上传图片的缩略图创建

Question

我想上传多张图像并将其保存到我的应用程序中的一个文件夹中，并将相同图像的缩略图保存在一个名为 Thumbnail 的文件夹中。我成功地将图像上传并保存在图像文件夹中。我也想保存它的缩略图。

在视图中

<form action="" method="post" enctype="multipart/form-data">
  @Html.Label("Select the property : ");
  @Html.DropDownList("Address", new SelectList(ViewBag.Address as System.Collections.IEnumerable), "---Select---",new { id = "add"})
  <label for="file">Filename:</label>
  <input type="file" name="files" id="file" multiple="true"/>

  <input type="submit" />

在控制器中

public class HomeController : Controller
    {
        PropertyAssessmentSystemEntities db = new PropertyAssessmentSystemEntities();

        public ActionResult Index()
        {
            var q = from pi in db.PropertyInfoes
                    select pi.Full_Address;
            ViewBag.Address = q.ToList();
            return View();
        }

        [HttpPost]
        public ActionResult Index(HttpPostedFileBase[] files,FormCollection c)
        {
            int no = 0,no1 =0;
            string path = Path.Combine(Server.MapPath("~/Images"), c["Address"].Replace(' ', '_'));
            string fn = "", fn1 = "";
            if (!Directory.Exists(path))
                Directory.CreateDirectory(path);
            else
                no = Directory.GetFiles(path).Length;
            foreach (var file in files)
            {
                string fname = "img_" + no++ + file.FileName.Substring(file.FileName.LastIndexOf('.'));
                string fname1 = "img_" + no1++ + file.FileName.Substring(file.FileName.LastIndexOf('.'));
                fname1 = Path.Combine("Thumbnail", fname1);
                fn1 = Path.Combine(path, fname1);
                if (!Directory.Exists(fn1))
                    Directory.CreateDirectory(fn1);
                else
                    no = Directory.GetFiles(fn1).Length;

                fn = Path.Combine(path, fname);
                file.SaveAs(fn);
                Stream strm = new FileStream(fn, FileMode.OpenOrCreate);
                GenerateThumbnails(0.05, strm, fn1);
            }

            return RedirectToAction("Index");
        }

        private void GenerateThumbnails(double scaleFactor, Stream sourcePath, string targetPath)
        {
            using (var image = System.Drawing.Image.FromStream(sourcePath))
            {
                var newWidth = (int)(image.Width * scaleFactor);
                var newHeight = (int)(image.Height * scaleFactor);
                var thumbnailImg = new Bitmap(newWidth, newHeight);
                var thumbGraph = Graphics.FromImage(thumbnailImg);
                thumbGraph.CompositingQuality = CompositingQuality.HighQuality;
                thumbGraph.SmoothingMode = SmoothingMode.HighQuality;
                thumbGraph.InterpolationMode = InterpolationMode.HighQualityBicubic;
                var imageRectangle = new Rectangle(0, 0, newWidth, newHeight);
                thumbGraph.DrawImage(image, imageRectangle);
                thumbnailImg.Save(targetPath,image.RawFormat);
            } }}

---

执行此操作时，thumbnailImg.Save(targetPath,image.RawFormat); 中发生错误 GDI+ 中出现一般错误。谁能帮我解决这个问题？？

Answer 1

我有另一种在上传时从图像创建缩略图的方法，如下所示：

在您的 using 命名空间中添加以下指令：

using System.Drawing;
using System.Drawing.Imaging;

在您的控制器操作中添加以下代码以创建缩略图

using (var image = Image.FromStream(file.InputStream, true, true)) /* Creates Image from specified data stream */
{
     using (var thumb = image.GetThumbnailImage(
          36, /* width*/
          30, /* height*/
          () => false,
          IntPtr.Zero))
       {
          var jpgInfo = ImageCodecInfo.GetImageEncoders().Where(codecInfo => codecInfo.MimeType == "image/png").First(); /* Returns array of image encoder objects built into GDI+ */
          using (var encParams = new EncoderParameters(1))
          {
              var appDataThumbnailPath = Server.MapPath("~/Uploads/Thumbnail/" + User.id);
              if (!Directory.Exists(appDataThumbnailPath))
              {
                  Directory.CreateDirectory(appDataThumbnailPath);
              }
              string outputPath = Path.Combine(appDataThumbnailPath, fileName);
              long quality = 100;
              encParams.Param[0] = new EncoderParameter(Encoder.Quality, quality);
              thumb.Save(outputPath, jpgInfo, encParams);
          }
       }
 }

这里的 file 是具有输入图像的 HttpPostedFileBase 对象，outputPath 是缩略图的目标文件。通过以下过程，您将获得缩略图。