Asp.net开发之webform图片水印和图片验证码的实现方法

<div>
<asp:fileupload id="fileupload1" runat="server" />
<asp:button id="button1" runat="server" text="上传" /><br />
<asp:image id="image1" runat="server" />
</div>

protected void page_load(object sender, eventargs e)
{
button1.click += button1_click;
}
void button1_click(object sender, eventargs e)
{
//1、制作画布
system.drawing.image img = system.drawing.image.fromstream(fileupload1.filecontent);
graphics g = graphics.fromimage(img);
//水印样式：画什么东西
string a = "http://www.itnba.com";
//字体、大小
font f = new font("黑体", 30);
//颜色
brush b = new solidbrush(color.red);
//0,0——开始画水印的位置
g.drawstring(a, f, b, 0, 0);
//保存路径
string path = "images/" + fileupload1.filename;
img.save(server.mappath(path));
//在image控件中展示
image1.imageurl = path;
}

<form id="form1" runat="server">
<div>
用户名：<asp:textbox id="textbox1" runat="server"></asp:textbox>
<br />
密码：<asp:textbox id="textbox2" runat="server"></asp:textbox>
<br />
验证码：<asp:textbox id="textbox3" runat="server"></asp:textbox>
<asp:image id="image1" runat="server" imageurl="yzm.aspx" />
<asp:label id="label1" runat="server" text="label"></asp:label>
<br />
<asp:button id="button1" runat="server" text="button" />
</div>
</form>
</body>
</html>
<script type="text/javascript">
var aaa = 1;
document.getelementbyid("image1").onclick = function () {
this.setattribute("src", "yzm.aspx?id=" + aaa);
aaa++;
};
</script>

protected void page_load(object sender, eventargs e)
{
random r = new random();
string aaa = "abcdefghijklmnopqrstuvwxyzabcdefghijklmnopqrstuvwxyz1234567890";
//生成画布
bitmap img = new bitmap(80, 30);
//画布背景色泛性组合
list<color> clist = new list<color>();
clist.add(color.yellow);
clist.add(color.green);
clist.add(color.blue);
clist.add(color.aqua);
clist.add(color.orange);
clist.add(color.pink);
graphics g = graphics.fromimage(img);
g.fillrectangle(new solidbrush(clist[r.next(0, clist.count)]), 0, 0, 80, 30);
//随机生成显示的验证码组合
string str = "";
for (int i = 0; i < 4; i++)
{
str += aaa.substring(r.next(0, aaa.length), 1);
}
session["yzm"] = str;
font f = new font("黑体", 20);
brush b = new solidbrush(color.red);
//生成
g.drawstring(str, f, b, 10, 0);
//添加干扰线
for (int i = 0; i < r.next(6, 20); i++)
{
brush bb = new solidbrush(clist[r.next(0, clist.count)]);
pen p = new pen(bb, 1);
g.drawline(p, r.next(0, 80), r.next(0, 30), r.next(0, 80), r.next(0, 30));
}
//保存完成
img.save(response.outputstream, system.drawing.imaging.imageformat.jpeg);
response.end();
}