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 id="form1" runat="server"> <div> <asp:FileUpload ID="FileUpload1" runat="server" /> <asp:Button ID="Button1" runat="server" OnClick="Button1_Click" Text="上传" /><br /> <asp:Label ID="Label1" 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); // 使用 SaveAs 方法保存文件 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 name="originalImagePath">源图路径（物理路径）</param> /// <param name="thumbnailPath">缩略图路径（物理路径）</param> /// <param name="width">缩略图宽度</param> /// <param name="height">缩略图高度</param> /// <param name="mode">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 name="Path">原服务器图片路径</param> /// <param name="Path_sy">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 name="Path">原服务器图片路径</param> /// <param name="Path_syp">生成的带图片水印的图片路径</param> /// <param name="Path_sypf">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(); }
}