Zooming in picturebox but with same resolution

I ha开发者_如何学编程ve a picturebox with zooming/pan capabilities. I am now starting with the zoom. I did that by:

1. getting the mousescroll event( up or down)
2. add height and width to the picturebox
3. get the pixel coordinates of mouse inside the image.

my problem is that, when i change the size of the picturebox, the pixel coordinates in the picture is not the same with the previous image without zoom. I need the coordinates to be the same even the picture is zoomed.