Methods of converting an image to graph In my thesis on object recognition based on spatial relations and visual features, I need to convert the images to graphs to be able to work on their spatial relations. Could you introduce some methods you're familiar with along with their advantages and disadvantages? Google yielded no relevant results. 

I haven't done much research yet, except for reading a few articles to get familiar with different approaches and methods and have a clear view of what I want to do. Going through this article, a method is proposed for converting an image to graph, which is called irregular pyramids. So all I want to know is whether there are other methods for such propose?
I'm not an expert, but perhaps this recent survey can help you:

K. Santle Camilus, V. K. Govindan, A Review on Graph Based Segmentation;
I.J. Image, Graphics and Signal Processing, 2012, 5, 1-13

Abstract: ... The major
four categorizations we have employed for the purpose of
review are: graph cut based methods, interactive methods,
minimum spanning tree based methods and pyramid
based methods. This review not only reveals the pros in
each method and category but also explores its
limitations. ...