convert tiff to jpeg in windows 8 RT

Question

I am trying to convert a tiff image into jpeg in windows 8 RT. I have a tiff image which contains multiple images. Now i want to convert them in separate jpeg format. I am working with a code but it is not working. it is not showing any exception but also i am not getting any thing. On debuging the code I am not getting any value in decoder variable.
 
FileOpenPicker openPicker = new FileOpenPicker();
openPicker.ViewMode = PickerViewMode.List;
openPicker.SuggestedStartLocation = PickerLocationId.ComputerFolder;
openPicker.FileTypeFilter.Add(".tif");
StorageFile image = await openPicker.PickSingleFileAsync();
 
var stream = await image.OpenAsync(Windows.Storage.FileAccessMode.Read);
var decoder = await Windows.Graphics.Imaging.BitmapDecoder.CreateAsync(stream);