net/systemeD/halcyon/TileSet.as

   1 package net.systemeD.halcyon {
   2
   3         // ** Need to support different zoom levels
   4         //    When zoom level changes:
   5         //              - double or halve xoffset/yoffset accordingly
   6         //              - blank the tile queue
   7
   8         import flash.display.*;
   9         import flash.events.*;
  10         import flash.net.*;
  11
  12         import net.systemeD.halcyon.ImageURLLoader;
  13         import net.systemeD.halcyon.Globals;
  14         import flash.system.LoaderContext;
  15
  16     public class TileSet extends Sprite {
  17
  18                 public var baseurl:String;
  19
  20                 public var tile_l:int;
  21                 public var tile_r:int;
  22                 public var tile_b:int;
  23                 public var tile_t:int;
  24
  25                 public var xoffset:Number=0;
  26                 public var yoffset:Number=0;
  27
  28                 private var requests:Array=[];
  29                 private var tiles:Object={};            // key is "z,x,y"; value "true" (needed) or reference to sprite
  30                 private var waiting:int=0;                      // number of tiles currently being downloaded
  31
  32                 private var map:Map;
  33
  34
  35         public function TileSet(map:Map) {
  36                         this.map=map;
  37                 }
  38
  39                 public function init(url:String):void {
  40                 }
  41
  42                 // Update bounds - called on every move
  43
  44                 public function update():void {
  45                         tile_l=lon2tile(map.edge_l+xoffset);
  46                         tile_r=lon2tile(map.edge_r+xoffset);
  47                         tile_t=lat2tile(map.edge_t+yoffset);
  48                         tile_b=lat2tile(map.edge_b+yoffset);
  49                         for (var tx:int=tile_l; tx<=tile_r; tx++) {
  50                                 for (var ty:int=tile_t; ty<=tile_b; ty++) {
  51                                         if (!tiles[map.scale+','+tx+','+ty]) { addRequest(tx,ty); }
  52                                 }
  53                         }
  54                 }
  55
  56                 // Mark that a tile needs to be loaded
  57
  58                 public function addRequest(tx:int,ty:int):void {
  59                         tiles[map.scale+','+tx+','+ty]=true;
  60                         requests.push([map.scale,tx,ty]);
  61                 }
  62
  63                 // Service tile queue - called on every frame to download new tiles
  64
  65                 public function serviceQueue():void {
  66                         if (waiting==4 || requests.length==0) { return; }
  67                         var r:Array, tx:int, ty:int, tz:int;
  68
  69                         for (var i:uint=0; i<Math.min(requests.length, 4-waiting); i++) {
  70                                 r=requests.shift(); tz=r[0]; tx=r[1]; ty=r[2];
  71                                 if (tx>=tile_l && tx<=tile_r && ty>=tile_t && ty<=tile_b) {
  72                                         // Tile is on-screen, so load
  73                                         var loader:Loader = new Loader();
  74                                         loader.contentLoaderInfo.addEventListener(Event.INIT, doImgInit);
  75                                         loader.load(new URLRequest(tileURL(tx,ty)),
  76                                                     new LoaderContext(true));
  77                                         this.addChild(loader);
  78                                         loader.x=map.lon2coord(tile2lon(tx));
  79                                         loader.y=map.lat2coord(tile2lat(ty));
  80                                         loader.alpha=0.5;
  81                                 }
  82                         }
  83                 }
  84
  85                 protected function doImgInit(evt:Event):void {
  86                         waiting--;
  87                         return;
  88                 }
  89
  90
  91                 // Assemble tile URL
  92
  93                 private function tileURL(tx:int,ty:int):String {
  94                         return "http://npe.openstreetmap.org/"+map.scale+"/"+tx+"/"+ty+".png";
  95 //                      return "http://andy.sandbox.cloudmade.com/tiles/cycle/"+map.scale+"/"+tx+"/"+ty+".png";
  96                 }
  97
  98
  99
 100                 // ------------------------------------------------------------------
 101                 // Co-ordinate conversion functions
 102
 103                 private function lon2tile(lon:Number):int {
 104                         return (Math.floor((lon+180)/360*Math.pow(2,map.scale)));
 105                 }
 106                 private function lat2tile(lat:Number):int {
 107                         return (Math.floor((1-Math.log(Math.tan(lat*Math.PI/180) + 1/Math.cos(lat*Math.PI/180))/Math.PI)/2 *Math.pow(2,map.scale)));
 108                 }
 109                 private function tile2lon(t:int):Number {
 110                         return (t/Math.pow(2,map.scale)*360-180);
 111                 }
 112                 private function tile2lat(t:int):Number {
 113                         var n:Number=Math.PI-2*Math.PI*t/Math.pow(2,map.scale);
 114                         return (180/Math.PI*Math.atan(0.5*(Math.exp(n)-Math.exp(-n))));
 115                 }
 116
 117         }
 118 }