java 缩略图

package test;
import java.awt.Image;
import java.awt.image.BufferedImage;
import java.io.File;
import java.io.FileOutputStream;
import javax.imageio.ImageIO;
import com.sun.image.codec.jpeg.JPEGCodec;
import com.sun.image.codec.jpeg.JPEGImageEncoder;

public class ImageUtil {
    
    public static void main(String[] args) {
        File file = new File("D:/image.JPG");
        try {
            makeSmallImage(file, "d:/image1.jpg");
        } catch (Exception e) {
            e.printStackTrace();
        }
    }
    /**
     * 生成缩略图
     * @param srcImageFile 源图片文件的File实例      File file = new File("文件名");
     * @param dstImageFileName 待生成的缩略图片完整路径(生成的格式为：image/jpeg);
     * @throws Exception
     */
     public static void makeSmallImage(File srcImageFile,String dstImageFileName) throws Exception {
            FileOutputStream fileOutputStream = null;
            JPEGImageEncoder encoder = null;
            BufferedImage tagImage = null;
            Image srcImage = null;
            try{
                srcImage = ImageIO.read(srcImageFile);
                int srcWidth = srcImage.getWidth(null);//原图片宽度
                int srcHeight = srcImage.getHeight(null);//原图片高度
                int dstMaxSize = 120;//目标缩略图的最大宽度/高度，宽度与高度将按比例缩写
                int dstWidth = srcWidth;//缩略图宽度
                int dstHeight = srcHeight;//缩略图高度
                float scale = 0;
                //计算缩略图的宽和高
                if(srcWidth>dstMaxSize){
                    dstWidth = dstMaxSize;
                    scale = (float)srcWidth/(float)dstMaxSize;
                    dstHeight = Math.round((float)srcHeight/scale);
                }
                srcHeight = dstHeight;
                if(srcHeight>dstMaxSize){
                    dstHeight = dstMaxSize;
                    scale = (float)srcHeight/(float)dstMaxSize;
                    dstWidth = Math.round((float)dstWidth/scale);
                }
                //生成缩略图
                tagImage = new BufferedImage(dstWidth,dstHeight,BufferedImage.TYPE_INT_RGB);
                tagImage.getGraphics().drawImage(srcImage,0,0,dstWidth,dstHeight,null);
                fileOutputStream = new FileOutputStream(dstImageFileName);
                encoder = JPEGCodec.createJPEGEncoder(fileOutputStream);
                encoder.encode(tagImage);
                fileOutputStream.close();
                fileOutputStream = null;
            }finally{
                if(fileOutputStream!=null){
                    try{
                        fileOutputStream.close();
                    }catch(Exception e){
                    }
                    fileOutputStream = null;
                }
                encoder = null;
                tagImage = null;
                srcImage = null;
                System.gc();
            }
        }
}