package {
    import flash.display.*;
    import flash.events.*;
    import flash.net.*;
    import flash.geom.*;
    import flash.filters.*;
    
    public class @ax-actionscript-bitmap-PaletteMapDemo extends Sprite {
      private var loader:Loader;
  
      public function @ax-actionscript-bitmap-PaletteMapDemo () {
        // Load a bitmap image
        loader = new Loader();
        loader.contentLoaderInfo.addEventListener(Event.INIT, 
                                                  initListener);
        loader.load(new URLRequest("actionscript-bitmap-assets-sunset.jpg"));
      }
  
      // Invoked when the loaded image has initialized
      private function initListener (e:Event):void {
        addChild(loader.content);
        negative(Bitmap(loader.content).bitmapData);
        posterize(Bitmap(loader.content).bitmapData, 4);
      }
  
      public function negative (bitmapData:BitmapData):void {
  
        // Create the lookup tables
        var redLookupTable:Array  = new Array();
        var greenLookupTable:Array  = new Array();
        var blueLookupTable:Array  = new Array();
        for (var i:int = 0; i < 256; i++) {
          redLookupTable[i]   = (255-i) << 16;
          greenLookupTable[i] = (255-i) << 8;
          blueLookupTable[i]   = 255-i;
        }
        
        // Perform the lookup
        bitmapData.paletteMap(bitmapData, bitmapData.rect, new Point(),
                           redLookupTable, greenLookupTable, blueLookupTable);
                          
  /*
        // Faster version, using a matrix filter
        var invertFilter:ColorMatrixFilter = new ColorMatrixFilter(
                                            new Array(-1, 0, 0,0,255,
                                                       0,-1, 0,0,255,
                                                       0, 0,-1,0,255,
                                                       0, 0, 0,1,0));
        bitmapData.applyFilter(bitmapData, bitmapData.rect, 
                               new Point(0,0), invertFilter);
  */ 
                              
      }    
  
      // Uses a lookup table to posterize an image
      public function posterize (bitmapData:BitmapData,
                                 numColorsPerChannel:int):void {
        // Valid range is 1-256
        if (numColorsPerChannel < 1 || numColorsPerChannel > 256) {
          throw new Error("Number of colors per channel must be in the " + 
                          "range 1-255.");
        }
  
        // Create the lookup tables
        var redLookupTable:Array  = new Array();
        var greenLookupTable:Array  = new Array();
        var blueLookupTable:Array  = new Array();
        for (var i:int = 0; i < 256; i++) {
          redLookupTable[i] = 
                       (i-(i % Math.round(256/numColorsPerChannel))) << 16;
          greenLookupTable[i] = 
                       (i-(i % Math.round(256/numColorsPerChannel))) << 8;
          blueLookupTable[i] = 
                       (i-(i % Math.round(256/numColorsPerChannel)));
        }
  
        // Perform the lookup
        bitmapData.paletteMap(bitmapData, bitmapData.rect, new Point(),
                           redLookupTable, greenLookupTable, blueLookupTable); 
      }
  
    }
  }