title: get tangent line on particular point of curve?
body: <p>My Idea or Project:</p>
  
  <p>I want to develop an application which takes an image as input and returns another image as output.
  For example: I have a bitmap image with a circle drawn inside it. What i want to develop is an algorithm that will draw another circle inside it. I know this is rather easy but it should work for any kind of starting image like a triangle or any other shape.</p>
  
  <p>According to me, I have to go through the shape's inside-periphery and draw a line. 
  However, I am having problems with dynamic shapes. The problem is easy for circles, elipses and rectangles as we know the algorithm but becomes hard for any other shape.</p>
  
  <p>Any thoughts as to how I can achieve this? If I can get tangent line on a particular  point of  the curve then I could also do what I need. </p>