.NET中如何得到图片大小

        internal static void RegisterPNGImage(string name, Uri uri)
        {
            StreamResourceInfo resourceInfo = Application.GetResourceStream(uri);
            if (resourceInfo != null && resourceInfo.Stream != null)
            {
                BitmapImage image = new BitmapImage();
#if SILVERLIGHT
                image.SetSource(resourceInfo.Stream);
#else
                image.BeginInit();
                image.StreamSource = resourceInfo.Stream;
                image.EndInit();
#endif
                resourceInfo.Stream.Position = 0;
                byte[] header = new byte[8];
                resourceInfo.Stream.Read(header, 0, header.Length);
                if (header[0] == 0x89 &&
                    header[1] == 0x50 && // P
                    header[2] == 0x4E && // N
                    header[3] == 0x47 && // G
                    header[4] == 0x0D && // CR
                    header[5] == 0x0A && // LF
                    header[6] == 0x1A && // EOF
                    header[7] == 0x0A)   // LF
                {
                    byte[] buffer = new byte[16];
                    resourceInfo.Stream.Read(buffer, 0, buffer.Length);
                    Array.Reverse(buffer, 8, 4);
                    Array.Reverse(buffer, 12, 4);

                    double width = BitConverter.ToInt32(buffer, 8);
                    double height = BitConverter.ToInt32(buffer, 12);

                    resourceInfo.Stream.Close();
                    ImageUtils.RegisterImageAsset(name, new ImageAsset(image, width, height));

                    return;
                }
                resourceInfo.Stream.Close();
            }
            new Exception("Can not load PNG Image '" + name + "' URI: " + uri);
        }