JAVA技术：上传图片的缩放处理

import java.io.File;

import java.awt.image.BufferedImage;

import java.awt.Image;

import java.awt.image.AffineTransformOp;

import javax.imageio.ImageIO;

import java.awt.geom.AffineTransform;
public class UploadImg{
/**

* @param fromdir 图片的原始目录

* @param todir 处理后的图片存放目录

* @param imgfile 原始图片

* @param sysimgfile 处理后的图片文件名前缀

*

*/ 

............................ 

public boolean CreateThumbnail() throws Exception

{

//ext是图片的格式 gif JPG 或png

String ext="";

double Ratio=0.0;

File F = new File(fromdir,imgfile);

if (!F.isFile())

throw new Exception(F+" is not image file error in CreateThumbnail!");
//首先判断上传的图片是gif还是JPG ImageIO只能将gif转换为png

if (isJpg(imgfile)){

ext="jpg";

}else{

ext="png"; 

}

File ThF = new File(todir,sysimgfile+"."+ext); 
BufferedImage Bi = ImageIO.read(F);

//假设图片宽 高 最大为120 120

Image Itemp = Bi.getScaledInstance (120,120,Bi.SCALE_SMOOTH);
if ((Bi.getHeight()>120) || (Bi.getWidth()>120)){

if (Bi.getHeight()>Bi.getWidth())

Ratio = 120.0/Bi.getHeight();

else

Ratio = 120.0/Bi.getWidth();

}
AffineTransformOp op = new AffineTransformOp(AffineTransform.getScaleInstance
(Ratio, Ratio), null);

Itemp = op.filter(Bi, null);
try {

ImageIO.write((BufferedImage)Itemp, ext, ThF);

}catch (Exception ex) {

throw new Exception(" ImageIo.write error in CreatThum.: "+ex.getMessage()); 

}

return (true);

}

}