图片加水印
1 获取这张图片
System.Drawing.Image img = System.Drawing.Image.FromStream(FileUpload1.FileContent);
2 给图片加水印
Graphics g = Graphics.FromImage(img);
string s = "WWW.ITNBA.COM"; s 给图片加的水印文字
Font f = new Font("微软雅黑", 30);
Brush b = new SolidBrush(Color.Red);
PointF pf = new PointF(50, 50);
g.DrawString(s, f, b, pf);
3 保存这张图
string path = "Uploads/" + DateTime.Now.ToString("yyyyMMddhhmmssms") + FileUpload1.FileName;
img.Save(Server.MapPath(path));
Image1.ImageUrl = path;
网页保存这张图回事aspx格式 将后缀改成png格式即可查看图片
小知识 ： 图片转换成txt格式 会出现乱码 在乱码下方添加 文字 再转换成jpg个是不会影响图片
图片格式的验证码
List<Color> clist = new List<Color>(); clist.Add(Color.Red); clist.Add(Color.Firebrick); clist.Add(Color.LawnGreen); clist.Add(Color.Goldenrod); clist.Add(Color.Cyan); clist.Add(Color.DarkSlateBlue); clist.Add(Color.Indigo); Random r = new Random(); string s = ""; string all = "ABCDEFGHIJKLMNOPQRSTUVWXYZabcdefghijklmeopqrstuvwxyz0123456789"; for (int i = 0; i < 4; i++) { s += all.Substring(r.Next(0, all.Length), 1); } Session["YZM"] = s; Bitmap img = new Bitmap(120, 60); Graphics g2 = Graphics.FromImage(img); Brush b2 = new SolidBrush(clist[r.Next(0, clist.Count)]); g2.FillRectangle(b2, 0, 0, 120, 60); Graphics g = Graphics.FromImage(img); Font f = new Font("微软雅黑", 30); Brush b = new SolidBrush(Color.Red); g.DrawString(s, f, b, new PointF(0, 0)); for (int i = 0; i < 8; i++) { Graphics g3 = Graphics.FromImage(img); Pen p3 = new Pen(new SolidBrush(clist[r.Next(0, clist.Count)]), r.Next(2, 5)); g3.DrawLine(p3, new Point(r.Next(0, 120), r.Next(0, 60)), new Point(r.Next(0, 120), r.Next(0, 60))); } img.Save(Response.OutputStream, System.Drawing.Imaging.ImageFormat.Png);
前台验验证 验证码
var a = 0;
document.getElementById("yzm1").onclick = function () {
this.src = "yzm.aspx?a=" + a;
a++;
}
点击图片 切换验证码 方正验证码 图片重复 打开的验证码图片 传个值 这个值用不到
就可以实现 图片 无限刷新
toUpperCase 实现验证码大小写转换
原文：http://www.cnblogs.com/v587yy/p/6971356.html
