获得CSDN的验证码

import java.awt.Image;
import java.awt.image.BufferedImage;
import java.io.BufferedInputStream;
import java.io.FileOutputStream;
import java.io.InputStreamReader;
import java.io.Reader;
import java.net.URL;
import java.net.URLConnection;

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

public class TestUrl {
public static void main(String[] args) throws Exception {
// String s = "http://passport.csdn.net/UserLogin.aspx";
// URL url = new URL(s);
// URLConnection uc = url.openConnection();
// // 打开的连接读取的输入流。
// Reader reader = new InputStreamReader(new
// BufferedInputStream(url.openStream()));
// int c;
// while ((c = reader.read()) != -1) {
// System.out.print((char) c);
// }
// reader.close();
String url = "http://passport.csdn.net/ShowExPwd.aspx"; // CSDN验证码地址
getImg(url);
}

public static void getImg(String url) throws Exception {
URL u = new URL(url);
for (int j = 0; j < 10; j++) { //得到10张。如果想做研究，可以循环1W次试试看。。。
JpgTset(u, j);
}

}

public static void JpgTset(URL url, int i) throws Exception {
Image src = javax.imageio.ImageIO.read(url); // 构造Image对象
int wideth = src.getWidth(null); // 得到源图宽
int height = src.getHeight(null); // 得到源图长
BufferedImage tag = new BufferedImage(wideth / 2, height / 2,
BufferedImage.TYPE_INT_RGB);
tag.getGraphics().drawImage(src, 0, 0, wideth / 2, height / 2, null); // 绘制缩小后的图
FileOutputStream out = new FileOutputStream("c:/image/" + i + ".jpg"); // 输出到文件流
JPEGImageEncoder encoder = JPEGCodec.createJPEGEncoder(out);
encoder.encode(tag); // 近JPEG编码
// System.out.print(width+"*"+height);
out.close();
}
}