按实际上传时的文件名称保存（不在是test.jpg了）图片可以改大小，图上写字（可选字体，我设的全是中文，^_^。大小），没有解决字体颜色问题。
<%@ Page Language="c#" Debug="true" Trace="true"%>
<%@ Import Namespace="System.IO" %>
<%@ Import Namespace="System.Drawing" %>
<%@ Import Namespace="System.Drawing.Imaging" %>
<html>
<script runat =server>
void UploadBtn_Click(Object sender, EventArgs e) {
String filename;
String filename1;
String[] filename2;
int q;
filename=UploadFile.PostedFile.FileName ;
filename2=filename.Split(new Char[] {'\\'});
q=filename2.GetUpperBound(0);
filename1=filename2[q];
dis.Text="上传文件名："+filename1+"<br>";
UploadFile.PostedFile.SaveAs(Server.MapPath(filename1));
ImageEditor.Visible = true;
dis.Text+="文件大小："+UploadFile.PostedFile.ContentLength+"字节数";
Image1.Src=filename1;
}
void UpdateBtn_Click(Object sender, EventArgs e) {
String filename1;
filename1=Image1.Src;
System.Drawing.Image image = System.Drawing.Image.FromFile(Server.MapPath(filename1));
System.Drawing.Image newimage = new Bitmap(image.Width, image.Height, PixelFormat.Format32bppRGB);
Graphics g = Graphics.FromImage(newimage);
g.DrawImage(image,0,0,image.Width,image.Height);
Font f = new Font(FontType.SelectedItem.Text, Int32.Parse(FontSize.SelectedItem.Text));
Brush b = new SolidBrush(Color.Red);
g.DrawString(Caption.Text, f, b, 10, 140);
g.Dispose();
System.Drawing.Image thumbImage = newimage.GetThumbnailImage(Int32.Parse(Width.Text),Int32.Parse(Height.Text),null,0);
image.Dispose();
thumbImage.Save(Server.MapPath(filename1), ImageFormat.JPEG);
Image1.Src=filename1;
Caption.Text="";
}
</script>
<body>
<asp:label id="dis" runat=server/>
<form enctype="multipart/form-data" runat=server>
<h3>
Select File To Upload: <input id="UploadFile" type=file runat=server>
<asp:button Text="Upload Me!" runat=server/>
<hr>
<asp:panel id="ImageEditor" Visible=false runat=server>
<img ID="Image1" src="" runat="server"/>
<h3>
Image Width: <asp:textbox id="Width" runat=server/>
Image Height: <asp:textbox id="Height" runat=server/> <br>
Text Caption: <asp:textbox id="Caption" runat=server/>
Caption Size: <asp:dropdownlist id="FontSize" runat=server>
<asp:listitem>14</asp:listitem>
<asp:listitem>18</asp:listitem>
<asp:listitem>26</asp:listitem>
<asp:listitem>36</asp:listitem>
<asp:listitem>48</asp:listitem>
<asp:listitem>62</asp:listitem>
</asp:dropdownlist>
Caption Font: <asp:dropdownlist id="FontType" runat=server>
<asp:listitem>黑体</asp:listitem>
<asp:listitem>仿宋</asp:listitem>
<asp:listitem>隶书</asp:listitem>
<asp:listitem>楷书</asp:listitem>
<asp:listitem>方正姚体</asp:listitem>
<asp:listitem>华文彩云</asp:listitem>
</asp:dropdownlist>
<asp:button Text="Update Image" runat=server/>
</h3>
</asp:panel>
</form>
</body>
</html>