MainWindow.xaml.cs

using System.Windows;
using System.Windows.Input;
using System.Windows.Media;

namespace WPFImagePanAndZoom
{
    /// <summary>
    /// Interaction logic for MainWindow.xaml
    /// </summary>
    public partial class MainWindow : Window
    {
        private Point origin;
        private Point start;

        public MainWindow()
        {
            InitializeComponent();
            WPFWindow.MouseWheel += MainWindow_MouseWheel;

            image.MouseLeftButtonDown += image_MouseLeftButtonDown;
            image.MouseLeftButtonUp += image_MouseLeftButtonUp;
            image.MouseMove += image_MouseMove;
        }

        private void image_MouseLeftButtonUp(object sender, MouseButtonEventArgs e)
        {
            image.ReleaseMouseCapture();
        }

        private void image_MouseMove(object sender, MouseEventArgs e)
        {
            if (!image.IsMouseCaptured) return;
            Point p = e.MouseDevice.GetPosition(border);

            Matrix m = image.RenderTransform.Value;
            m.OffsetX = origin.X + (p.X - start.X);
            m.OffsetY = origin.Y + (p.Y - start.Y);

            image.RenderTransform = new MatrixTransform(m);
        }

        private void image_MouseLeftButtonDown(object sender, MouseButtonEventArgs e)
        {
            if (image.IsMouseCaptured) return;
            image.CaptureMouse();

            start = e.GetPosition(border);
            origin.X = image.RenderTransform.Value.OffsetX;
            origin.Y = image.RenderTransform.Value.OffsetY;
        }

        private void MainWindow_MouseWheel(object sender, MouseWheelEventArgs e)
        {
            Point p = e.MouseDevice.GetPosition(image);

            Matrix m = image.RenderTransform.Value;
            if (e.Delta > 0)
                m.ScaleAtPrepend(1.1, 1.1, p.X, p.Y);
            else
                m.ScaleAtPrepend(1/1.1, 1/1.1, p.X, p.Y);

            image.RenderTransform = new MatrixTransform(m);
        }
    }
}