Depth Map Drawing

I require someone to create a depthmap of an image. If the result is good then this is likely to lead on to other work. A depthmap is a greyscale image where the darkest parts of the image are furthest away and the lightest parts are nearest to the viewer. The depthmap should have gradient detail - i.e. it shouldn't just be a number of flat colours painted onto things at different depths - the shade must change gradually over the object in the image. Please see the attached sample for an illustration.