就像photoshop中缩小功能一样，将1280*1024的图片改成800*600！

测试成功。
添加包：
import com.sun.image.codec.jpeg.*;
import java.awt.image.BufferedImage;
import java.awt.image.Kernel;
import java.awt.image.BufferedImageOp;
import java.awt.image.*;
添加类成员:
private InputStream   inputStream;
private ByteArrayOutputStream bout;
private BufferedImage bufferedImage;


ImageIcon mi = new ImageIcon("E:\samples\java\SailiTest\T18Big.gif");
this.saveImage(mi.getImage(),"e:\2.jpg");//存成800*600的图像

//转换方法
public void saveImage(Image pImage,String ofileDirAndName)
{
  BufferedImage  bimg  =  null;
  int  w  =  pImage.getWidth(null);
  int  h  =  pImage.getHeight(null);
  int  []  pixels  =  new  int[w  *  h];
  PixelGrabber pg = new PixelGrabber(pImage,0, 0, w, h,pixels, 0, w);
  try {
   pg.grabPixels();
  }
  catch(InterruptedException e) {
  e.printStackTrace();
   }
   this.bout= new ByteArrayOutputStream();System.out.println("3");
   System.out.println("图像宽高:" +w+":"+h );
   BufferedImage bufferedImage= new BufferedImage(800,600,BufferedImage.TYPE_INT_RGB);

   bufferedImage.setRGB(0,0,800,600,pixels,0,w);
   float[] sharpKernel = { 0.0f, -1.0f, 0.0f,-1.0f, 5.0f, -1.0f, 0.0f, -1.0f, 0.0f };System.out.println("5");
   BufferedImageOp sharpen= new ConvolveOp( new Kernel(3, 3, sharpKernel), ConvolveOp.EDGE_NO_OP, null);
   BufferedImage sharp= sharpen.filter( bufferedImage, null );
   try
   {
    JPEGEncodeParam jpegParam= JPEGCodec.getDefaultJPEGEncodeParam( sharp );
    jpegParam.setQuality( 1.0f, false );
    JPEGImageEncoder jpeg= JPEGCodec.createJPEGEncoder( bout, jpegParam );
     jpeg.encode( bufferedImage );
     this.bout.writeTo(new FileOutputStream(ofileDirAndName));
  }
  catch(Exception ee)
  {
System.err.println("出错了"+ee);
   }
}