nesting(function(calls()))

By Zevan | January 17, 2009
CLICK HERE TO COPY
Actionscript:
  1. [SWF(width=500, height=500, backgroundColor=0x000000, frameRate=30)]
  2.  
  3. for (var i:int = 0; i<10; i++){
  4.        // draggable ellipse
  5.     var dot:Sprite = drag(createSprite("Ellipse",  -10, -10, 20, 20));
  6.     dot.x = Math.random() * stage.stageWidth ;
  7.     dot.y = Math.random() * stage.stageHeight ;
  8. }
  9.  
  10. for (i = 0; i<10; i++){
  11.  
  12.       var box:Sprite = drag(spin(createSprite("Rect", -20, -20, 40, 40, 0xFF0000), Math.random()*5 + 1));
  13.     box.x = Math.random() * stage.stageWidth ;
  14.     box.y = Math.random() * stage.stageHeight ;
  15. }
  16.  
  17.  
  18.  // createSprite can create ellipses or rectangles
  19. function createSprite(shape:String, xp:Number, yp:Number, w:Number, h:Number, col:uint=0x444444):Sprite {
  20.     var s:Sprite = new Sprite();
  21.     s.graphics.beginFill(col);
  22.     // trick from a previous post
  23.     s.graphics["draw" + shape](xp, yp, w, h);
  24.     addChild(s);
  25.     return s;
  26. }
  27.  
  28. // drag and spin add listeners to an untyped target and return that target for easy function nesting
  29. function drag(target:*):*{
  30.     target.addEventListener(MouseEvent.MOUSE_DOWN, function(evt:MouseEvent){ evt.currentTarget.startDrag(); });
  31.     return target;
  32. }
  33.  
  34. function spin(target:*, speed:Number):*{
  35.     target.addEventListener(Event.ENTER_FRAME, function(evt:Event){ evt.currentTarget.rotation+=speed; });
  36.     return target;
  37. }
  38.  
  39. stage.addEventListener(MouseEvent.MOUSE_UP, function(){ stopDrag() });

The above will create some draggable circles and some rotating draggable rects... but that's not really the point....

When prototyping and just playing around I write functions that take an Object as an argument, alter that Object in some way and pass that some Object out as a return value.... this makes it so I can write things like this:

CLICK HERE TO COPY
Actionscript:
  1. drag(spin(createSprite("Rect", -20, -20, 40, 40, 0xFF0000), Math.random()*5 + 1));

Readability can be a problem so... consider that before using this for anything...

Posted in dynamic, functions, misc | Tagged , | Leave a comment

Image Airbrush

By Zevan | January 16, 2009
CLICK HERE TO COPY
Actionscript:
  1. [SWF(width=500, height=500, backgroundColor=0x000000, frameRate=30)]
  2.  
  3. // draw an ugly gradient
  4. var size:int = 500;
  5. var pixNum:int = size * size;
  6. var gradient:BitmapData = new BitmapData(size, size, true, 0xFF000000);
  7.  
  8. gradient.lock();
  9. var xp:int, yp:int;
  10. for (var i:int = 0; i<pixNum; i++){
  11.     xp = i % size;
  12.     yp = i / size;
  13.     gradient.setPixel(xp, yp, (yp /= 2) <<16 | (255 - yp) <<8 | (xp / 2) );
  14. }
  15. gradient.unlock();
  16.  
  17. // draw an alphaChannel (radial gradient)
  18. var radius:Number = 50;
  19. var diameter:Number = radius * 2;
  20.  
  21. pixNum = diameter * diameter;
  22.  
  23. var brushAlpha = new BitmapData(diameter, diameter, true, 0x00000000);
  24. var dx:int, dy:int;
  25. var ratio:Number = 255 / radius;
  26. var a:int;
  27.  
  28. brushAlpha.lock();
  29. for (i = 0; i<pixNum; i++){
  30.     xp = i % diameter;
  31.     yp = i / diameter;
  32.     dx = xp - radius;
  33.     dy = yp - radius;
  34.     a = int(255 - Math.min(255,Math.sqrt(dx * dx + dy * dy) * ratio));
  35.     brushAlpha.setPixel32(xp, yp, a <<24);
  36. }
  37. brushAlpha.unlock();
  38.  
  39. // create a black canvas
  40. var canvas:BitmapData = new BitmapData(size, size, true, 0xFF000000);
  41. addChild(new Bitmap(canvas));
  42.  
  43. addEventListener(Event.ENTER_FRAME, onLoop);
  44. function onLoop(evt:Event):void {
  45.     // draw the gradient onto the canvas using the alphaChannel (brushAlpha);
  46.     xp = mouseX - radius;
  47.     yp = mouseY - radius;
  48.     canvas.copyPixels(gradient,
  49.                     new Rectangle(xp, yp, diameter, diameter),
  50.                     new Point(xp, yp), brushAlpha, new Point(0,0), true);
  51. }

This demo creates an airbrush that paints one BitmapData onto another. This is achieved by using the alpha related arguments of the BitmapData.copyPixels() function. If your not familiar with these you should take some time to play around with them... they're very powerful.

copyPixels() is the fastest way to draw in flash, so if you need speed, copyPixels() is the way to go. It's much faster than using draw().

Posted in BitmapData, setPixel | Tagged , | 2 Comments

Script List Pattern

By Zevan | January 15, 2009
CLICK HERE TO COPY
Actionscript:
  1. var currentState:String = "";
  2.  
  3. var functionList:Vector.<Function> = new Vector.<Function>();
  4.  
  5. function clearFunctions():void{
  6.     functionList = new Vector.<Function>();
  7. }
  8. function addFunction(f:Function):Function {
  9.     functionList.push(f);
  10.     return addFunction;
  11. }
  12.  
  13. function removeFunction(f:Function):void {
  14.     for (var i:int = 0 ; i<functionList.length; i++){
  15.         if (f == functionList[i]){
  16.             functionList.splice(i, 1);
  17.         }
  18.     }
  19. }
  20.  
  21. function runProgram():void {
  22.    
  23.     currentState = "current: ";
  24.    
  25.     for (var i:int = 0; i<functionList.length; i++){
  26.         functionList[i]();
  27.     }
  28.    
  29.     trace(currentState);
  30. }
  31.  
  32. function one():void{
  33.     currentState += " one";
  34. }
  35.  
  36. function two():void {
  37.     currentState += " two";
  38. }
  39.  
  40. function three():void {
  41.     currentState += " three";
  42. }
  43.  
  44. function dot():void{
  45.     currentState += ".";
  46.    
  47. }
  48.  
  49. // test it:
  50. addFunction(one);
  51. addFunction(two);
  52. addFunction(three);
  53.  
  54. runProgram();
  55.  
  56. removeFunction(one);
  57.  
  58. runProgram();
  59.  
  60. addFunction(dot)(dot)(dot);
  61.  
  62. runProgram();
  63.  
  64. clearFunctions();
  65.  
  66. addFunction(dot)(dot)(dot);
  67.  
  68. addFunction(three)(two)(one)(dot)(dot)(dot);
  69.  
  70. runProgram();
  71.  
  72. /* outputs:
  73. current:  one two three
  74. current:  two three
  75. current:  two three...
  76. current: ... three two one...
  77. */

This is a very quick implementation of a pattern that I use sometimes. The idea of this pattern is very simple and can easily be implemented in OOP or procedural style programming. The idea is to have a Vector/Array of functions or Class instances. Loop through this Vector/Array and run each function (or a given method of each Class instance). During runtime your client code can alter this list to change what the program does.

I use this technique for games quite often. All enemies get added to an enemy list - this list is looped through and each enemies run() method is called. If an enemy dies it dispatches an event that tells the enemy manager to remove it from the list. Some pseudo code:

CLICK HERE TO COPY
Actionscript:
  1. function onMainLoop():void{
  2.     if (!paused){
  3.        
  4.         runWorld();
  5.         runKeys();
  6.         runChar();
  7.        
  8.         enemyManager.runEnemies();
  9.        
  10.         runPickups();
  11.        
  12.     }else{
  13.         // show pause screen
  14.     }
  15. }
  16.  
  17. //... inside EnemyManager class
  18. function onRunEnemies():void{
  19.     for (var i:int = 0; i<enemyList.length; i++){
  20.             enemyList[i].run(i);
  21.     }
  22. }

I use the same technique for pickups (coins, lives etc....).

I first used this technique in Director with a list of parent scripts.

I'm aware of other more refined patterns that are meant to do similar things, but for small to medium sized apps this has worked very nicely for me.

Posted in Vector, arrays, misc | Tagged , | 2 Comments

BitmapData lock() & unlock()

By Zevan | January 15, 2009
CLICK HERE TO COPY
Actionscript:
  1. var size:Number = 400;
  2. var pixelNum:Number = size * size;
  3. var pixels:Vector.<uint> = new Vector.<uint>();
  4. var r:uint;
  5. var g:uint;
  6. var b:uint;
  7.  
  8. var canvas:BitmapData = new BitmapData(size,size,false,0x000000);
  9. addChild(new Bitmap(canvas));
  10.  
  11. addEventListener(Event.ENTER_FRAME, onLoop);
  12. function onLoop(evt:Event):void {
  13.  
  14.     canvas.lock();
  15.  
  16.     // do any kind of pixel manipulation here:
  17.    
  18.     for (var i:int = 0; i<pixelNum; i++) {
  19.         // draw a gradient that changes based on
  20.         // mouse position
  21.         r = i % size + mouseX;
  22.         b = i / size + mouseY;
  23.         g = (r + b) % mouseX;
  24.         pixels[i] = r <<16 | g <<8 | b;
  25.     }
  26.     canvas.setVector(canvas.rect, pixels);
  27.     //
  28.  
  29.     canvas.unlock();
  30. }

Using BitmapData.lock() and BitmapData.unlock() can speed up BitmaData drawing operations significantly. Simply lock your BitmapData before you draw to it, and unlock it when your done.

I often forget to do this until I get to the optimize phase of a project... but I think I'd like to get in the habit of doing it all the time....

Posted in BitmapData, pixel manipulation | Tagged , | 2 Comments