// 生成jpg的缩略图-----------------------------------------------------
// 新的缩略图保存地址 

String miniFileName = request.getRealPath("/") + "upload/"+subdir
+ datedir + filename + "_min" + "." + ext;// 新的缩略图保存地址

uploadMiniURL = "http://www.itale.cn/upload/"+ datedir + filename + "_min" + "." + ext;
miniFileName = request.getRealPath("/") + "upload/" + datedir + filename + "_min" + "." + ext; 
java.io.File file = new java.io.File(uploadFileName);// 读入刚才上传的文件
Image src = javax.imageio.ImageIO.read(file);// 构造Image对象
float tagsize = 200;
int old_w = src.getWidth(null);// 得到源图宽
int old_h = src.getHeight(null);
int new_h = 0;// 得到源图长
int new_w = 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);
// 输出到文件流
FileOutputStream newimage = new FileOutputStream(miniFileName);
JPEGImageEncoder encoder = JPEGCodec.createJPEGEncoder(newimage);
encoder.encode(tag);// 近JPEG编码
newimage.close();