Overlaying a Bitmap image with text and lines

I've got this big HeightMap TIFF image I need to show and process in my Windows form program.

I created two controls in my GUI, one of them is an OpenGL which generates a 3D scenario from the TIFF heightmap, and the other one is a pictureBox which shows the heightmap itself.

The problem is that I need to paint some lines and text over the image in the picture box.

I read here how to effectively create a new image by combining two in an overlay fashion.

But I must not modify the image itself, othe开发者_开发技巧rwise the results in the 3D environment would be altered by these modifications. The image is huge (200MB) so cloning it and having two copies in memory would not be desirable.

Is there any way that I can over impose an image over another in the pictureBox, and only in the pictureBox, without altering the oiriginal?

I'm using Windows Forms with .NET Framework, programming language C#

Thanks in advance.