本文實例講述了ASP.NET實現上傳圖片并生成縮略圖的方法。分享給大家供大家參考，具體如下：
protected void bt_upload_Click(object sender, EventArgs e){ //檢查上傳文件的格式是否有效 if (this.UploadFile.PostedFile.ContentType.ToLower().IndexOf("image") < 0) { Response.Write("上傳圖片格式無效！"); return; } //生成原圖 Byte[] oFileByte = new byte[this.UploadFile.PostedFile.ContentLength]; System.IO.Stream oStream = this.UploadFile.PostedFile.InputStream; System.Drawing.Image oImage = System.Drawing.Image.FromStream(oStream); int oWidth = oImage.Width; //原圖寬度 int oHeight = oImage.Height; //原圖高度 int tWidth = 100; //設置縮略圖初始寬度 int tHeight = 100; //設置縮略圖初始高度 //按比例計算出縮略圖的寬度和高度 if (oWidth >= oHeight) { tHeight = (int)Math.Floor(Convert.ToDouble(oHeight) * (Convert.ToDouble(tWidth) / Convert.ToDouble(oWidth))); } else { tWidth = (int)Math.Floor(Convert.ToDouble(oWidth) * (Convert.ToDouble(tHeight) / Convert.ToDouble(oHeight))); } //生成縮略原圖 Bitmap tImage = new Bitmap(tWidth, tHeight); Graphics g = Graphics.FromImage(tImage); g.InterpolationMode = System.Drawing.Drawing2D.InterpolationMode.High; //設置高質量插值法 g.SmoothingMode = System.Drawing.Drawing2D.SmoothingMode.HighQuality;//設置高質量,低速度呈現平滑程度 g.Clear(Color.Transparent); //清空畫布并以透明背景色填充 g.DrawImage(oImage, new Rectangle(0, 0, tWidth, tHeight), new Rectangle(0, 0, oWidth, oHeight), GraphicsUnit.Pixel); string oFullName = Server.MapPath(".") + "/image/" + "o" + DateTime.Now.ToShortDateString().Replace("-", "") + DateTime.Now.Hour.ToString() + DateTime.Now.Minute.ToString() + DateTime.Now.Second.ToString() + DateTime.Now.Millisecond.ToString() + ".jpg"; //保存原圖的物理路徑 string tFullName = Server.MapPath(".") + "/image/" + "t" + DateTime.Now.ToShortDateString().Replace("-", "") + DateTime.Now.Hour.ToString() + DateTime.Now.Minute.ToString() + DateTime.Now.Second.ToString() + DateTime.Now.Millisecond.ToString() + ".jpg"; //保存縮略圖的物理路徑 try { //以JPG格式保存圖片 oImage.Save(oFullName, System.Drawing.Imaging.ImageFormat.Jpeg); tImage.Save(tFullName, System.Drawing.Imaging.ImageFormat.Jpeg); } catch (Exception ex) { throw ex; } finally { //釋放資源 oImage.Dispose(); g.Dispose(); tImage.Dispose(); } }} 這里再補充一個改進方法：
#region 上傳圖片 并生成縮略圖/// <summary>/// 上傳圖片生成縮略圖/// </summary>/// <param name="originalImagePath">圖片源路徑</param>/// <param name="thumbnailPath">縮略圖路徑(物理路徑)</param>/// <param name="width">縮略圖寬度</param>/// <param name="height">縮略圖高度</param>/// <param name="mode">生成縮略圖的方式</param>public static void MakeThumbnail(string originalImagePath, string thumbnailPath, int width, int height, string mode) { //從路徑中獲取源圖片的文件 System.Drawing.Image originalImage = System.Drawing.Image.FromFile(originalImagePath); int towidth = width; int toheight = height; int x = 0; int y = 0; //獲取圖片的寬度 int ow = image.Width; //獲取圖片的高度 int oh = image.Height; //生成縮略圖的方式 switch (mode) { case "HW": break; case "W"://指定寬度 高按比例 toheight = originalImage.Height * width / originalImage.Width; break; case "H"://指定圖片的高度 寬按比例 towidth = originalImage.Width * height / originalImage.Height; break; case "Cut"://如果為裁減模式 則不變形 if ((double)originalImage.Width / (double)originalImage.Height > (double)towidth / (double)toheight) { oh = originalImage.Height; //縮略圖片的寬度 ow = originalImage.Height * towidth / toheight; y = 0; x = (originalImage.Width - ow) / 2; } else { ow = originalImage.Width; //縮略圖片的高度 oh = originalImage.Width * toheight / towidth; x = 0; y(originalImage.Height - oh) / 2; } break; default: break; } //新建一個bmp圖片 Bitmap bitmap = new Bitmap(towidth, toheight); //新建一個畫布 以BitMap 寬 高作為畫布的大小 Graphics g = Graphics.FromImage(bitmap); //設置高質量插值法 g.InterpolationMode = InterpolationMode.High; //以高質量 低速度 呈現 g.SmoothingMode = SmoothingMode.HighQuality; //清空畫布 以白色背景色填充 g.Clear(Color.Transparent); //在指定位置并且按指定大小繪制原圖片的指定部分 g.DrawImage(originalImage,new Rectangle(towidth,toheight),new Rectangle(x,y,ow,oh),GraphicsUnit.Pixel); try { //以jpg格式保存縮略圖 bitmap.Save(thumbnailPath,System.Drawing.Imaging.ImageFormat.Jpeg); } catch (Exception ex) { throw ex; } finally { //釋放資源 originalImage.Dispose(); bitmap.Dispose(); g.Dispose(); }}#endregion 希望本文所述對大家asp.net程序設計有所幫助。
