图片上传的工具类：生成缩略图，文件流转换。

可与struts2集成使用

import java.awt.Color;

import java.awt.Graphics2D;

import java.awt.Image;

import java.awt.image.BufferedImage;

import java.io.BufferedInputStream;

import java.io.BufferedOutputStream;

import java.io.ByteArrayOutputStream;

import java.io.File;

import java.io.FileInputStream;

import java.io.IOException;

import javax.imageio.ImageIO;

import org.apache.commons.logging.Log;

import org.apache.commons.logging.LogFactory;

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

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

public class FileUtil {

private static Log log = LogFactory.getLog(FileUtil.class);

public static byte[] toByteArray(File photo) throws IOException

{

FileInputStream fis = new FileInputStream(photo);

BufferedInputStream bis = new BufferedInputStream(fis);

ByteArrayOutputStream baos = new ByteArrayOutputStream();

int c = bis.read();

while (c != -1) {

baos.write(c);

c = bis.read();

}

bis.close();

byte[] rtn = baos.toByteArray();

baos.close();

return rtn;

}

public static byte[] buildThumbnail(File srcFile) {

byte[] rtn = null;

try {

Image src = ImageIO.read(srcFile); // 构造Image对象

int oldWidth = src.getWidth(null); // 得到源图宽

int oldHeight = src.getHeight(null);// 得到源图高

log.debug("old width is " + oldWidth);

log.debug("old height is " + oldHeight);

float divWidth = 200f; // 限制宽度为200

int newWidth = 200; // 缩略图宽,

int newHeight = 0; // 缩略图高

float tmp;

if (oldWidth > newWidth) {

tmp = oldWidth / divWidth;

newWidth = Math.round(oldWidth / tmp);// 计算缩略图高

newHeight = Math.round(oldHeight / tmp);// 计算缩略图高

log.debug("tmp scale is " + tmp);

} else {

newWidth = oldWidth;

newHeight = oldHeight;

}

int imageHeight = 100;

int imageWidth = 200;

log.debug("new width is " + newWidth);

log.debug("new height is " + newHeight);

BufferedImage bufferedImage = new BufferedImage(imageWidth,

imageHeight, BufferedImage.TYPE_INT_RGB);

Graphics2D graphics2D = (Graphics2D)

bufferedImage.createGraphics();

graphics2D.setBackground(Color.WHITE);

graphics2D.clearRect(0, 0, imageWidth, imageHeight);

bufferedImage.getGraphics().drawImage(src,

//(imageWidth - oldWidth) / 2, (imageHeight - newHeight) /

2,

0,0,

newWidth, newHeight, null); // 绘制缩小后的图

ByteArrayOutputStream baos = new ByteArrayOutputStream();

BufferedOutputStream bos = new BufferedOutputStream(baos);

JPEGImageEncoder encoder = JPEGCodec.createJPEGEncoder(bos);

encoder.encode(bufferedImage); // 近JPEG编码

rtn = baos.toByteArray();

bos.close();

baos.close();

} catch (Exception e) {

log.debug(e);

} finally {

}

return rtn;

}

}