title: Choosing isolines from Matlab contour function
body: <p>The Matlab contour function (and imcontour) plots isolines of different levels of a matrix.
  I would like to know: How can I manipulate the output of this function in order to receive all the (x,y) coordinates of each contour, along with the level? 
  How can I use the output [C,h] = contour(...)  to achieve the aforementioned task? Also, I am not interested in manipulating the underlying grid, which is a continuous function, <strong>only extracting the relevant pixels which I see on the plot</strong>. </p>