它能处理网页上大多数图片,bmp除外,本着共享的原则,大家如果觉得有用就拿去吧.
package utils;
import java.awt.Graphics;
import java.awt.GraphicsConfiguration;
import java.awt.GraphicsDevice;
import java.awt.GraphicsEnvironment;
import java.awt.HeadlessException;
import java.awt.Image;
import java.awt.Transparency;
import java.awt.image.BufferedImage;
import java.awt.image.ColorModel;
import java.awt.image.PixelGrabber;
import java.io.File;
import java.text.SimpleDateFormat;
import java.util.Calendar;
import java.util.GregorianCalendar;
import javax.imageio.ImageIO;
import javax.swing.ImageIcon;
import utils.bean.Size;
public class PictureUtil {
 // This method returns a buffered image with the contents of an image
 public static BufferedImage toBufferedImage(Image image) {
   if (image instanceof BufferedImage) {
     return (BufferedImage) image;
   }
   // This code ensures that all the pixels in the image are loaded
   image = new ImageIcon(image).getImage();
   // Determine if the image has transparent pixels; for this method's
   // implementation, see e661 Determining If an Image Has Transparent
   // Pixels
   boolean hasAlpha = hasAlpha(image);
   // Create a buffered image with a format that's compatible with the
   // screen
   BufferedImage bimage = null;
   GraphicsEnvironment ge = GraphicsEnvironment
       .getLocalGraphicsEnvironment();
   try {
     // Determine the type of transparency of the new buffered image
     int transparency = Transparency.OPAQUE;
     if (hasAlpha) {
       transparency = Transparency.BITMASK;
     }
     // Create the buffered image
     GraphicsDevice gs = ge.getDefaultScreenDevice();
     GraphicsConfiguration gc = gs.getDefaultConfiguration();
     bimage = gc.createCompatibleImage(image.getWidth(null), image
         .getHeight(null), transparency);
   } catch (HeadlessException e) {
     // The system does not have a screen
   }
   if (bimage == null) {
     // Create a buffered image using the default color model
     int type = BufferedImage.TYPE_INT_RGB;
     if (hasAlpha) {
       type = BufferedImage.TYPE_INT_ARGB;
     }
     bimage = new BufferedImage(image.getWidth(null), image
         .getHeight(null), type);
   }
   // Copy image to buffered image
   Graphics g = bimage.createGraphics();
   // Paint the image onto the buffered image
   g.drawImage(image, 0, 0, null);
   g.dispose();
   return bimage;
 }
 public static boolean hasAlpha(Image image) {
   // If buffered image, the color model is readily available
   if (image instanceof BufferedImage) {
     BufferedImage bimage = (BufferedImage) image;
     return bimage.getColorModel().hasAlpha();
   }
   // Use a pixel grabber to retrieve the image's color model;
   // grabbing a single pixel is usually sufficient
   PixelGrabber pg = new PixelGrabber(image, 0, 0, 1, 1, false);
   try {
     pg.grabPixels();
   } catch (InterruptedException e) {
   }
   // Get the image's color model
   ColorModel cm = pg.getColorModel();
   return cm.hasAlpha();
 }
// 取得文件更新时间
 public static String getLastModifyTime(long modifiedTime) {
   Calendar cal = new GregorianCalendar();
   cal.setTimeInMillis(modifiedTime);
   SimpleDateFormat fromatter = new SimpleDateFormat("yyyy-MM-dd HH:mm:ss");
   String lastModifyTime = fromatter.format(cal.getTime());
   return lastModifyTime;
 }
// 取得文件扩展名
 public static String getFileExtension(String fileName) {
   return fileName.substring(fileName.lastIndexOf(".") + 1, fileName
       .length());
 }
// 取得图片大小,Size类很简单,自己写吧.
 public static Size getPictureSize(String fileName) throws Exception{
   File file=new File(fileName);
   BufferedImage bufferIamge=PictureUtil.toBufferedImage(ImageIO.read(file));
   return new Size(bufferIamge.getWidth(),bufferIamge.getHeight());
 }
}