Another Screensaver with WPF

using System;
using System.Diagnostics;
using System.Windows;
using System.Windows.Controls;
using System.Windows.Media;
using System.Windows.Media.Imaging;

namespace RZWScreenSaver.SlidePages{
    /// <summary>
    /// Interaction logic for SlidePage.xaml
    /// </summary>
    public class SlidePage : Page, ISlidePage {
        #region Implementation of ISlidePage

        public DisplayMode DisplayMode{
            get { return displayMode; }
            set{
                if (displayMode != value){
                    displayMode = value;
                    OnDisplayModeChanged();
                }
            }
        }
        public virtual bool ShowTitle{
            get { return false; }
            set { }
        }
        void ISlidePage.OnPictureSetChanged(object sender, EventArgs arg){
            OnPictureSetChanged(sender, arg);
        }
        void ISlidePage.OnShowPicture(object sender, PictureChangedEventArgs arg){
            OnShowPicture(sender, arg);
        }

        #endregion
        protected virtual void OnDisplayModeChanged(){}
        protected virtual void OnPictureSetChanged(object sender, EventArgs arg){}
        protected virtual void OnShowPicture(object sender, PictureChangedEventArgs arg){}

        static protected string FormatImageDescription(ImageSource image, string path, DateTime fileDate, int? orientation){
            if (orientation == null || orientation.Value == 0)
                return string.Format("[{0}x{1}] {2} {3}", image.Width.ToString("F0"),
                                     image.Height.ToString("F0"),
                                     fileDate.ToString("G"), path);
            else
                return string.Format("[{0}x{1} {2}\u00B0] {3} {4}",
                    image.Width.ToString("F0"),image.Height.ToString("F0"),
                    orientation,
                    fileDate.ToString("G"), path);
        }
        static protected int? GetImageOrientation(ImageSource image){
            const string exifOrientation = "System.Photo.Orientation";
            var bitmapMeta = image.Metadata as BitmapMetadata;
            if (bitmapMeta == null || !bitmapMeta.ContainsQuery(exifOrientation))
                return null;
            var orientation = Convert.ToInt32(bitmapMeta.GetQuery(exifOrientation));
            // refer to http://www.impulseadventure.com/photo/exif-orientation.html
            // all mirror cases are treated as normal cases.
            switch (orientation){
            case 1:
            case 2: // mirror
                return 0;
            case 7: // mirror
            case 8:
                return 90 /* degree clockwise */;
            case 3:
            case 4: // mirror
                return 180 /* degree clockwise */;
            case 5: // mirror
            case 6:
                return 270 /* degree clockwise */;
            default:
                Trace.WriteLine("Unrecognized EXIF orientation: " + orientation.ToString());
                return null;
            }
        }
        static protected void GetImageSizeByOrientation(ImageSource image, int? orientation, out Size imageSize){
            imageSize = IsLandscape(orientation) ? new Size(image.Width, image.Height) : new Size(image.Height, image.Width);
        }
        static protected bool IsLandscape(int? orientation){
            return orientation == null || orientation.Value == 0 || orientation.Value == 180;
        }

        DisplayMode displayMode = DisplayMode.Fit;
    }
}