ASP.NET 实现验证码以及刷新验证码的小例子(2)

//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();
        }
    }