java验证码Captcha

import java.awt.Color;
import java.io.IOException;
import java.util.Random;

import javax.servlet.http.HttpServletResponse;

import org.patchca.color.ColorFactory;
import org.patchca.filter.predefined.CurvesRippleFilterFactory;
import org.patchca.filter.predefined.DiffuseRippleFilterFactory;
import org.patchca.filter.predefined.DoubleRippleFilterFactory;
import org.patchca.filter.predefined.MarbleRippleFilterFactory;
import org.patchca.filter.predefined.WobbleRippleFilterFactory;
import org.patchca.service.ConfigurableCaptchaService;
import org.patchca.utils.encoder.EncoderHelper;
import org.patchca.word.RandomWordFactory;

public class CaptchaUtil {

private static ConfigurableCaptchaService cs = new ConfigurableCaptchaService();
private static Random random = new Random();

static {
cs.setColorFactory(new ColorFactory() {
@Override
public Color getColor(int x) {
int[] c = new int[3];
int i = random.nextInt(c.length);
for (int fi = 0; fi < c.length; fi++) {
if (fi == i) {
c[fi] = random.nextInt(71);
} else {
c[fi] = random.nextInt(256);
}
}
return new Color(c[0], c[1], c[2]);
}
});
RandomWordFactory wf = new RandomWordFactory();
wf.setCharacters("23456789abcdefghigkmnpqrstuvwxyzABCDEFGHIGKLMNPQRSTUVWXYZ");
wf.setMaxLength(4);
wf.setMinLength(4);
cs.setWordFactory(wf);
}

public static String generate(HttpServletResponse response) throws IOException{
switch (random.nextInt(5)) {
case 0:
cs.setFilterFactory(new CurvesRippleFilterFactory(cs.getColorFactory()));
break;
case 1:
cs.setFilterFactory(new MarbleRippleFilterFactory());
break;
case 2:
cs.setFilterFactory(new DoubleRippleFilterFactory());
break;
case 3:
cs.setFilterFactory(new WobbleRippleFilterFactory());
break;
case 4:
cs.setFilterFactory(new DiffuseRippleFilterFactory());
break;
}
setResponseHeaders(response);
return EncoderHelper.getChallangeAndWriteImage(cs, "png", response.getOutputStream());
}

private static void setResponseHeaders(HttpServletResponse response) {
response.setContentType("image/png");
response.setHeader("Cache-Control", "no-cache, no-store");
response.setHeader("Pragma", "no-cache");
long time = System.currentTimeMillis();
response.setDateHeader("Last-Modified", time);
response.setDateHeader("Date", time);
response.setDateHeader("Expires", time);
}
}