在线生成缩略图

/// <summary> /// 获取截图 /// </summary> /// <param name="sender"></param> /// <param name="e"></param> protected void btnGo_Click(object sender, EventArgs e) { HttpWebRequest myReq = (HttpWebRequest)HttpWebRequest.Create(txtAddress.Text); HttpWebResponse HttpWResp = (HttpWebResponse)myReq.GetResponse(); Stream myStream = HttpWResp.GetResponseStream(); System.Drawing.Image oImage = System.Drawing.Image.FromStream(myStream); string fileName = DateTime.Now.Year.ToString() + DateTime.Now.Second.ToString() + ".jpg"; oImage.Save(Server.MapPath("upFiles/" + fileName), System.Drawing.Imaging.ImageFormat.Gif); string webFilePath = Server.MapPath(txtAddress.Text); string webFilePath_s = Server.MapPath("smallFiles/" + fileName); MakeThumbnail(webFilePath, webFilePath_s, 400, 200, "W"); } /// <summary> /// 设置裁剪图片 /// </summary> /// <param name="originalImagePath">图片地址</param> /// <param name="thumbnailPath">物理地址</param> /// <param name="width"></param> /// <param name="height"></param> /// <param name="mode"></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; } 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 { using (MemoryStream ms = new MemoryStream()) { } //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(); } } ｝