C# split big picture into small pieces via graphics

using System;
using System.Collections.Generic;
using System.Drawing;
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 Rectangle = System.Drawing.Rectangle;
using System.IO;

namespace WpfApp288
{
    /// <summary>
    /// Interaction logic for MainWindow.xaml
    /// </summary>
    public partial class MainWindow : Window
    {
        string path = System.IO.Path.GetDirectoryName(System.Reflection.Assembly.GetExecutingAssembly().Location);
        public MainWindow()
        {
            InitializeComponent();            
            SplitBigPicture();
        }

        private void SplitBigPicture()
        {
            string imgUrl = @"../../Images/1.jpg";
            int idx = 0;
            if (System.IO.File.Exists(imgUrl))
            {
                Bitmap bp = new Bitmap(imgUrl);
                int originalWidth = bp.Width;
                int originalHeight = bp.Height;
                int newWidth = bp.Width / 8;
                int newHeight = bp.Height / 8;
                string destDir = System.IO.Path.Combine(path, "Split8");
                if (!Directory.Exists(destDir))
                {
                    Directory.CreateDirectory(destDir);
                }
                for(int row=0;row<8;row++)
                {
                    for(int col=0;col<8;col++)
                    {
                        Bitmap newBp = new Bitmap(newWidth, newHeight);
                        using (Graphics g = Graphics.FromImage(newBp))
                        {
                            Rectangle srcRect = new System.Drawing.Rectangle(0+col*newWidth, 0+row*newHeight, newWidth,newHeight);
                            g.DrawImage(bp, 0,0, srcRect, GraphicsUnit.Pixel);
                        }
                        string newFileName = System.IO.Path.Combine(destDir, $"{row}_{col}.jpg");
                        newBp.Save(newFileName);
                    }
                }
            }
        }
    }
}