fix saving scale for datasetexplorer and annotation

Azaion.Dataset/BitmapExtensions.cs

@@ -1,4 +1,5 @@
 using System.IO;
+using System.Windows;
 using System.Windows.Media.Imaging;
 
 namespace Azaion.Dataset;
@@ -16,4 +17,8 @@ public static class BitmapExtensions
         image.Freeze();
         return image;
     }
+
+    public static Size Size(this BitmapImage image) =>
+        new(image.PixelWidth, image.PixelHeight);
+
 }