实现过程：选择图片上传成功后，取得已经存在服务器的文件生成缩略图，并且判断是否是图片类型的文件，这个的判断可以在程序中修改，本程序只是判断了“image/bmp”、“image/gif”、“image/pjpeg”三种类型。
代码如下：
upfile.aspx文件
<%@ Page Language="C#" AutoEventWireup="true" CodeFile="upfile.aspx.cs" Inherits="upfile_upfile" %>
<!DOCTYPE html PUBLIC "-//W3C//DTD XHTML 1.0 Transitional//EN" "http://www.w3.org/TR/xhtml1/DTD/xhtml1-transitional.dtd">
<html xmlns="http://www.w3.org/1999/xhtml" >
<head runat="server">
<title>无标题页</title>
</head>
<body>
<form runat="server">
<div>
<asp:FileUpload runat="server" />
<asp:Button runat="server" Text="上传" /><br />
<asp:Label runat="server"></asp:Label></div>
</form>
</body>
</html>
upfile.aspx.cs文件
using System;
using System.Data;
using System.Configuration;
using System.Collections;
using System.Web;
using System.Web.Security;
using System.Web.UI;
using System.Web.UI.WebControls;
using System.Web.UI.WebControls.WebParts;
using System.Web.UI.HtmlControls;
using System.IO;
public partial class upfile_upfile : System.Web.UI.Page
{
protected void Page_Load(object sender, EventArgs e)
{ }
protected void Button1_Click(object sender, EventArgs e)
{
if (FileUpload1.HasFile)
{
string fileContentType = FileUpload1.PostedFile.ContentType;
if (fileContentType == "image/bmp" || fileContentType == "image/gif" || fileContentType == "image/pjpeg")
{
string name = FileUpload1.PostedFile.FileName; // 客户端文件路径
FileInfo file = new FileInfo(name);
string fileName = file.Name; // 文件名称
string fileName_s = "s_" + file.Name; // 缩略图文件名称
string fileName_sy = "sy_" + file.Name; // 水印图文件名称（文字）
string fileName_syp = "syp_" + file.Name; // 水印图文件名称（图片）
string webFilePath = Server.MapPath("file/" + fileName); // 服务器端文件路径
string webFilePath_s = Server.MapPath("file/" + fileName_s); // 服务器端缩略图路径
string webFilePath_sy = Server.MapPath("file/" + fileName_sy); // 服务器端带水印图路径(文字)
string webFilePath_syp = Server.MapPath("file/" + fileName_syp); // 服务器端带水印图路径(图片)
string webFilePath_sypf = Server.MapPath("file/shuiyin.jpg"); // 服务器端水印图路径(图片)
if (!File.Exists(webFilePath))
{
try
{
FileUpload1.SaveAs(webFilePath);
AddShuiYinWord(webFilePath, webFilePath_sy);
AddShuiYinPic(webFilePath, webFilePath_syp, webFilePath_sypf);
MakeThumbnail(webFilePath, webFilePath_s, 130, 130, "Cut"); // 生成缩略图方法
Label1.Text = "提示：文件“" + fileName + "”成功上传，并生成“" + fileName_s + "”缩略图，文件类型为：" + FileUpload1.PostedFile.ContentType + "，文件大小为：" + FileUpload1.PostedFile.ContentLength + "B";
}
catch (Exception ex)
{
Label1.Text = "提示：文件上传失败，失败原因：" + ex.Message;
}
}
else
{
Label1.Text = "提示：文件已经存在，请重命名后上传";
}
}
else
{
Label1.Text = "提示：文件类型不符";
}
}
}
/**//// <summary>
/// 生成缩略图
/// </summary>
/// <param>源图路径（物理路径）</param>
/// <param>缩略图路径（物理路径）</param>
/// <param>缩略图宽度</param>
/// <param>缩略图高度</param>
/// <param>生成缩略图的方式</param>
public static void MakeThumbnail(string originalImagePath, string thumbnailPath, int width, int height, string mode)
{
System.Drawing.Image originalImage = System.Drawing.Image.FromFile(originalImagePath);
int towidth = width;
int toheight = height;
int x = 0;
int y = 0;
int ow = originalImage.Width;
int oh = originalImage.Height;
switch (mode)
{
case "HW"://指定高宽缩放（可能变形）
break;
case "W"://指定宽，高按比例
toheight = originalImage.Height * width / originalImage.Width;
break;
case "H"://指定高，宽按比例
towidth = originalImage.Width * height / originalImage.Height;
break;
case "Cut"://指定高宽裁减（不变形）
if ((double)originalImage.Width / (double)originalImage.Height > (double)towidth / (double)toheight)
{
oh = originalImage.Height;
ow = originalImage.Height * towidth / toheight;
y = 0;
x = (originalImage.Width - ow) / 2;
}
else
{
ow = originalImage.Width;
oh = originalImage.Width * height / towidth;
x = 0;
y = (originalImage.Height - oh) / 2;
}
break;
default:
break;
}
//新建一个bmp图片
System.Drawing.Image bitmap = new System.Drawing.Bitmap(towidth, toheight);
//新建一个画板
System.Drawing.Graphics g = System.Drawing.Graphics.FromImage(bitmap);
//设置高质量插值法
g.InterpolationMode = System.Drawing.Drawing2D.InterpolationMode.High;
//设置高质量,低速度呈现平滑程度
g.SmoothingMode = System.Drawing.Drawing2D.SmoothingMode.HighQuality;
//清空画布并以透明背景色填充
g.Clear(System.Drawing.Color.Transparent);
//在指定位置并且按指定大小绘制原图片的指定部分
g.DrawImage(originalImage, new System.Drawing.Rectangle(0, 0, towidth, toheight),
new System.Drawing.Rectangle(x, y, ow, oh),
System.Drawing.GraphicsUnit.Pixel);
try
{
//以jpg格式保存缩略图
bitmap.Save(thumbnailPath, System.Drawing.Imaging.ImageFormat.Jpeg);
}
catch (System.Exception e)
{
throw e;
}
finally
{
originalImage.Dispose();
bitmap.Dispose();
g.Dispose();
}
}
/**//// <summary>
/// 在图片上增加文字水印
/// </summary>
/// <param>原服务器图片路径</param>
/// <param>生成的带文字水印的图片路径</param>
protected void AddShuiYinWord(string Path, string Path_sy)
{
string addText = "测试水印";
System.Drawing.Image image = System.Drawing.Image.FromFile(Path);
System.Drawing.Graphics g = System.Drawing.Graphics.FromImage(image);
g.DrawImage(image, 0, 0, image.Width, image.Height);
System.Drawing.Font f = new System.Drawing.Font("Verdana", 16);
System.Drawing.Brush b = new System.Drawing.SolidBrush(System.Drawing.Color.Blue);
g.DrawString(addText, f, b, 15, 15);
g.Dispose();
image.Save(Path_sy);
image.Dispose();
}
/**//// <summary>
/// 在图片上生成图片水印
/// </summary>
/// <param>原服务器图片路径</param>
/// <param>生成的带图片水印的图片路径</param>
/// <param>水印图片路径</param>
protected void AddShuiYinPic(string Path, string Path_syp, string Path_sypf)
{
System.Drawing.Image image = System.Drawing.Image.FromFile(Path);
System.Drawing.Image copyImage = System.Drawing.Image.FromFile(Path_sypf);
System.Drawing.Graphics g = System.Drawing.Graphics.FromImage(image);
g.DrawImage(copyImage, new System.Drawing.Rectangle(image.Width - copyImage.Width, image.Height - copyImage.Height, copyImage.Width, copyImage.Height), 0, 0, copyImage.Width,copyImage.Height, System.Drawing.GraphicsUnit.Pixel);
g.Dispose();
image.Save(Path_syp);
image.Dispose();
}
}
