title: Actionscript: Make a mask follow a line (and "grow")
body: <p>does anybody know/have some idea how to make a mask follow a line? Basically I have a drawing made with 1px line and I need to gradually mask this shape so it actually looks like it is being drawn. The thing is that I cannot just increase the width of the mask (it would simple draw a vertical line in one step which is not desired), it has to be a linear movement along the "guide" line, so the vertical line gets drawn in several steps. Doing this manually will/would be a major pain. This is what I am trying to achieve:
  <img src="https://i.stack.imgur.com/3O1IZ.png" alt="Example of the drawing"></p>
  
  <p>Thanks a lot!</p>