topical media & game development

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  package {
    import flash.display.*;
    import flash.ui.*;
    import flash.geom.*;
    // A basic drawing application. This version draws a vector off screen
    // and then copies that vector to a bitmap surface, thus avoiding
    // the performance degradation associated with drawing too many vectors.
    public class @ax-actionscript-scribble-ScribbleAS3_VectorV2 extends Sprite {
      private var canvas:Bitmap;;           // The on-screen bitmap canvas
      private var virtualCanvas:Shape;      // The off-screen vector canvas
      private var canvasContainer:Sprite;   // Contains the bitmap,
                                            // providing interactivity
      private var isDrawing:Boolean = false;  // Indicates whether the mouse 
                                              // is currently depressed
      private var border:Shape; // Line around the bitmap
      private var lastX:int;    // Most recently clicked x-position
      private var lastY:int;    // Most recently clicked y-position
      // Constructor
      public function @ax-actionscript-scribble-ScribbleAS3_VectorV2 () {
        // Prevent the app from resizing.
        stage.scaleMode = StageScaleMode.NO_SCALE;
      // Creates the on-screen bitmap canvas and off-screen vector canvas    
      private function createCanvas (width:int = 200, height:int = 200):void {
        // Create a new off-screen object into which individual 
        // vector lines are drawn before being copied to canvasData
        virtualCanvas = new Shape();
        // Define the data object that will store the actual pixel 
        // data for the user's drawing. Lines are copied from virtualCanvas
        // to this object.
        var canvasData:BitmapData = new BitmapData(width, 
                                                   height, false, 0xFFFFFFFF);
        // Create a new displayable Bitmap, used to render the
        // canvasData object
        canvas = new Bitmap(canvasData);
        // Create a Sprite to contain the Bitmap. The Bitmap class 
        // doesn't broadcast input events, so put it in a Sprite so the 
        // user can interact with it.
        canvasContainer = new Sprite();
        // Add the canvasContainer Sprite (and the Bitmap it contains) to
        // this object's display hierarchy
        // Put a border around the drawing surface.
        border = new Shape();;, 0, width, height);
      // Registers for the required mouse and keyboard events    
      private function registerForInputEvents ():void {
        // Register for mouse down and movement events from canvasContainer
        // Register for mouse up and key events from the Stage (i.e., 
        // globally). Use the Stage because a mouse up event should always 
        // exit drawing mode, even if it occurs while the mouse pointer is 
        // not over the drawing. Likewise, the spacebar should always clear 
        // the drawing, even when canvasContainer isn't focused. 
        stage.addEventListener(MouseEvent.MOUSE_UP, mouseUpListener);
        stage.addEventListener(KeyboardEvent.KEY_DOWN, keyDownListener);
      // Sets the color of a specified pixel. Use this for drawing a single
      // pixel because Graphics.lineTo() won't draw a single pixel
      public function drawPoint (x:int, y:int, color:uint = 0xFF000000):void {
        // Set the color of the specified pixel
        canvas.bitmapData.setPixel(x, y, color);
      // Draws a vector line in virtualCanvas, then copies that line's bitmap 
      // representation to canvasData (which is accessed via
      // canvas.bitmapData)
      public function drawLine (x1:int, y1:int, x2:int, y2:int, 
                                color:uint = 0xFF000000):void {
        // Draw line in virtualCanvas;, 0x000000, 1, true, 
                                        LineScaleMode.NORMAL, CapsStyle.NONE);, y1);, y2);
        // Copy line to canvasData 
      // Responds to MouseEvent.MOUSE_DOWN events
      private function mouseDownListener (e:MouseEvent):void {
        // Set a flag indicating that the primary 
        // mouse button is currently down
        isDrawing = true;
        // Remember the point clicked so we can draw a line to it if
        // the mouse moves
        lastX = e.localX;
        lastY = e.localY;
        // Draw a dot where the mouse was clicked
        drawPoint(e.localX, e.localY);
      // Responds to MouseEvent.MOUSE_MOVE events
      private function mouseMoveListener (e:MouseEvent):void {
        // Draw a line when the mouse moves over the drawing
        // while the primary mouse button is depressed
        if (isDrawing) {
          // Use localX and localY to obtain pointer position relative to 
          // the canvasContainer.
          var thisX:int = e.localX;
          var thisY:int = e.localY;
          // Draw a line to the new mouse location
          drawLine(lastX, lastY, thisX, thisY);
          // Remember the last mouse position for next time
          lastX = thisX;
          lastY = thisY;
          // Update the screen immediately following the execution of
          // this event listener function
      // Responds to MouseEvent.MOUSE_UP events    
      private function mouseUpListener (e:MouseEvent):void {
        // Set a flag indicating that the primary mouse button is currently up
        isDrawing = false;
      // Responds to KeyboardEvent.KEY_DOWN events
      private function keyDownListener (e:KeyboardEvent):void {
        // Clear the drawing when the spacebar is pressed. To clear the
        // drawing, we set all pixels to the color white.
        if (e.charCode == Keyboard.SPACE) {
          canvas.bitmapData.fillRect(new Rectangle(0, 0, 
                                                 canvas.width, canvas.height),

(C) Æliens 27/08/2009

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