GDI+: How can I get translate, scale and rotate transforms working together?

[VicJ]

I'm trying to make a control on which the user can freely drag an image with the mouse and zoom and rotate it with the mouse wheel. I'd like to do this as far as possible using graphics transforms. At the moment, I have the code below in the Paint event handler of a Windows Form. The variables PanOrigin (Point), ZoomFactor (Single, starting value 1.0) and RotateDegrees (Integer) are controlled by mouse actions; I trust their meanings are obvious. The point mp is the centre of the window.

e.Graphics.TranslateTransform(-mp.X, -mp.Y, MatrixOrder.Append)
e.Graphics.RotateTransform(RotateDegrees, MatrixOrder.Append)
e.Graphics.ScaleTransform(ZoomFactor, ZoomFactor, MatrixOrder.Append)
e.Graphics.TranslateTransform(PanOrigin.X, PanOrigin.Y, MatrixOrder.Append)
e.Graphics.TranslateTransform(mp.X, mp.Y, Drawing2D.MatrixOrder.Append)
e.Graphics.DrawImage(TestImage, 0, 0)
 

The problem with this is that the effective centre of rotation and zooming moves along with the image, instead of staying at the window centre. I've tried modifying the above code with the TransformPoints method (see lines 4-6):

e.Graphics.TranslateTransform(-mp.X, -mp.Y, MatrixOrder.Append)
e.Graphics.RotateTransform(RotateDegrees, MatrixOrder.Append)
e.Graphics.ScaleTransform(ZoomFactor, ZoomFactor, 
Dim pts() as Point={PanOrigin}
e.Graphics.TransformPoints(CoordinateSpace.Device, CoordinateSpace.World, pts)
e.Graphics.TranslateTransform(pts(0).X, pts(0).Y, MatrixOrder.Append)
e.Graphics.TranslateTransform(mp.X, mp.Y, Drawing2D.MatrixOrder.Append)
e.Graphics.DrawImage(TestImage, 0, 0)
 

Now zooming and rotating stay centred at the middle of the window as intended, but dragging the image takes it off in a direction of its own instead of the dragged direction.

I have tried all kinds of adjustments and variations but so far I have not succeeded in getting rid of both these problems at the same time. Surely there must be a way. I hope someone on this forum can help me: replies in C# are also gratefully accepted (if not too long or complex!).

Regards, Vic