/// summary>
/// 生成验证码图片，保存session名称VerificationCode
/// /summary>
public static void CreateVerificationCode()
{
int number;
string checkCode = string.Empty;
//随机数种子
Random randoms = new Random();
for (int i = 0; i 4; i++) //校验码长度为4
{
//随机的整数
number = randoms.Next();
//字符从0-9,A-Z中随机产生,对应的ASCII码分别为
//48-57,65-90
number = number % 36;
if (number 10)
{
number += 48;
}
else
{
number += 55;
}
checkCode += ((char)number).ToString();
}
//在session中保存校验码
System.Web.HttpContext.Current.Session["VerificationCode"] = checkCode;
//若校验码为空，则直接返回
if (checkCode == null || checkCode.Trim() == String.Empty)
{
return;
}
//根据校验码的长度确定输出图片的长度
System.Drawing.Bitmap image = new System.Drawing.Bitmap(55, 20);//(int)Math.Ceiling(Convert.ToDouble(checkCode.Length * 15))
//创建Graphics对象
Graphics g = Graphics.FromImage(image);
try
{
//生成随机数种子
Random random = new Random();
//清空图片背景色
g.Clear(Color.White);
//画图片的背景噪音线 10条
//---------------------------------------------------
for (int i = 0; i 10; i++)
{
//噪音线起点坐标(x1,y1),终点坐标(x2,y2)
int x1 = random.Next(image.Width);
int x2 = random.Next(image.Width);
int y1 = random.Next(image.Height);
int y2 = random.Next(image.Height);
//用银色画出噪音线
g.DrawLine(new Pen(Color.Silver), x1, y1, x2, y2);
}
//---------------------------------------------------
//Brush b = Brushes.Silver;
//g.FillRectangle(b, 0, 0, image.Width, image.Height);
//---------------------以上两种任选其一------------------------------
//输出图片中校验码的字体: 12号Arial,粗斜体
Font font = new Font("Arial", 12, (FontStyle.Bold | FontStyle.Italic));
//线性渐变画刷
LinearGradientBrush brush = new LinearGradientBrush(new Rectangle(0, 0, image.Width, image.Height), Color.Blue, Color.Purple, 1.2f, true);
g.DrawString(checkCode, font, brush, 2, 2);
//画图片的前景噪音点 50个
for (int i = 0; i 50; i++)
{
int x = random.Next(image.Width);
int y = random.Next(image.Height);
image.SetPixel(x, y, Color.FromArgb(random.Next()));
}
//画图片的边框线
g.DrawRectangle(new Pen(Color.Peru), 0, 0, image.Width - 1, image.Height - 1);
//创建内存流用于输出图片
using (MemoryStream ms = new MemoryStream())
{
//图片格式指定为png
image.Save(ms, ImageFormat.Jpeg);
//清除缓冲区流中的所有输出
System.Web.HttpContext.Current.Response.ClearContent();
//输出流的HTTP MIME类型设置为"image/Png"
System.Web.HttpContext.Current.Response.ContentType = "image/Jpeg";
//输出图片的二进制流
System.Web.HttpContext.Current.Response.BinaryWrite(ms.ToArray());
}
}
finally
{
//释放Bitmap对象和Graphics对象
g.Dispose();
image.Dispose();
}
}
