Simple yet powerful verification code library written in Java with zero dependency.
You can generate verification code picture like this:
ConfigurableCaptchaService cs = new ConfigurableCaptchaService();
cs.setColorFactory(new SingleColorFactory(new Color(25, 60, 170)));
cs.setFilterFactory(new CurvesRippleFilterFactory(cs.getColorFactory()));
FileOutputStream fos = new FileOutputStream("patcha_demo.png");
EncoderHelper.getChallangeAndWriteImage(cs, "png", fos);
fos.close();it generate picture like this: