文件名称：ASP.net中的验证码技术
文件大小：3KB
文件格式：TXT
更新时间：2014-07-24 08:59:03
验证码技术
System.Random rand = new Random();
int len = rand.Next(4 , 6 );
char[] chars = "0123456789ABCDEFGHIJKLMNOPQRSTUVWXYZ".ToCharArray();
System.Text.StringBuilder myStr = new System.Text.StringBuilder();
for( int iCount = 0 ; iCount < len ; iCount ++ )
{
myStr.Append( chars[ rand.Next( chars.Length )]);
}
string text = myStr.ToString();
// 保存验证码到 session 中以便其他模块使用
this.Session["checkcode"] = text ;
Size ImageSize = Size.Empty ;
Font myFont = new Font("MS Sans Serif" , 20 );
// 计算验证码图片大小
using( Bitmap bmp = new Bitmap( 10 , 10 ))
{
using( Graphics g = Graphics.FromImage( bmp ))
{
SizeF size = g.MeasureString( text , myFont , 10000 );
ImageSize.Width = ( int ) size.Width + 8 ;
ImageSize.Height = ( int ) size.Height + 8 ;
}
}
// 创建验证码图片
using( Bitmap bmp = new Bitmap( ImageSize.Width , ImageSize.Height ))
{
// 绘制验证码文本
using( Graphics g = Graphics.FromImage( bmp ))
{
g.Clear( Color.White );
using( StringFormat f = new StringFormat())
{
f.Alignment = StringAlignment.Near ;
f.LineAlignment = StringAlignment.Center ;
f.FormatFlags = StringFormatFlags.NoWrap ;
g.DrawString(
text ,
myFont ,
Brushes.Black ,
new RectangleF(
0 ,
0 ,
ImageSize.Width ,
ImageSize.Height ),
f );
}//using
}//using
// 制造噪声 杂点面积占图片面积的 30%
int num = ImageSize.Width * ImageSize.Height * 30 / 100 ;
for( int iCount = 0 ; iCount < num ; iCount ++ )
{
// 在随机的位置使用随机的颜色设置图片的像素
int x = rand.Next( ImageSize.Width );
int y = rand.Next( ImageSize.Height );
int r = rand.Next( 255 );
int g = rand.Next( 255 );
int b = rand.Next( 255 );
Color c = Color.FromArgb( r , g , b );
bmp.SetPixel( x , y , c );
}//for
// 输出图片
System.IO.MemoryStream ms = new System.IO.MemoryStream();
bmp.Save( ms , System.Drawing.Imaging.ImageFormat.Png );
this.Response.ContentType = "image/png";
ms.WriteTo( this.Response.OutputStream );
ms.Close();
}//using
myFont.Dispose();