Generating Captcha with image in C#
Below is the method used to make image and Store it in CaptchaImage folder.The image name will be saved in Table using store procedure SP_InserCaptcha
public dynamic GenrateCaptcha()
{
string otp = Numbergenerate();
string text = otp;
Bitmap bitmap = new Bitmap(1, 1);
Font font = new Font("Arial", 25, FontStyle.Regular, GraphicsUnit.Pixel);
Graphics graphics = Graphics.FromImage(bitmap);
int width = (int)graphics.MeasureString(text, font).Width;
int height = (int)graphics.MeasureString(text, font).Height;
bitmap = new Bitmap(bitmap, new Size(width, height));
graphics = Graphics.FromImage(bitmap);
graphics.Clear(Color.White);
graphics.SmoothingMode = SmoothingMode.AntiAlias;
graphics.TextRenderingHint = TextRenderingHint.AntiAlias;
graphics.DrawString(text, font, new SolidBrush(Color.FromArgb(255, 0, 0)), 0, 0);
graphics.Flush();
graphics.Dispose();
string fileName = Path.GetFileNameWithoutExtension(Path.GetRandomFileName()) + ".jpg";
bitmap.Save(HttpContext.Current.Server.MapPath("~/CaptchaImage/") + fileName, ImageFormat.Jpeg);
var data = db.SP_InserCaptcha(otp, fileName);
return otp;
}
Numbergenerate method generate random which will be used as captcha in image.It can be any digit.it will be great if we use alphanumeric captcha.
public string Numbergenerate()
{
string alphabets = "ABCDEFGHIJKLMNABCDEFGHIJKLMNPQRSTUVWXYZ";
string numbers = "123456789";
string characters = numbers;
characters += alphabets + numbers;
int length = 6;
string otp = string.Empty;
for (int i = 0; i < length; i++)
{
string character = string.Empty;
do
{
int index = new Random().Next(0, characters.Length);
character = characters.ToCharArray()[index].ToString();
}
while (otp.IndexOf(character) != -1);
otp += character;
}
return otp;
}
Below is the store procedure used in SQL to save captcha image and captcha with uniqe captcha id which will be used later to validate captcha
Create Proc SP_InserCaptcha
(@Otp nvarchar(8),@CaptchaImg nvarchar(max))
as
begin
if((select count(Captcha) from TblCaptcha) =1000)
Truncate table TblCaptcha
Insert Into TblCaptcha (Captcha,CatchaImage) values(@Otp,@CaptchaImg)
select top(1)CaptchaID,CatchaImage from TblCaptcha
order by CaptchaID desc
end
Here is the table that is used to store captcha with captcha id.
CREATE TABLE [dbo].[TblCaptcha](
[CaptchaID] [int] IDENTITY(1,1) NOT NULL,
[CatchaImage] [nvarchar](64) NULL,
[Captcha] [nvarchar](64) NULL)
