java程序：为图片文件生成缩略图

package ImageTest; 
import java.awt.Graphics2D; 
import java.awt.RenderingHints; 
import java.awt.geom.AffineTransform; 
import java.awt.image.BufferedImage; 
import java.awt.image.ColorModel; 
import java.awt.image.WritableRaster; 
import java.io.File; 
import java.io.IOException; 
import javax.imageio.ImageIO; 
public class Test { 
    /** 
     * 为图片文件生成缩略图 
     * @param args 
     */
    public static void main(String\[\] args) { 
        try { 
            //参数1（源图片路径），参数2 （缩略图路径），参数3（缩略图宽）参数4（缩略图高） 
            Test.saveImageAsJpg("E:\\\\QQ20120612154244.gif", "E:\\\\test.jpg", 400, 400); 
        } catch (IOException e) { 
            e.printStackTrace(); 
        } 
    } 
    /** 
     * 生成缩略图 
     * @param fromFileStr 源图片路径 
     * @param saveToFileStr 缩略图路径 
     * @param width 缩略图的宽 
     * @param hight 缩略图的高 
     * @throws IOException 
     */
    public static void saveImageAsJpg(String fromFileStr,String saveToFileStr,int width,int hight) throws IOException 
    { 
        BufferedImage srcImage; 
        String imgType="JPEG"; 
        if(fromFileStr.toLowerCase().endsWith(".png")){ 
            imgType="PNG"; 
        } 
        File saveFile=new File(saveToFileStr); 
        File fromFile=new File(fromFileStr); 
        srcImage=ImageIO.read(fromFile); 
        if(width>0||hight>0){ 
            srcImage=resize(srcImage,width,hight); 
        } 
        ImageIO.write(srcImage, imgType, saveFile); 
    } 
    /** 
     * 将源图片的BufferedImage对象生成缩略图 
     * @param source 源图片的BufferedImage对象 
     * @param targetW 缩略图的宽 
     * @param targetH 缩略图的高 
     * @return 
     */
    private static BufferedImage resize(BufferedImage source, int targetW, 
            int targetH) { 
        int type=source.getType(); 
        BufferedImage target=null; 
        double sx=(double)targetW/source.getWidth(); 
        double sy=(double)targetH/source.getHeight(); 
        if(sx>sy) 
        { 
            sx=sy; 
            targetW=(int)(sx*source.getWidth()); 
        }else{ 
            sy=sx; 
            targetH=(int)(sy*source.getHeight()); 
        } 
        if(type==BufferedImage.TYPE_CUSTOM){ 
            ColorModel cm=source.getColorModel(); 
                WritableRaster raster=cm.createCompatibleWritableRaster(targetW, targetH); 
                boolean alphaPremultiplied=cm.isAlphaPremultiplied(); 
                target=new BufferedImage(cm,raster,alphaPremultiplied,null); 
        }else{ 
            target=new BufferedImage(targetW, targetH,type); 
        } 
        Graphics2D g=target.createGraphics(); 
        g.setRenderingHint(RenderingHints.KEY_RENDERING, RenderingHints.VALUE_RENDER_QUALITY); 
        g.drawRenderedImage(source, AffineTransform.getScaleInstance(sx, sy)); 
        g.dispose(); 
        return target; 
    } 
}