import java.io.*;
import java.util.zip.GZIPInputStream;
import java.util.zip.GZIPOutputStream;

public class GzipUtils {
	
	public static byte[] gzip(byte[] data) throws Exception {
		ByteArrayOutputStream bos = new ByteArrayOutputStream();
		GZIPOutputStream gzip = new GZIPOutputStream(bos);
		gzip.write(data);
		gzip.finish();
		gzip.close();
		byte[] ret = bos.toByteArray();
		bos.close();
		return ret;
	}
	
	public static byte[] ungzip(byte[] data) throws Exception {
		ByteArrayInputStream bis = new ByteArrayInputStream(data);
		GZIPInputStream gzip = new GZIPInputStream(bis);
		byte[] buf = new byte[1024];
		int num = -1;
		ByteArrayOutputStream bos = new ByteArrayOutputStream();
		while((num = gzip.read(buf, 0, buf.length)) != -1){
			bos.write(buf,0,num);
		}
		gzip.close();
		bis.close();
		byte[] ret = bos.toByteArray();
		bos.flush();
		bos.close();
		return ret;
	}
	
    public static void main(String[] args) throws Exception {
        //讀取檔案
//        String readPath = System.getProperty("user.dir") + File.separatorChar + "sources" + File.separatorChar + "006.jpg";
        String readPath = "E:\\006.jpg";
        File file = new File(readPath);
		FileInputStream in = new FileInputStream(file);
		byte[] data = new byte[in.available()];
		in.read(data);
		in.close();
		System.out.println("檔案原始大小：" + data.length);
		
		//測試壓縮
		byte[] ret1 = GzipUtils.gzip(data);
		System.out.println("壓縮後大小" + ret1.length);
		
		byte[] ret2 = GzipUtils.ungzip(ret1);
		System.out.println("還原之後大小：" + ret2.length);
		
		//寫出檔案
		String writePath = "E:\\007.jpg";
		FileOutputStream fos = new FileOutputStream(writePath);
		fos.write(ret2);
		fos.close();
    }
}