/// <summary>  /// 为图片生成缩略图    /// </summary>  /// <param name="phyPath">原图片的路径</param> /// <param name="width">缩略图宽</param>  /// <param name="height">缩略图高</param>  /// <returns></returns> public System.Drawing.Image GetThumbnail(System.Drawing.Image image, int width, intheight) { Bitmap bmp = newBitmap(width, height); //从Bitmap创建一个System.Drawing.Graphics System.Drawing.Graphics gr = System.Drawing.Graphics.FromImage(bmp); //设置  gr.SmoothingMode = System.Drawing.Drawing2D.SmoothingMode.HighQuality; //下面这个也设成高质量 gr.CompositingQuality = System.Drawing.Drawing2D.CompositingQuality.HighQuality; //下面这个设成High gr.InterpolationMode = System.Drawing.Drawing2D.InterpolationMode.HighQualityBicubic; //把原始图像绘制成上面所设置宽高的缩小图 System.Drawing.Rectangle rectDestination = newSystem.Drawing.Rectangle(0, 0, width, height); gr.DrawImage(image, rectDestination, 0, 0, image.Width, image.Height, GraphicsUnit.Pixel); returnbmp; }  

HttpPostedFile file = photoFile.PostedFile; if(!file.ContentType.Contains("image")) { return"照片格式不合法"; } stringext = Path.GetExtension(file.FileName).ToLower(); if (ext != ".jpg" && ext != ".gif" && ext != ".png"&& ext != ".jpeg") { return"请您上传jpg、gif、png图片"; } if(file.ContentLength > 5 * 1024 * 1024) { return"请您上传512字节内的图片"; } stringnewName = Guid.NewGuid().ToString(); stringtempPath = "upload/"; stringimg = tempPath + newName + ext; stringfilePath = Server.MapPath(img); if(!Directory.Exists(tempPath)) { Directory.CreateDirectory(tempPath); } using(System.Drawing.Image originalImage = System.Drawing.Image.FromStream(file.InputStream)) { GetThumbnail(originalImage, 504, 374).Save(filePath);

public void  MakeThumbnail(string originalImagePath, string thumbnailPath, int width, int height) { //获取原始图片  System.Drawing.Image originalImage = System.Drawing.Image.FromFile(originalImagePath); //缩略图画布宽高  int towidth = width; int toheight = height; //原始图片写入画布坐标和宽高(用来设置裁减溢出部分)  int x = 0; int y = 0; int ow = originalImage.Width; int oh = originalImage.Height; //原始图片画布,设置写入缩略图画布坐标和宽高(用来原始图片整体宽高缩放)  int bg_x = 0; int bg_y = 0; int bg_w = towidth; int bg_h = toheight; //倍数变量  double multiple = 0; //获取宽长的或是高长与缩略图的倍数  if (originalImage.Width >= originalImage.Height) multiple = (double)originalImage.Width / (double)width; else multiple = (double)originalImage.Height / (double)height; //上传的图片的宽和高小等于缩略图  if (ow <= width && oh <= height) { //缩略图按原始宽高  bg_w = originalImage.Width; bg_h = originalImage.Height; //空白部分用背景色填充  bg_x = Convert.ToInt32(((double)towidth - (double)ow) / 2); bg_y = Convert.ToInt32(((double)toheight - (double)oh) / 2); } //上传的图片的宽和高大于缩略图  else { //宽高按比例缩放  bg_w = Convert.ToInt32((double)originalImage.Width / multiple); bg_h = Convert.ToInt32((double)originalImage.Height / multiple); //空白部分用背景色填充  bg_y = Convert.ToInt32(((double)height - (double)bg_h) / 2); bg_x = Convert.ToInt32(((double)width - (double)bg_w) / 2); } //新建一个bmp图片,并设置缩略图大小.  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.HighQualityBilinear; //设置高质量,低速度呈现平滑程度  g.SmoothingMode = System.Drawing.Drawing2D.SmoothingMode.HighQuality; //清空画布并设置背景色  g.Clear(System.Drawing.ColorTranslator.FromHtml("#F2F2F2")); //在指定位置并且按指定大小绘制原图片的指定部分  //第一个System.Drawing.Rectangle是原图片的画布坐标和宽高,第二个是原图片写在画布上的坐标和宽高,最后一个参数是指定数值单位为像素  g.DrawImage(originalImage, new System.Drawing.Rectangle(bg_x, bg_y, bg_w, bg_h), new System.Drawing.Rectangle(x, y, ow, oh), System.Drawing.GraphicsUnit.Pixel); try { //获取图片类型  string fileExtension = System.IO.Path.GetExtension(originalImagePath).ToLower(); //按原图片类型保存缩略图片,不按原格式图片会出现模糊,锯齿等问题.  switch (fileExtension) { case ".gif": bitmap.Save(thumbnailPath, System.Drawing.Imaging.ImageFormat.Gif); break; case ".jpg": bitmap.Save(thumbnailPath, System.Drawing.Imaging.ImageFormat.Jpeg); break; case ".bmp": bitmap.Save(thumbnailPath, System.Drawing.Imaging.ImageFormat.Bmp); break; case ".png": bitmap.Save(thumbnailPath, System.Drawing.Imaging.ImageFormat.Png); break; } } catch (System.Exception e) { throw e; } finally { originalImage.Dispose(); bitmap.Dispose(); g.Dispose(); } }