图片的缩放

import java.awt.BorderLayout; import java.awt.Color; import java.awt.Dimension; import java.awt.Graphics; import java.awt.Graphics2D; import java.awt.event.MouseWheelEvent; import java.awt.event.MouseWheelListener; import java.awt.event.WindowAdapter; import java.awt.event.WindowEvent; 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.JFrame; import javax.swing.JPanel;

public class ImageSuoFang extends JFrame {    /**   *   */  private static final long serialVersionUID = 1L;  DrawResImg dri;  BorderLayout bl;    public ImageSuoFang() {   dri = new DrawResImg("D://1.png");   bl = new BorderLayout();   setMinimumSize(new Dimension(1000, 800));   setLayout(bl);   add(dri, bl.CENTER);      addWindowListener(new WindowAdapter() {    public void windowClosing(WindowEvent e) {     System.exit(0);    }   });   setVisible(true);  }    class DrawResImg extends JPanel implements MouseWheelListener{      /**    *    */   private static final long serialVersionUID = 1L;   BufferedImage resBI;   BufferedImage resBI2;   int count = 0;      public DrawResImg(String path) {    try {     resBI = ImageIO.read(new File(path));    } catch (IOException e) {     e.printStackTrace();    }    resBI2 = resBI;    addMouseWheelListener(this);   }      public void paint(Graphics g) {    g.setColor(Color.WHITE);    g.fillRect(0, 0, getWidth(), getHeight());    g.drawImage(resBI2, 200, 100, this);   }

  public void mouseWheelMoved(MouseWheelEvent e) {    if (e.getWheelRotation() < 0) {     count--;    }    if (e.getWheelRotation() > 0) {     count++;    }        resBI2 = resizePic(resBI, resBI.getWidth() + (10 * count), resBI.getHeight() + (10 * count));                repaint();   }     }    private static BufferedImage resizePic(BufferedImage source, int targetW,                int targetH) {            // targetW，targetH分别表示目标长和宽            int type = source.getType();            BufferedImage target = null;            double sx = (double) targetW / source.getWidth();            double sy = (double) targetH / source.getHeight();            // 这里想实现在targetW，targetH范围内实现等比缩放。如果不需要等比缩放            // 则将下面的if else语句注释即可            if (sx < sy) {                sx = sy;                targetW = (int) (sx * source.getWidth());            } else {                sy = sx;                targetH = (int) (sy * source.getHeight());            }            target = new BufferedImage(targetW, targetH, type);            Graphics2D g = target.createGraphics();            // smoother than exlax:            /*g.setRenderingHint(RenderingHints.KEY_INTERPOLATION,                    RenderingHints.VALUE_INTERPOLATION_BICUBIC);   */         g.drawRenderedImage(source, AffineTransform.getScaleInstance(sx, sy));            //g.dispose();            return target;        }   

   public static void main(String[] arg){   new ImageSuoFang();  }

  }