Algorithm 1
Implementations of algorithm.
if is a color image, convert it into the gray     define as a large number to record the image difference, for example,  define as the cut step with size in , for example,  for from 0 to 1 step  // cut image  compute the convex hull of the object in image , that is,  := convexhull()  calculate the Steiner point of the object:  := CalculateSteinerPoint()  //Here, is the 2dimension Steiner point  computing image distance between two neighbor gray:   record the Steiner point corresponding to the minimum varying image gray:  if then   //Record the approximate Steiner point  end if  end for  Function CalculateSteinerpoint()  denote  for from 0 to step 1  compute the external angle of convex polygon at   end for 
