WPF ItemsSource referenced StaticResource

//xaml

 <Window.Resources>
     <local:SizeConverter x:Key="sizeConverter"/>
     <local:BooksData x:Key="booksData"/>
 </Window.Resources>
 <Grid>
     <DataGrid Grid.Row="1"
               x:Name="dg"
               ItemsSource="{StaticResource booksData}"
               CanUserAddRows="False"
               AutoGenerateColumns="False"
               SelectionMode="Extended">
         <DataGrid.Columns>
             <DataGridTextColumn Header="Id" Binding="{Binding Id}"/>
             <DataGridTextColumn Header="ISBN" Binding="{Binding ISBN}"/>
             <DataGridTemplateColumn Header="Image">
                 <DataGridTemplateColumn.CellTemplate>
                     <DataTemplate>
                         <Border 
                             Width="{Binding ActualWidth,RelativeSource={RelativeSource Mode=FindAncestor,AncestorType={x:Type Window}},
                             Converter={StaticResource sizeConverter}}"
                             Height="{Binding ActualHeight,RelativeSource={RelativeSource Mode=FindAncestor,AncestorType={x:Type Window}},
                             Converter={StaticResource sizeConverter}}">
                             <Border.Background>
                                 <ImageBrush ImageSource="{Binding ImgSource}" Stretch="Uniform" />
                             </Border.Background>
                         </Border>
                     </DataTemplate>
                 </DataGridTemplateColumn.CellTemplate>
             </DataGridTemplateColumn>
         </DataGrid.Columns>
     </DataGrid>
 </Grid>

public class BooksData : ObservableCollection<Book>
{
    public BooksData()
    {
        var imgs = Directory.GetFiles(@"../../Images");
        int imgsCount = imgs.Count();
        for (int i = 0; i < 100000; i++)
        {
            this.Add(new Book()
            {
                Id = i + 1,
                ISBN = $"ISBN_{Guid.NewGuid().ToString("N")}",
                Name = $"Name_{i + 1}",
                Topic = $"Topic_{i + 1}",
                ImgUrl = $"{imgs[i % imgsCount]}",
                ImgSource = GetImageSource($"{imgs[i % imgsCount]}")
            });
        }
    }

    private ImageSource GetImageSource(string url)
    {
        BitmapImage bmi = new BitmapImage();
        bmi.BeginInit();
        bmi.UriSource = new Uri(url, UriKind.RelativeOrAbsolute);
        bmi.EndInit();
        if (bmi.CanFreeze)
        {
            bmi.Freeze();
        }
        return bmi;
    }
}


public class Book
{
    public int Id { get; set; }

    public string ISBN { get; set; }

    public string Name { get; set; }

    public string Topic { get; set; }

    public string ImgUrl { get; set; }

    public ImageSource ImgSource { get; set; }
}

 xaml

//xaml
<Window x:Class="WpfApp27.MainWindow"
        xmlns="http://schemas.microsoft.com/winfx/2006/xaml/presentation"
        xmlns:x="http://schemas.microsoft.com/winfx/2006/xaml"
        xmlns:d="http://schemas.microsoft.com/expression/blend/2008"
        xmlns:mc="http://schemas.openxmlformats.org/markup-compatibility/2006"
        WindowState="Maximized"
        xmlns:local="clr-namespace:WpfApp27"
        mc:Ignorable="d"
        Title="MainWindow" Height="450" Width="800">
    <Window.Resources>
        <local:SizeConverter x:Key="sizeConverter"/>
        <local:BooksData x:Key="booksData"/>
    </Window.Resources>
    <Grid>
        <DataGrid Grid.Row="1"
                  x:Name="dg"
                  ItemsSource="{StaticResource booksData}"
                  CanUserAddRows="False"
                  AutoGenerateColumns="False"
                  SelectionMode="Extended">
            <DataGrid.Columns>
                <DataGridTextColumn Header="Id" Binding="{Binding Id}"/>
                <DataGridTextColumn Header="ISBN" Binding="{Binding ISBN}"/>
                <DataGridTemplateColumn Header="Image">
                    <DataGridTemplateColumn.CellTemplate>
                        <DataTemplate>
                            <Border 
                                Width="{Binding ActualWidth,RelativeSource={RelativeSource Mode=FindAncestor,AncestorType={x:Type Window}},
                                Converter={StaticResource sizeConverter}}"
                                Height="{Binding ActualHeight,RelativeSource={RelativeSource Mode=FindAncestor,AncestorType={x:Type Window}},
                                Converter={StaticResource sizeConverter}}">
                                <Border.Background>
                                    <ImageBrush ImageSource="{Binding ImgSource}" Stretch="Uniform" />
                                </Border.Background>
                            </Border>
                        </DataTemplate>
                    </DataGridTemplateColumn.CellTemplate>
                </DataGridTemplateColumn>
            </DataGrid.Columns>
        </DataGrid>
    </Grid>
</Window>



using System;
using System.Collections.Generic;
using System.Collections.ObjectModel;
using System.Globalization;
using System.Linq;
using System.Text;
using System.Threading.Tasks;
using System.Windows;
using System.Windows.Controls;
using System.Windows.Data;
using System.Windows.Documents;
using System.Windows.Input;
using System.Windows.Media;
using System.Windows.Media.Imaging;
using System.Windows.Navigation;
using System.Windows.Shapes;
using System.IO;

namespace WpfApp27
{
    /// <summary>
    /// Interaction logic for MainWindow.xaml
    /// </summary>
    public partial class MainWindow : Window
    {
        public MainWindow()
        {
            InitializeComponent();
        }
    }

    public class BooksData : ObservableCollection<Book>
    {
        public BooksData()
        {
            var imgs = Directory.GetFiles(@"../../Images");
            int imgsCount = imgs.Count();
            for (int i = 0; i < 100000; i++)
            {
                this.Add(new Book()
                {
                    Id = i + 1,
                    ISBN = $"ISBN_{Guid.NewGuid().ToString("N")}",
                    Name = $"Name_{i + 1}",
                    Topic = $"Topic_{i + 1}",
                    ImgUrl = $"{imgs[i % imgsCount]}",
                    ImgSource = GetImageSource($"{imgs[i % imgsCount]}")
                });
            }
        }

        private ImageSource GetImageSource(string url)
        {
            BitmapImage bmi = new BitmapImage();
            bmi.BeginInit();
            bmi.UriSource = new Uri(url, UriKind.RelativeOrAbsolute);
            bmi.EndInit();
            if (bmi.CanFreeze)
            {
                bmi.Freeze();
            }
            return bmi;
        }
    }


    public class Book
    {
        public int Id { get; set; }

        public string ISBN { get; set; }

        public string Name { get; set; }

        public string Topic { get; set; }

        public string ImgUrl { get; set; }

        public ImageSource ImgSource { get; set; }
    }


    public class SizeConverter : IValueConverter
    {
        public object Convert(object value, Type targetType, object parameter, CultureInfo culture)
        {
            double d = 0;
            if (double.TryParse(value?.ToString(), out d))
            {
                return d / 2;
            }
            return d;
        }

        public object ConvertBack(object value, Type targetType, object parameter, CultureInfo culture)
        {
            throw new NotImplementedException();
        }
    }
}