMenu.add(blue);
        colorMenu.add(red);
        colorMenu.add(green);

        canvas.add(colorMenu);
        canvas.addMouseListener(new MouseAdapter() {
            @Override
            public void mouseReleased(MouseEvent e) {
                boolean trigger = e.isPopupTrigger();
                if (trigger){
                    colorMenu.show(canvas,e.getX(),e.getY());
                }

                preX = -1;
                preY = -1;
            }
        });

        ig.setColor(Color.white);
        ig.fillRect(0,0,WIDTH,HEIGHT);

        canvas.addMouseMotionListener(new MouseMotionAdapter() {
            @Override
            public void mouseDragged(MouseEvent e) {
                if (preX >= 0 && preY >= 0){
                    ig.setColor(paintColor);
                    ig.drawLine(preX,preY,e.getX(),e.getY());
                }

                preX=e.getX();
                preY=e.getY();

                canvas.repaint();
            }
        });

        canvas.setPreferredSize(new Dimension(WIDTH,HEIGHT));
        frame.add(canvas);
        
        frame.addWindowListener(new WindowAdapter() {
            @Override
            public void windowClosing(WindowEvent e) {
                System.exit(0);
            }
        });
        frame.pack();
        frame.setVisible(true);

    }
    public static void main(String[] args) {
        new PainterDemo().init();
    }
}

 2.ImageIO

　　实际生活中，有一种情况是程序打开本地的某张图进行编辑，编辑后重新保存在本地，这种情况要使用ImageIO。

方法名	说明
static BufferedImage read(File input)	读取本地图片
static BufferedImage read(inputStream input)	读取本地图片
static boolean write(renderedImage im,String formatName,File output)	在本地磁盘中输出图片

import javax.imageio.ImageIO;
import java.awt.*;
import java.awt.event.*;
import java.awt.image.BufferedImage;
import java.io.File;
import java.io.IOException;

public class PhotoViewDemo {
    Frame frame = new Frame("图片查看器");

    MenuBar menuBar = new MenuBar();
    Menu menu = new Menu("文件");
    MenuItem open = new MenuItem("打开",new MenuShortcut(KeyEvent.VK_O));
    MenuItem save = new MenuItem("保存",new MenuShortcut(KeyEvent.VK_S));

    BufferedImage image;

    private class MyCanvas extends Canvas{
        @Override
        public void paint(Graphics g){
            g.drawImage(image,0,0,null);
        }
    }

    MyCanvas canvas = new MyCanvas();

    public void init(){

        open.addActionListener(e ->{
            FileDialog fileDialog = new FileDialog(frame,"打开图片", FileDialog.LOAD);
            fileDialog.setVisible(true);
            String dir = fileDialog.getDirectory();
            String file = fileDialog.getFile();

            try {
                image = ImageIO.read(new File(dir,file));
                canvas.repaint();
            } catch (IOException ioException) {
                ioException.printStackTrace();
            }
        });

        save.addActionListener(e ->{
            FileDialog fileDialog = new FileDialog(frame,"保存图片", FileDialog.SAVE);
            fileDialog.setVisible(true);
            String dir = fileDialog.getDirectory();
            String file = fileDialog.getFile();

            try {
                ImageIO.write(image,"JPEG",new File(dir,file));
            } catch (IOException ioException) {
                ioException.printStackTrace();
            }
        });

        menu.add(open);
        menu.add(save);
        menuBar.add(menu);
        frame.setMenuBar(menuBar);
        frame.add(canvas);

        frame.pack();
        frame.setVisible(true);
        frame.addWindowListener(new WindowAdapter() {
            @Override
            public void windowClosing(WindowEvent e) {
                System.exit(0);
            }
        });
    }
    public static void main(String[] args) {
        new PhotoViewDemo().init();
    }
}