一、水印

1.畫布

System.Drawing.Image img = System.Drawing.Image.FromStream(FileUpload1.FileContent);

2.創(chuàng)建繪制對象，告訴它往哪張圖片上繪制

Graphics g = Graphics.FromImage(img);

3.繪制的內(nèi)容

string s = <a href="http://m.miracleart.cn">m.miracleart.cn</a>;

4.繪制的字體

Font f = new Font("黑體",130);

5.繪制的畫刷

Brush b = new SolidBrush(Color.Red);

6.開始繪制

g.DrawString(s, f, b, 5, 5);

二、圖片驗證碼

Bitmap bit = new Bitmap(90, 40);//畫布大小
    Graphics g = Graphics.FromImage(bit);//創(chuàng)建繪制對象，告訴它往哪張圖片上繪制
    Random r = new Random();
    string s = "";
    Color color1 = Color.FromArgb(r.Next(155, 255), r.Next(155, 255), r.Next(155, 255));
    g.FillRectangle(new SolidBrush(color1), 0, 0, 90, 40);//畫布顏色隨機
    for (int i = 0; i < 10; i++)//隨機畫干擾線
    {
      Color color3 = Color.FromArgb(r.Next(170, 255), r.Next(190, 255), r.Next(170, 255));
      Pen pp = new Pen(new SolidBrush(color3), r.Next(0, 5));
      g.DrawLine(pp, r.Next(0, 90), r.Next(0, 40), r.Next(0, 90), r.Next(0, 40));
    }
    string yan = "abcdefghijklmnopqrstuvwxyzABCDEFGHIJKLMNOPQRSTUVWXYZ1234567890";//設(shè)置隨機的驗證碼，從里面抽取
    int wei = 0;
    for (int i = 0; i < 4; i++)//取四位驗證碼，顏色隨機
    {
      string m = yan.Substring(r.Next(0, yan.Length), 1);
      s += m;
      Color color2 = Color.FromArgb(r.Next(0, 155), r.Next(0, 155), r.Next(0, 155));
      int w = r.Next(20, 25);
      Font f = new Font("黑體", w);
      SolidBrush b = new SolidBrush(color2);
      g.DrawString(m, f, b, wei, r.Next(0, 10));
      wei += w;
    }
    Session["YZM"] = s;//把驗證碼保存到session中
    for (int i = 0; i < 251; i++)
    {
      Color color3 = Color.FromArgb(r.Next(0, 255), r.Next(0, 255), r.Next(0, 255));
      Pen pp = new Pen(new SolidBrush(color3), r.Next(0, 5));
      int a = r.Next(0, 90);
      int b = r.Next(0, 40);
      g.DrawLine(pp, a, b, (a + 1), (b + 1));
    }
    bit.Save(Response.OutputStream, System.Drawing.Imaging.ImageFormat.Jpeg);
    Response.End();

驗證碼：

<asp:TextBox ID="TextBox3" runat="server"></asp:TextBox>
    <asp:Image ID="Image1" runat="server" ImageUrl="Default2.aspx" />//這里圖片路徑不是一張圖片的話會默認打開

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以上所述是小編給大家分享的Web前端開發(fā)之水印、圖片驗證碼，希望對大家有所幫助