C# 生成缩略图 并下载例子源码(asp.net)

using System;using System.Collections.Generic;using System.Drawing;using System.Drawing.Imaging;using System.IO;using System.Linq;using System.Web;namespace GetminPic{ /// <summary> /// Getmin 的摘要说明 /// </summary> public class Getmin : IHttpHandler { public void ProcessRequest(HttpContext context) { //1.获取用户上传的文件流 HttpPostedFile file = context.Request.Files[0]; //获取文件名 string fileName = file.FileName; //获取扩展名 string Extension = Path.GetExtension(fileName).ToUpper(); //2.根据用户上传的文件流创建一个图片 using (Image originalImage = Image.FromStream(file.InputStream)) { //获取原始图片的宽和高 int owidth = originalImage.Width; int oheight = originalImage.Height; //缩略图的宽 int mwidth = Convert.ToInt32(context.Request.Form["width"]); //等比例的高,取整数 int mheight = mwidth * oheight / owidth; //3.根据原始图片，等比例创建一个缩小后的图片 using (Image minImage = new Bitmap(mwidth, mheight)) { //4.把大图片内容画到小图片上 //基于小图创建一个画面对象 Graphics gmin = Graphics.FromImage(minImage); //把大图画到小图上 gmin.DrawImage(originalImage, 0, 0, mwidth, mheight); //5.下载缩略图 MemoryStream ms = new MemoryStream(); //判断图片类型 ImageFormat imageFormat = null; string ContentType = ""; switch (Extension) { case ".JPG": imageFormat = ImageFormat.Jpeg; ContentType = "image/jpeg"; break; case ".PNG": imageFormat = ImageFormat.Png; ContentType = "image/png"; break; case ".GIF": imageFormat = ImageFormat.Gif; ContentType = "image/gif"; break; //................如需要其他图片格式继续添加 } minImage.Save(ms,imageFormat); context.Response.ClearContent(); context.Response.AddHeader("Content-Disposition", "attachment; filename=" HttpUtility.UrlEncode(fileName, System.Text.Encoding.UTF8)); context.Response.ContentType=ContentType; context.Response.BinaryWrite(ms.ToArray()); context.Response.End(); } } } public bool IsReusable { get { return false; } } }}