title: how to do line fitting multiple lines MATLAB?
body: <p>I'm trying find all straight lines in an image which is border. for example,stamps have four edges and I have already find those edges by <code>edge</code> function in MATLAB. But there is a problem that they are not real straight line. so I need to use line fitting to get all four borders. But <code>polyfit</code> function can only fit one line at one time. Is there any solutions that can fit all lines at one time.
  for example：<a href="http://s1294.photobucket.com/user/ssjssh/library/?sort=3&amp;page=1" rel="nofollow">here</a> I upload some pictures,the image with red lines is what I want. Please be ware I need four separate lines.</p>