How to manipulate image on windows phone 7

So, anyway, because it seems like there is no answer, here is how i ended up doing it:

public partial class MainPage : PhoneApplicationPage
    {
        WriteableBitmap wb;
        PhotoCamera cam;

        //constructors, other stuffs...
        protected override void OnNavigatedTo(System.Windows.Navigation.NavigationEventArgs e)
                {
                    base.OnNavigatedTo(e);
                    cam = new PhotoCamera();
                    this.cam.CaptureCompleted += new EventHandler(cam_CaptureCompleted);
                    this.cam.CaptureImageAvailable += new EventHandler(cam_CaptureImageAvailable);
                }

    void cam_CaptureImageAvailable(object sender, ContentReadyEventArgs e)
        {
            Dispatcher.BeginInvoke(() => {
                BitmapImage bi = new BitmapImage();
                bi.SetSource(e.ImageStream);
                previewImage1.Source = bi;
                wb = new WriteableBitmap(ImageStack, null);
                previewImage.Source = wb;
            }); 
        }

So, basically, i put an Image object, the frames/sprites that i wanted to stack together into a grid, after the photo captured the camera, the image source will be set to that photo, and i initialized a WritableBitmap using that image stack..
of course, because of this, the resolution of the picture is limited to the resolution of the application, but well, better than nothing...