我在处理多帧的tiff文件,但是有几帧是JPEG压缩格式。结果，当我欲使用BitmapFrame类（表示由解码器返回并被编码器接受的图像数据）处理时，在执行BitmapFrame.Create(bitmapSource)时出错。部分代码如下：
//code
Stream imageStreamSource = new FileStream(source, FileMode.Open, FileAccess.Read, FileShare.Read);
                TiffBitmapDecoder decoder = new TiffBitmapDecoder(imageStreamSource, BitmapCreateOptions.None, BitmapCacheOption.Default);
                int i = 0;
                foreach (BitmapSource bitmapSource in decoder.Frames)
                {
                    i++;
                    string filename = dest + "_" + i.ToString() + ".png";
                    xpsImages.Add(filename);
                    xpsImagesSize.Add(new Size((int)bitmapSource.Width, (int)bitmapSource.Height));
                    FileStream stream = new FileStream(filename, FileMode.Create);
                    PngBitmapEncoder encoder = new PngBitmapEncoder();
                    encoder.Interlace = PngInterlaceOption.On;
                    encoder.Frames.Add(BitmapFrame.Create(bitmapSource));
                    encoder.Save(stream);
                    stream.Close();
                }
                imageStreamSource.Close();
//code
请问为什么会如此呢？如何在C#里处理经JPEG压缩的TIFF文件？恳请各位高手指教！