How to do De-Houghing of a Hough transform'ed Image?
You are  finding the coordinates of the peaks and then uses the axis to scale those into  [θ,ρ] coordinates.

Depending on how noisy the data, how many false peaks you expect and how much time you have, there are a few ways of doing it. Easiest is to pick some level that is a a real peak, cut of all data below that and then do a center of gravity on each peak to get it's center.      

You could also erode/dialte the image until each peak is a single pixel.