简易验证码识别

try
{
string url = "http://tyt.gzsports.gov.cn/sport/image.jsp?key=0.9328223555348814";
WebRequest request = WebRequest.Create(url);
WebResponse response = request.GetResponse();
Stream st = response.GetResponseStream();

pic_CheckCode.Image = Image.FromStream(st);
Bitmap bitmap = new Bitmap(pic_CheckCode.Image);
UnCodebase ud = new UnCodebase(bitmap);
ud.GrayByPixels();
ud.ClearNoise(128, 2);

tessnet2.Tesseract ocr = new tessnet2.Tesseract();//声明一个OCR类
ocr.SetVariable("tessedit_char_whitelist", "0123456789abcdefghijklmnopqrstuvwxyzABCDEFGHIJKLMNOPQRSTUVWXYZ");
ocr.Init(@"E:\语言包路径", "eng", false);
List<tessnet2.Word> result = ocr.DoOCR(bitmap, Rectangle.Empty);//执行识别操作
string code = result[0].Text;
txt_Result.Text = code;
}
catch (Exception ex)
{
}