root/lang/actionscript/metro-map/GMapCalc.as @ 14637

package
{
        import flash.geom.Point;

        public class GMapCalc
        {
                public static const DEFAULT_TILE_SIZE:int = 256;
                public static var   TILE_SIZE:int         = DEFAULT_TILE_SIZE;
                
                private static function bround(v:Number, min:Number, max:Number):Number
                {
                        if (v>max) return max;
                        if (v<min) return min;
                        return v;
                }
                
                public static function XYtoLatLng(x:Number, y:Number, out:LatLng):Boolean
                {
                        const PI:Number = Math.PI;
                        const DPI:Number = PI * 2.0;
                        const HPI:Number = PI / 2.0;

                        var lng:Number = bround((x-0.5) * DPI, -PI, PI);
                        
                        var g:Number = (y-0.5) * -DPI;
                        var lat:Number = 2.0 * Math.atan( Math.exp(g) ) - HPI;
                        
                        out.lat = lat;
                        out.lng = lng;
                        return true;
                }
                
                public static function LatLngToXY(lat:Number, lng:Number, out:Point):Boolean
                {
                        const DPI:Number = Math.PI * 2.0;
                        const HPI:Number = Math.PI / 2.0;

                        var x:Number = lng/DPI + 0.5;

                        var s:Number = Math.sin(lat);
                        var c:Number = Math.cos(lat);
                        var y:Number = Math.log((1+c+s)/(1+c-s)) / -DPI + 0.5;
                        
                        out.x = x;
                        out.y = y;
                        
                        return true;
                }
                
                public static function calcMapSize(zoom:int):int
                {
                        return Math.pow(2, zoom+8);             
                }

                public static function calcMapTileCols(zoom:int):int
                {
                        return Math.pow(2, zoom);               
                }
                
                public static function calcTileData(x:Number, y:Number, zoom:int, layer:int):Object
                {
                        if (zoom < 0)
                                throw "illegal zoom level";

                        var mapSize:Number = calcMapSize(zoom);
                        var ox:int = Math.floor(x*mapSize) % TILE_SIZE;
                        var oy:int = Math.floor(y*mapSize) % TILE_SIZE;
                        var tx:int = Math.floor(x*mapSize / TILE_SIZE);
                        var ty:int = Math.floor(y*mapSize / TILE_SIZE);

                        switch(layer)
                        {
                        case 0:
                                return {tile_index: {x:tx, y:ty}, offset: {x:ox, y:oy}, tile_zoom: (17-zoom)};
                        }
        
                        throw "illegal layer index";
                }
                
                public static function calcTilePath(tx:int, ty:int, zoom:int):String
                {
                        var path:Array  = [];
                        var qrts:String = "qrts";

                        for (var i:int = 0;i < zoom;i++)
                        {
                                var t:int = (tx & 1) | ((ty & 1) << 1);
                                tx /= 2;
                                ty /= 2;
                                path.unshift( qrts.charAt(t) );
                        }
                        path.unshift( 't' );

                        return path.join('');
                }
                
                public static function calcMapsZoomIndex(z:int):int
                {
                        return 17-z;
                }
        }
}