title: AS3 Creating a drawing app using bitmapdata
body: <p>I'm trying to create a drawing application that renders vector lines into bitmap. I've read the documentation about bitmapdata and I have a basic understanding of how it should work. But I'm having some trouble. As of right now my goal is simple, allow the user to draw lines with their mouse, that's all I want. The problem is somewhere with the matrix i'm using, could someone help me out?</p>
  
  <pre><code>import flash.display.Sprite;              //imports needed
  import flash.events.Event;
  import flash.display.BitmapData;
  import flash.display.Bitmap;
  import flash.events.MouseEvent;
  import flash.geom.Matrix;
  
  
  
  var draw:Boolean = false;     //Boolean to determine when the mouse is down since bitmapdata doesnt receieve mouse events.
  
  var brush:Sprite =new Sprite();    // Creating the "brush", determining the stroke it will make.
  brush.graphics.lineStyle(0x000000);
  brush.graphics.lineTo(mouseX,mouseY);
  
  var data:BitmapData = new BitmapData(600,400, false); // Creating bitmapdata to allow the work with pixels.
  
  var canvas:Bitmap = new Bitmap(data);
  addChild(canvas);
  
  
  stage.addEventListener(MouseEvent.MOUSE_DOWN, drawStart);  // Event listeners to determine when the mouse is up or down.
  stage.addEventListener(MouseEvent.MOUSE_UP, drawStop);
  stage.addEventListener(Event.ENTER_FRAME, render);
  
  function drawStart(e:MouseEvent):void  // When the mouse is down we are drawing
  {
  
  
  draw= true;
  }
  
  function drawStop(e:MouseEvent):void // When the mouse is up we are not drawing
  {
  draw= false;
  }
  
  function render(e:Event):void  //Rendering the vector into bitmap
  {
  if(!draw) return;
  var mat:Matrix=new Matrix();   // We need a matrix to get the correct mouse coordinates
  mat.translate(mouseX,mouseY)
  
  
      data.draw(brush,mat);   // Then we draw the bitmap into vector.
  } 
  </code></pre>
  
  <p>I have listed comments to show what I understand is happening. If I have gotten something wrong i'd like it if someone could explain it better to me. </p>
  
  <p>When tested, the program draws lines, but all it does is draw a line to the mouse position from some other seemingly random position. So I figure the problem has something to do with the matrix.</p>
  
  <p>I appreciate any help I can get, i've been looking at this for a while and it's just not clicking. Thanks.</p>