如何用java压缩图片 生成缩略图

package com.util;

import java.awt.Image;
import java.awt.image.BufferedImage;
import java.io.File;
import java.io.FileNotFoundException;
import java.io.FileOutputStream;
import java.io.IOException;

import javax.imageio.ImageIO;

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

public class PicCompression {

public static String doCompress(String oldFile, int width, int height, float quality, String smallIcon, boolean percentage) {
if (oldFile != null && width > 0 && height > 0) {
String newImage = null;
try {
File file = new File(oldFile);
// 文件不存在
if (!file.exists()) {
return null;
}

Image srcFile = ImageIO.read(file);
int new_w = width;
int new_h = height;
if (percentage) {
// 为等比缩放计算输出的图片宽度及高度
double rate1 = ((double) srcFile.getWidth(null)) / (double) width + 0.1;
double rate2 = ((double) srcFile.getHeight(null)) / (double) height + 0.1;
double rate = rate1 > rate2 ? rate1 : rate2;
new_w = (int) (((double) srcFile.getWidth(null)) / rate);
new_h = (int) (((double) srcFile.getHeight(null)) / rate);
}

BufferedImage tag = new BufferedImage(new_w, new_h, BufferedImage.TYPE_INT_RGB);
tag.getGraphics().drawImage(srcFile, 0, 0, new_w, new_h, null);

String filePrex = oldFile.substring(0, oldFile.lastIndexOf(‘.’));
newImage = filePrex + smallIcon + oldFile.substring(filePrex.length());

FileOutputStream out = new FileOutputStream(newImage);

JPEGImageEncoder encoder = JPEGCodec.createJPEGEncoder(out);
JPEGEncodeParam jep = JPEGCodec.getDefaultJPEGEncodeParam(tag);

jep.setQuality(quality, true);
encoder.encode(tag, jep);

out.close();
srcFile.flush();

} catch (FileNotFoundException e) {
e.printStackTrace();
} catch (IOException e) {
e.printStackTrace();
}
return newImage;
} else {
return null;
}
}

//测试
public static void main(String str[]) {
System.out.println(PicCompression.doCompress(“F:/new.bmp”, 80, 50, 1, “_small”, false));
System.out.print(“ok…”);
}

}