java 缩略图处理

import java.awt.Image;
import java.awt.image.BufferedImage;
import java.io.File;
import java.io.FileOutputStream;
import java.io.IOException;

import com.sun.image.codec.jpeg.JPEGCodec;
import com.sun.image.codec.jpeg.JPEGImageEncoder;

public class pic
{
    public static void main(String[] args) throws IOException
    {
        File file = new File("d:/temp/3.jpg"); 
        String newurl="d:/temp/4.jpg";  //新的缩略图保存地址
        Image src = javax.imageio.ImageIO.read(file);                     //构造Image对象
        float tagsize = 100;
        int old_w = src.getWidth(null);                                   //得到源图宽
        int old_h = src.getHeight(null);   
        int new_w = 0;
        int new_h = 0;                            //得到源图长
        int tempsize;
        float tempdouble; 
        if(old_w>old_h)
        {
            tempdouble=old_w/tagsize;
        }
        else
        {
            tempdouble=old_h/tagsize;
        }
        new_w = Math.round(old_w/tempdouble);
        new_h = Math.round(old_h/tempdouble);    //计算新图长宽
        BufferedImage tag = new BufferedImage(new_w,new_h,BufferedImage.TYPE_INT_RGB);
        tag.getGraphics().drawImage(src,0,0,new_w,new_h,null);             //绘制缩小后的图
        FileOutputStream newimage = new FileOutputStream(newurl);          //输出到文件流
        JPEGImageEncoder encoder  = JPEGCodec.createJPEGEncoder(newimage);
        encoder.encode(tag);                                               //近JPEG编码
        newimage.close();
    }
}