import java.awt.Image;
import java.awt.image.BufferedImage;
import java.io.File;
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.JPEGImageEncoder;
public class JpgChange {
    // path 路徑 ,舊文件名稱 ,新文件名稱,n 改變倍數
    public void changeImage(String path, String oldimg, String newimg, int n) {
       try {
           File file = new File(path + oldimg);
           Image img = ImageIO.read(file);
           // 構造Image對象
           int wideth = img.getWidth(null); // 得到源圖寬
           int height = img.getHeight(null); // 得到源圖長
           BufferedImage tag = new BufferedImage(n * wideth, n * height,
                  BufferedImage.TYPE_INT_RGB);
           tag.getGraphics().drawImage(img, 0, 0, n * wideth, n * height, null);
           FileOutputStream out = new FileOutputStream(path + newimg);
           JPEGImageEncoder encoder = JPEGCodec.createJPEGEncoder(out);
           encoder.encode(tag); // 近JPEG編碼
           out.close();
       } catch (IOException e) {
           System.out.println("處理文件出現異常");
           e.printStackTrace();
       }
    }
    public static void main(String[] args) {
       JpgChange jc = new JpgChange();
       jc.changeImage("E://", "1.bmp", "2.bmp", 3);
    }
}