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swing 使用Graphic2D 绘制图片，要实现对图片进行缩放和自由拖动。
1.以鼠标所在的位置为中心，滚轮控制缩放
2.缩放后再支持鼠标拖动。
基本原理：
利用scale() 函数。进行缩放。但是要注意的地方是，如果是在 public void paintComponent(Graphics g) 里面通过这个Graphics g 参数获取graphic对象进行绘制，scale不会影响下一次的绘制。
一：所以，我们可以自行创建一个 “绘图区”， 创建一个空的ImageBuffer, 然后获取这个ImageBuffer的 Graphics, 后续全部往这个ImageBuffer的 Graphics 绘制.
二： 最后在frame的paintComponent把我们这个 绘图区原样展示出来即可。 即，frame的paintComponent只是固定将 绘图区作为一个图片绘制。
三：甚至可以创建多个ImageBuffer ，实现类似于ps多图层的样子，各个图层独立，paitComponent 汇总显示图层。
自己创建的ImageBuffer的 Graphics ，每次scale都是以上一次作为基础，累计的缩放。
利用transrate进行移动，（移动的是坐标系）。 每次transrate都是以上一次作为基础，累计的平移。
来实现我们的关键代码：
作为demo, 代码尽量是一个 main（）到底：
swingDemo.java
import java.awt.Color;
import java.awt.Dimension;
import java.awt.Graphics;
import java.awt.Graphics2D;
import java.awt.Point;
import java.awt.RenderingHints;
import java.awt.event.ActionEvent;
import java.awt.event.ActionListener;
import java.awt.event.MouseAdapter;
import java.awt.event.MouseEvent;
import java.awt.event.MouseListener;
import java.awt.event.MouseWheelEvent;
import java.awt.event.MouseWheelListener;
import java.awt.geom.AffineTransform;
import java.awt.image.BufferedImage;
import java.io.File;
import java.io.IOException;import javax.imageio.ImageIO;
import javax.swing.JFileChooser;
import javax.swing.JFrame;
import javax.swing.JMenu;
import javax.swing.JMenuBar;
import javax.swing.JMenuItem;
import javax.swing.JPanel;public class swingDemo {public static void main(String args[]) {new swingDemo();}public static Color BG_COLOR = new Color(128, 128, 128);public swingDemo() {JFrame mjf = new JFrame("图片查看");ImagePanle mImgeView = new ImagePanle();mImgeView.setPreferredSize(new Dimension(500, 500));mImgeView.setMinimumSize(new Dimension(500, 500));mImgeView.setBackground(BG_COLOR);JMenuBar jmb = new JMenuBar();JMenu meSetting = new JMenu("文件");JMenuItem mOpen = new JMenuItem("打开");mOpen.addActionListener(new ActionListener() {@Overridepublic void actionPerformed(ActionEvent e) {// TODO Auto-generated method stubBufferedImage curBufferedImg;JFileChooser fileChooser = new JFileChooser();fileChooser.setMultiSelectionEnabled(true);fileChooser.setFileSelectionMode(JFileChooser.FILES_ONLY);fileChooser.setMultiSelectionEnabled(false);int option = fileChooser.showOpenDialog(mjf);if (option == JFileChooser.APPROVE_OPTION) {try {File file = fileChooser.getSelectedFile();curBufferedImg = ImageIO.read(new File(file.getAbsolutePath()));mImgeView.updateImage(curBufferedImg);} catch (IOException e1) {// TODO Auto-generated catch blocke1.printStackTrace();}}}});meSetting.add(mOpen);jmb.add(meSetting);mjf.setJMenuBar(jmb);mjf.add(mImgeView);mjf.setMinimumSize(new Dimension(800, 600));mjf.setVisible(true);mjf.setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);}class ImagePanle extends JPanel {BufferedImage mSrcBuffeImg = null;private static final long serialVersionUID = 1L;private double mScale = 1.0;private static final boolean B_REAL_SIZE = true;private double mCurX = 0;private double mCurY = 0;private double mStartX = 0;private double mStartY = 0;private double mTranslateX = 0;private double mTranslateY = 0;// 记录最初原始坐标系，用于清除背景AffineTransform mOriginTransform;BufferedImage mViewBufferImg;Graphics2D mViewG2d;void refreshView() {clear_buffer(mViewG2d, mOriginTransform, mViewBufferImg);mViewG2d.drawImage(mSrcBuffeImg, 0, 0, null);repaint();}void clear_buffer(Graphics2D g2d, AffineTransform org, BufferedImage bufImg) {
// 将保存的测量数据，重新在经过变换后的坐标系上进行绘制// 先恢复一下原始状态，保证清空的坐标是全部，执行清空，然后再切会来AffineTransform temp = g2d.getTransform();g2d.setTransform(org);g2d.clearRect(0, 0, bufImg.getWidth(), bufImg.getHeight());g2d.setTransform(temp);}public void updateImage(BufferedImage srcImage) {mSrcBuffeImg = srcImage;mViewBufferImg = new BufferedImage(this.getWidth(), this.getHeight(), BufferedImage.TYPE_INT_ARGB);System.out.println("create buff image");mViewG2d = mViewBufferImg.createGraphics();mViewG2d.setRenderingHint(RenderingHints.KEY_ANTIALIASING, RenderingHints.VALUE_ANTIALIAS_ON);mViewG2d.setBackground(BG_COLOR);System.out.println("crate bufg2d");mOriginTransform = mViewG2d.getTransform();refreshView();}private Point internal_getImagePoint(double mouseX, double mouseY) {// 不管是先平移后缩放还是先缩放后平移，都以 先减 再缩放的方式可以获取正确double rawTranslateX = mViewG2d.getTransform().getTranslateX();double rawTranslateY = mViewG2d.getTransform().getTranslateY();// 获取当前的 Scale Transformdouble scaleX = mViewG2d.getTransform().getScaleX();double scaleY = mViewG2d.getTransform().getScaleY();// 不管是先平移后缩放还是先缩放后平移，都以 先减 再缩放的方式可以获取正确int imageX = (int) ((mouseX - rawTranslateX) / scaleX);int imageY = (int) ((mouseY - rawTranslateY) / scaleY);return new Point(imageX, imageY);}public ImagePanle() {// 启用双缓存setDoubleBuffered(true);this.addMouseWheelListener((MouseWheelListener) new MouseWheelListener() {@Overridepublic void mouseWheelMoved(MouseWheelEvent e) {if (mViewG2d == null) {return;}mCurX = e.getX();mCurY = e.getY();int notches = e.getWheelRotation();if (notches < 0) {// 滚轮向上，放大画布mScale = 1.1;} else {// 滚轮向下，缩小画布mScale = 0.9;}Point imagePoint = internal_getImagePoint(e.getX(), e.getY());int imageX = imagePoint.x;int imageY = imagePoint.y;System.out.println("x:" + e.getX() + "y:" + e.getY() + ",imagex:" + imageX + "x" + imageY);double tralateX = mScale * imageX - imageX;double tralateY = mScale * imageY - imageY;mViewG2d.scale(mScale, mScale);mViewG2d.translate(-tralateX / mScale, -tralateY / mScale); // 图片方大，就需要把坐标往左移动，移动的尺度是要考虑缩放的// 先恢复一下原始状态，保证清空的坐标是全部，执行清空，然后再切会来AffineTransform temp = mViewG2d.getTransform();mViewG2d.setTransform(mOriginTransform);mViewG2d.clearRect(0, 0, mViewBufferImg.getWidth(), mViewBufferImg.getHeight());mViewG2d.setTransform(temp);mViewG2d.drawImage(mSrcBuffeImg, 0, 0, null);repaint(); // 重新绘制画布}});this.addMouseListener(new MouseListener() {@Overridepublic void mouseReleased(MouseEvent e) {// TODO Auto-generated method stubSystem.out.println("mouseReleased:" + e.getX() + "x" + e.getY());}@Overridepublic void mousePressed(MouseEvent e) {// TODO Auto-generated method stubSystem.out.println("mousePressed----:" + e.getX() + "x" + e.getY());mStartX = e.getX();mStartY = e.getY();}@Overridepublic void mouseExited(MouseEvent e) {// TODO Auto-generated method stub}@Overridepublic void mouseEntered(MouseEvent e) {// TODO Auto-generated method stub}@Overridepublic void mouseClicked(MouseEvent e) {// TODO Auto-generated method stubSystem.out.println("mouseClicked----:" + e.getX() + "x" + e.getY());}});this.addMouseMotionListener(new MouseAdapter() {@Overridepublic void mouseMoved(MouseEvent e) {// TODO Auto-generated method stub}@Overridepublic void mouseDragged(MouseEvent e) {// TODO Auto-generated method stubif (mViewG2d == null) {return;}mCurX = e.getX();mCurY = e.getY();System.out.println("mouseDragged:" + e.getX() + "x" + e.getY() + "trans:" + (mCurX - mStartX) + ":"+ (mCurY - mStartY));// 平移坐标，也是相对于变换后的坐标系而言的，所以double scaleX = mViewG2d.getTransform().getScaleX();double scaleY = mViewG2d.getTransform().getScaleY();// TODO mCurX - mStartX 太小，比如为2， 而scalX 比较大，比如为3 则移动的时候回发生 (int)2/3 ==0; 不移动。// 解决方案，把移动 ，全部在原始坐标系上做，也就是最后绘制缓冲区的时候，drawimage(transX,transY)mTranslateX = (mCurX - mStartX) / scaleX;mTranslateY = (mCurY - mStartY) / scaleY;// 自身就是累计的mViewG2d.translate(mTranslateX, mTranslateY);mStartX = mCurX;mStartY = mCurY;System.out.println("mouseDragged: over+++");// 先恢复一下原始状态，保证清空的坐标是全部，执行清空，然后再切会来AffineTransform temp = mViewG2d.getTransform();mViewG2d.setTransform(mOriginTransform);mViewG2d.clearRect(0, 0, mViewBufferImg.getWidth(), mViewBufferImg.getHeight());mViewG2d.setTransform(temp);mViewG2d.drawImage(mSrcBuffeImg, 0, 0, null);repaint();}});}public void reset_scale() {
// 恢复到1.0 缩放，0,0 左上角对齐mCurX = 0;mCurY = 0;mScale = 1.0;mViewG2d.setTransform(mOriginTransform);mViewG2d.clearRect(0, 0, mViewBufferImg.getWidth(), mViewBufferImg.getHeight());mViewG2d.drawImage(mSrcBuffeImg, 0, 0, null);repaint(); // 重新绘制画布}@Overridepublic void paintComponent(Graphics g) {super.paintComponent(g);if (mViewBufferImg == null) {return;}
// 如果有多个“图层”要注意图层的顺序Graphics2D g2d = ((Graphics2D) g);g2d.drawImage(mViewBufferImg, 0, 0, null);System.out.println("draw-----------:" + getWidth() + "x" + getHeight());}}}