Why does this thumbnail generation code throw OutOfMemoryException on large files?

This code works great for generating thumbnails, but when given a very large (100MB+) TIFF file, it throws OutOfMemoryExceptions. When I do it manually in Paint.NET on the same machine, it works fine. How can I improve this code to stop throwing on very large files?

In this case I'm loading a 721MB TIF on a machine with 8GB RAM. The Task Manager shows 2GB used so something is preventing it from using all that memory. Specifically it throws when I load the Image to calculate the size of the original. What gives?

/// <summary>Creates a thumbnail of a given image.</summary>
/// <param name="inFile">Fully qualified path to file to create a thumbnail of</param>
/// <param name="outFile">Fully qualified path to created thumbnail</param>
/// <param name="x">Width of thumbnail</param>
/// <returns>flag; result = is success</returns>
public static bool CreateThumbnail(string inFile, string outFile, int x)
{
  // Mathematically determine Y dimension
  int y;
  using (Image img = Image.FromFile(inFile)) // Exception thrown
      y = (int)((double)img.Height * ((double)x / (double)img.Width));

  // Make thumbnail     
  using (Bitmap bmp = new Bitmap(inFile)) 
    using (Bitmap thumb = new Bitmap((Image)bmp, new Size(x, y))) 
      using (Graphics g = Graphics.FromImage(thumb)) {
        g.SmoothingMode = SmoothingMode.HighQuality;
        g.InterpolationMode = InterpolationMode.High;
        g.CompositingQuality = CompositingQuality.HighQuality;
        ImageCodecInfo codec = ImageCodecInfo.GetImageEncoders()[1];
        EncoderParameters ep2 = new EncoderParameters(1);
        ep2.Param[0] = new EncoderParameter(Encoder.Quality, 100L);
        g.DrawImage(bmp, new Rectangle开发者_如何转开发(0,0,thumb.Width, thumb.Height));
        try {
          thumb.Save(outFile, codec, ep2);
          return true; }
        catch { return false; }
      }
}

My wild guess is that, you are running it as a 32-bit application. Which limits your app's memory usage to a theoretical 2 GB, which is really more like 1.5 GB empirically.

Have you tried with FastImageGDIPlus. It has worked well for me - but I've never tried loading a 721 MB file.