title: CreateJs Drawing with alpha
body: <p>I implemented a little drawing function into my app with CreateJS like so:</p>
  
  <pre><code>var currentPosition = this.posOnStage(event);
  
      var drawing = container.getChildByName('drawing');
      drawing.graphics.ss(this.brushSize, "round").s(this.brushColor);
      drawing.graphics.mt(this._lastMousePosition.x, this._lastMousePosition.y);
      drawing.graphics.lt(currentPosition.x, currentPosition.y);
      drawing.alpha = this.brushAlpha;
      container.updateCache(this.enableErasing ? "destination-out" : "source-over");
      drawing.graphics.clear();
  
      this._lastMousePosition = this.posOnStage(event);
  </code></pre>
  
  <p>As you can see, the alpha value of this drawing can change. Sadly you can draw over a point you once did draw, so when you draw over a point multiple times the alpha effect will go away. Any idea how to solve this ?</p>
  
  <p>Thanks :)</p>
  
  <p>EDIT:
  <a href="https://i.stack.imgur.com/6lo05.png" rel="nofollow noreferrer"><img src="https://i.stack.imgur.com/6lo05.png" alt="enter image description here"></a></p>
  
  <p>I tried it like gskinner and  Lanny 7 proposed, but it didn't work. I attached a image so you can see the problem.</p>