title: matlab image processing- line passing through 2 points extending beyond the x1,y1 coordinate
body: <p>I have a problem to solve in matlab. I have 2 points A[x1,x2] and B[y1,y2] of my particles in Image. i want to plot a line between the 2 points and extend it beyond the x1,y1 coordinate alone. </p>
  
  <p>i later check where it intersects.This will tell me where the particle originates. 
  is there some simple code for this? </p>
  
  <p>thank you</p>
  
  <p>regards</p>
  
  <p>Avinash</p>