WPF rotate an image with it's base : I  want to rotate and afterwards move an image in c#. The image is in a Canvas . My problem is if you rotate the image with the following

    private void Schiff_OnMouseWheel(object sender, MouseWheelEventArgs e)
        {
            Image _schiff = (Image)sender;

            if (!_schiff.IsMouseCaptured) return;

            Matrix _mat = _schiff.RenderTransform.Value;
            Point _mouse = e.GetPosition(_schiff);

            if (e.Delta > 0)
            {
                _mat.RotateAtPrepend(22.5, _mouse.X, _mouse.Y);
            }
            else
            {
                _mat.RotateAtPrepend(-22.5, _mouse.X, _mouse.Y);
            }

            MatrixTransform _mtf = new MatrixTransform(_mat);
            _schiff.RenderTransform = _mtf;
        }

or RotateTransform

                double _angle = 0.0;

            _angle += 22.5;
            if (_angle == 360.0) _angle = 0.0;

            RotateTransform _rotate = new RotateTransform(_angle, _schiff.Width / 2, _schiff.Height / 2);

            _schiff.RenderTransform = _rotate;

you just rotate the "picture", but not it's base. So if you want to move the image with Canvas.GetLeft/GetTop, it behaves like it is still not rotated. So if you set the Top/Left-corner, the actual corner of the rotated image isn't placed where I wanted it to be. 
At https://wpf.2000things.com/2013/03/08/772-use-rendertransformorigin-to-change-center-point-for-rotation-transforms/, in the picture you can see what I mean. How can I possibly rotate the "base" with the actual image? I saw it is possible in WinForms, but (how) does it work in WPF?
Thanks in advance, if anything is unclear/wrong I will edit my question.