上传多张图片后创建缩略图的GDI +错误

Question

I've got an image upload page that works just fine when I only upload the files.

I added a 'Create Thumbnail' function. It looks like the file system has a handle on the images when the thumbnail process starts.

I get the 'unspecified GDI+ error' only when the image is over about 250K. When the files are below 250K, thumbnails are created as expected.

What are my options? Is there an elegant solution here? I want something not hacky.
Also, I am using HttpFileCollection so we can upload multiple images at one time. I've tried to use .Dispose on the Thumbnail creation, but it fails before we get to this point.

public void Upload_Click(object Sender, EventArgs e)
{
 string directory = Server.MapPath(@"~\images\");
  HttpFileCollection hfc = Request.Files;
  for (int i = 0; i < hfc.Count; i++)
  {
    HttpPostedFile hpf = hfc[i];

    if (hpf.ContentLength > 0)
    {
      string fileName = hpf.FileName;
      fileName = fileName.Replace(" ", "");
      hpf.SaveAs(fileName);
      createThumbnail(fileName);
    }
  }
}

private void createThumbnail(string filename)
{
  Image image = Image.FromFile(filename);
  Image thumb = image.GetThumbnailImage(100,100, () => false, IntPtr.Zero);
  thumb.Save(filename);
  image.Dispose();
  thumb.Dispose();
 }

Answer 1

Please let me know if this works any better:

    public string ImageDirectory { get { return Server.MapPath(@"~\images\"); } }

    public void OnUploadClick(object sender, EventArgs e)
    {
        var files = HttpContext.Request.Files.AllKeys.AsEnumerable()
            .Select(k =>HttpContext.Request.Files[k]);

        foreach(var file in files)
        {
            if(file.ContentLength <= 0)
                continue;

            string savePath = GetFullSavePath(file);
            var dimensions = new Size(100, 100);

            CreateThumbnail(file,savePath,dimensions);
        }
    }

    private void CreateThumbnail(HttpPostedFile file,string savePath, Size dimensions)
    {
        using (var image = Image.FromStream(file.InputStream))
        {
            using (var thumb = image.GetThumbnailImage(dimensions.Width, dimensions.Height, () => false, IntPtr.Zero))
            {
                thumb.Save(savePath);
            }
        }
    }

    private string GetFullSavePath(HttpPostedFile file)
    {
        string fileName = System.IO.Path.GetFileName(file.FileName).Replace(" ", "");
        string savePath = System.IO.Path.Combine(this.ImageDirectory, fileName);
        return savePath;
    }

Edit -

The foreach should have followed more to this pattern:

var files = HttpContext.Request.Files.AllKeys.AsEnumerable()
                .Select(k =>HttpContext.Request.Files[k]);

foreach(var file in files)
{

}

Answer 2

You can try this code to create your thumbnails.

       MemoryStream ms = new MemoryStream(File.ReadAllBytes(path));
       Bitmap originalBMP = new Bitmap(ms);

       int maxWidth = 200;
       int maxHeight = 200;

       // Calculate the new image dimensions 
       int origWidth = originalBMP.Width;
       int origHeight = originalBMP.Height;
       double sngRatio = Convert.ToDouble(origWidth) / Convert.ToDouble(origHeight);

       // New dimensions
       int newWidth = 0;
       int newHeight = 0;
       try
       {
           // max 200 by 200

           if ((origWidth <= maxWidth && origHeight <= maxHeight) || origWidth <= maxWidth)
           {
               newWidth = origWidth;
               newHeight = origHeight;
           }
           else
           {
               // Width longer (shrink width)
               newWidth = 200;
               newHeight = Convert.ToInt32(Convert.ToDouble(newWidth) / sngRatio);
           }

           // Create a new bitmap which will hold the previous resized bitmap 
           Bitmap newBMP = new Bitmap(originalBMP, newWidth, newHeight);
           // Create a graphic based on the new bitmap 
           Graphics oGraphics = Graphics.FromImage(newBMP);

           // Set the properties for the new graphic file 
           oGraphics.SmoothingMode = SmoothingMode.AntiAlias;
           oGraphics.InterpolationMode = InterpolationMode.High;
           // Draw the new graphic based on the resized bitmap 
           oGraphics.CompositingQuality = CompositingQuality.HighSpeed;

           oGraphics.DrawImage(originalBMP, 0, 0, newWidth, newHeight);

           // Save the new graphic file to the server 
           EncoderParameters p = new EncoderParameters(1);
           p.Param[0] = new EncoderParameter(System.Drawing.Imaging.Encoder.Compression, 70);     // Percent Compression

           MemoryStream savedBmp = new MemoryStream();

           newBMP.Save(savedBmp, ImageCodecInfo.GetImageEncoders()[1], p);

                          // Once finished with the bitmap objects, we deallocate them. 
           originalBMP.Dispose();
           newBMP.Dispose();
           oGraphics.Dispose();
           savedBmp.Dispose();

Certainly a bit more work but it does give you greater control.