缩放级别和磁贴网格

using System;
using System.Text;

namespace AzureMaps
{
    /// <summary>
    /// Tile System math for the Spherical Mercator projection coordinate system (EPSG:3857)
    /// </summary>
    public static class TileMath
    {
        //Earth radius in meters.
        private const double EarthRadius = 6378137;

        private const double MinLatitude = -85.05112878;
        private const double MaxLatitude = 85.05112878;
        private const double MinLongitude = -180;
        private const double MaxLongitude = 180;

        /// <summary>
        /// Clips a number to the specified minimum and maximum values.
        /// </summary>
        /// <param name="n">The number to clip.</param>
        /// <param name="minValue">Minimum allowable value.</param>
        /// <param name="maxValue">Maximum allowable value.</param>
        /// <returns>The clipped value.</returns>
        private static double Clip(double n, double minValue, double maxValue)
        {
            return Math.Min(Math.Max(n, minValue), maxValue);
        }

        /// <summary>
        /// Calculates width and height of the map in pixels at a specific zoom level from -180 degrees to 180 degrees.
        /// </summary>
        /// <param name="zoom">Zoom Level to calculate width at</param>
        /// <param name="tileSize">The size of the tiles in the tile pyramid.</param>
        /// <returns>Width and height of the map in pixels</returns>
        public static double MapSize(double zoom, int tileSize)
        {
            return Math.Ceiling(tileSize * Math.Pow(2, zoom));
        }

        /// <summary>
        /// Calculates the Ground resolution at a specific degree of latitude in meters per pixel.
        /// </summary>
        /// <param name="latitude">Degree of latitude to calculate resolution at</param>
        /// <param name="zoom">Zoom level to calculate resolution at</param>
        /// <param name="tileSize">The size of the tiles in the tile pyramid.</param>
        /// <returns>Ground resolution in meters per pixels</returns>
        public static double GroundResolution(double latitude, double zoom, int tileSize)
        {
            latitude = Clip(latitude, MinLatitude, MaxLatitude);
            return Math.Cos(latitude * Math.PI / 180) * 2 * Math.PI * EarthRadius / MapSize(zoom, tileSize);
        }

        /// <summary>
        /// Determines the map scale at a specified latitude, level of detail, and screen resolution.
        /// </summary>
        /// <param name="latitude">Latitude (in degrees) at which to measure the map scale.</param>
        /// <param name="zoom">Level of detail, from 1 (lowest detail) to 23 (highest detail).</param>
        /// <param name="screenDpi">Resolution of the screen, in dots per inch.</param>
        /// <param name="tileSize">The size of the tiles in the tile pyramid.</param>
        /// <returns>The map scale, expressed as the denominator N of the ratio 1 : N.</returns>
        public static double MapScale(double latitude, double zoom, int screenDpi, int tileSize)
        {
            return GroundResolution(latitude, zoom, tileSize) * screenDpi / 0.0254;
        }

        /// <summary>
        /// Global Converts a Pixel coordinate into a geospatial coordinate at a specified zoom level. 
        /// Global Pixel coordinates are relative to the top left corner of the map (90, -180)
        /// </summary>
        /// <param name="pixel">Pixel coordinates in the format of [x, y].</param>  
        /// <param name="zoom">Zoom level</param>
        /// <param name="tileSize">The size of the tiles in the tile pyramid.</param>
        /// <returns>A position value in the format [longitude, latitude].</returns>
        public static double[] GlobalPixelToPosition(double[] pixel, double zoom, int tileSize)
        {
            var mapSize = MapSize(zoom, tileSize);

            var x = (Clip(pixel[0], 0, mapSize - 1) / mapSize) - 0.5;
            var y = 0.5 - (Clip(pixel[1], 0, mapSize - 1) / mapSize);

            return new double[] {
                360 * x,    //Longitude
                90 - 360 * Math.Atan(Math.Exp(-y * 2 * Math.PI)) / Math.PI  //Latitude
            };
        }

        /// <summary>
        /// Converts a point from latitude/longitude WGS-84 coordinates (in degrees) into pixel XY coordinates at a specified level of detail.
        /// </summary>
        /// <param name="position">Position coordinate in the format [longitude, latitude]</param>
        /// <param name="zoom">Zoom level.</param>
        /// <param name="tileSize">The size of the tiles in the tile pyramid.</param> 
        /// <returns>A global pixel coordinate.</returns>
        public static double[] PositionToGlobalPixel(double[] position, int zoom, int tileSize)
        {
            var latitude = Clip(position[1], MinLatitude, MaxLatitude);
            var longitude = Clip(position[0], MinLongitude, MaxLongitude);

            var x = (longitude + 180) / 360;
            var sinLatitude = Math.Sin(latitude * Math.PI / 180);
            var y = 0.5 - Math.Log((1 + sinLatitude) / (1 - sinLatitude)) / (4 * Math.PI);

            var mapSize = MapSize(zoom, tileSize);

            return new double[] {
                 Clip(x * mapSize + 0.5, 0, mapSize - 1),
                 Clip(y * mapSize + 0.5, 0, mapSize - 1)
            };
        }

        /// <summary>
        /// Converts pixel XY coordinates into tile XY coordinates of the tile containing the specified pixel.
        /// </summary>
        /// <param name="pixel">Pixel coordinates in the format of [x, y].</param>  
        /// <param name="tileSize">The size of the tiles in the tile pyramid.</param>
        /// <param name="tileX">Output parameter receiving the tile X coordinate.</param>
        /// <param name="tileY">Output parameter receiving the tile Y coordinate.</param>
        public static void GlobalPixelToTileXY(double[] pixel, int tileSize, out int tileX, out int tileY)
        {
            tileX = (int)(pixel[0] / tileSize);
            tileY = (int)(pixel[1] / tileSize);
        }

        /// <summary>
        /// Performs a scale transform on a global pixel value from one zoom level to another.
        /// </summary>
        /// <param name="pixel">Pixel coordinates in the format of [x, y].</param>  
        /// <param name="oldZoom">The zoom level in which the input global pixel value is from.</param>  
        /// <returns>A scale pixel coordinate.</returns>
        public static double[] ScaleGlobalPixel(double[] pixel, double oldZoom, double newZoom)
        {
            var scale = Math.Pow(2, oldZoom - newZoom);

            return new double[] { pixel[0] * scale, pixel[1] * scale };
        }

        /// <summary>
        /// Performs a scale transform on a set of global pixel values from one zoom level to another.
        /// </summary>
        /// <param name="pixels">A set of global pixel value from the old zoom level. Points are in the format [x,y].</param>
        /// <param name="oldZoom">The zoom level in which the input global pixel values is from.</param>
        /// <param name="newZoom">The new zoom level in which the output global pixel values should be aligned with.</param>
        /// <returns>A set of global pixel values that has been scaled for the new zoom level.</returns>
        public static double[][] ScaleGlobalPixels(double[][] pixels, double oldZoom, double newZoom)
        {
            var scale = Math.Pow(2, oldZoom - newZoom);

            var output = new System.Collections.Generic.List<double[]>();
            foreach (var p in pixels)
            {
                output.Add(new double[] { p[0] * scale, p[1] * scale });
            }

            return output.ToArray();
        }

        /// <summary>
        /// Converts tile XY coordinates into a global pixel XY coordinates of the upper-left pixel of the specified tile.
        /// </summary>
        /// <param name="tileX">Tile X coordinate.</param>
        /// <param name="tileY">Tile Y coordinate.</param>
        /// <param name="tileSize">The size of the tiles in the tile pyramid.</param>
        /// <param name="pixelX">Output parameter receiving the X coordinate of the point, in pixels.</param>  
        /// <param name="pixelY">Output parameter receiving the Y coordinate of the point, in pixels.</param>  
        public static double[] TileXYToGlobalPixel(int tileX, int tileY, int tileSize)
        {
            return new double[] { tileX * tileSize, tileY * tileSize };
        }

        /// <summary>
        /// Converts tile XY coordinates into a quadkey at a specified level of detail.
        /// </summary>
        /// <param name="tileX">Tile X coordinate.</param>
        /// <param name="tileY">Tile Y coordinate.</param>
        /// <param name="zoom">Zoom level</param>
        /// <returns>A string containing the quadkey.</returns>
        public static string TileXYToQuadKey(int tileX, int tileY, int zoom)
        {
            var quadKey = new StringBuilder();
            for (int i = zoom; i > 0; i--)
            {
                char digit = '0';
                int mask = 1 << (i - 1);
                if ((tileX & mask) != 0)
                {
                    digit++;
                }
                if ((tileY & mask) != 0)
                {
                    digit++;
                    digit++;
                }
                quadKey.Append(digit);
            }
            return quadKey.ToString();
        }

        /// <summary>
        /// Converts a quadkey into tile XY coordinates.
        /// </summary>
        /// <param name="quadKey">Quadkey of the tile.</param>
        /// <param name="tileX">Output parameter receiving the tile X coordinate.</param>
        /// <param name="tileY">Output parameter receiving the tile Y coordinate.</param>
        /// <param name="zoom">Output parameter receiving the zoom level.</param>
        public static void QuadKeyToTileXY(string quadKey, out int tileX, out int tileY, out int zoom)
        {
            tileX = tileY = 0;
            zoom = quadKey.Length;
            for (int i = zoom; i > 0; i--)
            {
                int mask = 1 << (i - 1);
                switch (quadKey[zoom - i])
                {
                    case '0':
                        break;

                    case '1':
                        tileX |= mask;
                        break;

                    case '2':
                        tileY |= mask;
                        break;

                    case '3':
                        tileX |= mask;
                        tileY |= mask;
                        break;

                    default:
                        throw new ArgumentException("Invalid QuadKey digit sequence.");
                }
            }
        }

        /// <summary>
        /// Calculates the XY tile coordinates that a coordinate falls into for a specific zoom level.
        /// </summary>
        /// <param name="position">Position coordinate in the format [longitude, latitude]</param>
        /// <param name="zoom">Zoom level</param>
        /// <param name="tileSize">The size of the tiles in the tile pyramid.</param>
        /// <param name="tileX">Output parameter receiving the tile X position.</param>
        /// <param name="tileY">Output parameter receiving the tile Y position.</param>
        public static void PositionToTileXY(double[] position, int zoom, int tileSize, out int tileX, out int tileY)
        {
            var latitude = Clip(position[1], MinLatitude, MaxLatitude);
            var longitude = Clip(position[0], MinLongitude, MaxLongitude);

            var x = (longitude + 180) / 360;
            var sinLatitude = Math.Sin(latitude * Math.PI / 180);
            var y = 0.5 - Math.Log((1 + sinLatitude) / (1 - sinLatitude)) / (4 * Math.PI);

            //tileSize needed in calculations as in rare cases the multiplying/rounding/dividing can make the difference of a pixel which can result in a completely different tile. 
            var mapSize = MapSize(zoom, tileSize);
            tileX = (int)Math.Floor(Clip(x * mapSize + 0.5, 0, mapSize - 1) / tileSize);
            tileY = (int)Math.Floor(Clip(y * mapSize + 0.5, 0, mapSize - 1) / tileSize);
        }

        /// <summary>
        /// Calculates the tile quadkey strings that are within a specified viewport.
        /// </summary>
        /// <param name="position">Position coordinate in the format [longitude, latitude]</param>
        /// <param name="zoom">Zoom level</param>
        /// <param name="width">The width of the map viewport in pixels.</param>
        /// <param name="height">The height of the map viewport in pixels.</param>
        /// <param name="tileSize">The size of the tiles in the tile pyramid.</param>
        /// <returns>A list of quadkey strings that are within the specified viewport.</returns>
        public static string[] GetQuadkeysInView(double[] position, int zoom, int width, int height, int tileSize)
        {
            var p = PositionToGlobalPixel(position, zoom, tileSize);

            var top = p[1] - height * 0.5;
            var left = p[0] - width * 0.5;

            var bottom = p[1] + height * 0.5;
            var right = p[0] + width * 0.5;

            var tl = GlobalPixelToPosition(new double[] { left, top }, zoom, tileSize);
            var br = GlobalPixelToPosition(new double[] { right, bottom }, zoom, tileSize);

            //Boudning box in the format: [west, south, east, north];
            var bounds = new double[] { tl[0], br[1], br[0], tl[1] };

            return GetQuadkeysInBoundingBox(bounds, zoom, tileSize);
        }

        /// <summary>
        /// Calculates the tile quadkey strings that are within a bounding box at a specific zoom level.
        /// </summary>
        /// <param name="bounds">A bounding box defined as an array of numbers in the format of [west, south, east, north].</param>
        /// <param name="zoom">Zoom level to calculate tiles for.</param>
        /// <param name="tileSize">The size of the tiles in the tile pyramid.</param>
        /// <returns>A list of quadkey strings.</returns>
        public static string[] GetQuadkeysInBoundingBox(double[] bounds, int zoom, int tileSize)
        {
            var keys = new System.Collections.Generic.List<string>();

            if (bounds != null && bounds.Length >= 4)
            {
                PositionToTileXY(new double[] { bounds[3], bounds[0] }, zoom, tileSize, out int tlX, out int tlY);
                PositionToTileXY(new double[] { bounds[1], bounds[2] }, zoom, tileSize, out int brX, out int brY);

                for (int x = tlX; x <= brX; x++)
                {
                    for (int y = tlY; y <= brY; y++)
                    {
                        keys.Add(TileXYToQuadKey(x, y, zoom));
                    }
                }
            }

            return keys.ToArray();
        }

        /// <summary>
        /// Calculates the bounding box of a tile.
        /// </summary>
        /// <param name="tileX">Tile X coordinate</param>
        /// <param name="tileY">Tile Y coordinate</param>
        /// <param name="zoom">Zoom level</param>
        /// <param name="tileSize">The size of the tiles in the tile pyramid.</param>
        /// <returns>A bounding box of the tile defined as an array of numbers in the format of [west, south, east, north].</returns>
        public static double[] TileXYToBoundingBox(int tileX, int tileY, double zoom, int tileSize)
        {
            //Top left corner pixel coordinates
            var x1 = (double)(tileX * tileSize);
            var y1 = (double)(tileY * tileSize);

            //Bottom right corner pixel coordinates
            var x2 = (double)(x1 + tileSize);
            var y2 = (double)(y1 + tileSize);

            var nw = GlobalPixelToPosition(new double[] { x1, y1 }, zoom, tileSize);
            var se = GlobalPixelToPosition(new double[] { x2, y2 }, zoom, tileSize);

            return new double[] { nw[0], se[1], se[0], nw[1] };
        }

        /// <summary>
        /// Calculates the best map view (center, zoom) for a bounding box on a map.
        /// </summary>
        /// <param name="bounds">A bounding box defined as an array of numbers in the format of [west, south, east, north].</param>
        /// <param name="mapWidth">Map width in pixels.</param>
        /// <param name="mapHeight">Map height in pixels.</param>
        /// <param name="latitude">Output parameter receiving the center latitude coordinate.</param>
        /// <param name="longitude">Output parameter receiving the center longitude coordinate.</param>
        /// <param name="zoom">Output parameter receiving the zoom level</param>
        /// <param name="padding">Width in pixels to use to create a buffer around the map. This is to keep markers from being cut off on the edge. Default: 0</param>
        /// <param name="tileSize">The size of the tiles in the tile pyramid. Default: 512</param>
        /// <param name="maxZoom">Optional maximum zoom level to return. Useful when the bounding box represents a very small area. Default: 24</param>
        /// <param name="allowFloatZoom">Specifies if the returned zoom level should be a float or rounded down to an whole integer zoom level. Default: true</param>
        public static void BestMapView(BoundingBox bounds, double mapWidth, double mapHeight, out double centerLat, out double centerLon, out double zoom, int padding = 0, int tileSize = 512, double maxZoom = 24, bool allowFloatZoom = true)
        {
        	centerLat = 0;
        	centerLon = 0;
        	zoom = 0;
        
        	if (bounds != null && mapWidth > 0 && mapHeight > 0)
        	{
        		//Ensure padding is valid.
        		padding = Math.Abs(padding);
        
        		//Ensure max zoom is within valid range.
        		maxZoom = Clip(maxZoom, 0, 24);
        
        		//Do pixel calculations at zoom level 24 as that will provide a high level of visual accuracy.
        		int pixelZoom = 24;
        
        		//Calculate mercator pixel coordinate at zoom level 24.
        		var wnPixel = PositionToGlobalPixel(new double[] { bounds[0], bounds[3] }, pixelZoom, tileSize);
        		var esPixel = PositionToGlobalPixel(new double[] { bounds[2], bounds[1] }, pixelZoom, tileSize);
        
        		//Calculate the pixel distance between pixels for each axis.
        		double dx = esPixel[0] - wnPixel[0];
        		double dy = esPixel[1] - wnPixel[1];
        
        		//Calculate the average pixel positions to get the visual center.
        		double xAvg = (esPixel[0] + wnPixel[0]) / 2;
        		double yAvg = (esPixel[1] + wnPixel[1]) / 2;
        
        		//Determine if the bounding box crosses the antimeridian. (West pixel will be greater than East pixel).
        		if (wnPixel[0] > esPixel[0])
        		{
        			double mapSize = MapSize(24, tileSize);
        
        			//We are interested in the opposite area of the map. Calculate the opposite area and visual center.
        			dx = mapSize - Math.Abs(dx);
        
        			//Offset the visual center by half the global map width at zoom 24 on the x axis.
        			xAvg += mapSize / 2;
        		}
        
        		//Convert visual center pixel from zoom 24 to lngLat.
        		center = GlobalPixelToPosition(new Pixel(xAvg, yAvg), pixelZoom, tileSize);
        
        		//Calculate scale of screen pixels per unit on the Web Mercator plane.
        		double scaleX = (mapWidth - padding * 2) / Math.Abs(dx) * Math.Pow(2, pixelZoom);
        		double scaleY = (mapHeight - padding * 2) / Math.Abs(dy) * Math.Pow(2, pixelZoom);
        
        		//Calculate zoom levels based on the x/y scales. Choose the most zoomed out value.
        		zoom = Math.Max(0, Math.Min(maxZoom, Math.Log2(Math.Abs(Math.Min(scaleX, scaleY)))));
        
        		//Round down zoom level if float values are not desired.
        		if (!allowFloatZoom)
        		{
        			zoom = Math.Floor(zoom);
        		}
        	}
        
        	return new CameraOptions
        	{
        		Center = center,
        		Zoom = zoom
        	};
        }
    }
}

module AzureMaps {

    /** Tile System math for the Spherical Mercator projection coordinate system (EPSG:3857) */
    export class TileMath {
        //Earth radius in meters.
        private static EarthRadius = 6378137;

        private static MinLatitude = -85.05112878;
        private static MaxLatitude = 85.05112878;
        private static MinLongitude = -180;
        private static MaxLongitude = 180;

        /**
         * Clips a number to the specified minimum and maximum values.
         * @param n The number to clip.
         * @param minValue Minimum allowable value.
         * @param maxValue Maximum allowable value.
         * @returns The clipped value.
         */
        private static Clip(n: number, minValue: number, maxValue: number): number {
            return Math.min(Math.max(n, minValue), maxValue);
        }

        /**
         * Calculates width and height of the map in pixels at a specific zoom level from -180 degrees to 180 degrees.
         * @param zoom Zoom Level to calculate width at.
         * @param tileSize The size of the tiles in the tile pyramid.
         * @returns Width and height of the map in pixels.
         */
        public static MapSize(zoom: number, tileSize: number): number {
            return Math.ceil(tileSize * Math.pow(2, zoom));
        }

        /**
         * Calculates the Ground resolution at a specific degree of latitude in the meters per pixel.
         * @param latitude Degree of latitude to calculate resolution at.
         * @param zoom Zoom level.
         * @param tileSize The size of the tiles in the tile pyramid.
         * @returns Ground resolution in meters per pixels.
         */
        public static GroundResolution(latitude: number, zoom: number, tileSize: number): number {
            latitude = this.Clip(latitude, this.MinLatitude, this.MaxLatitude);
            return Math.cos(latitude * Math.PI / 180) * 2 * Math.PI * this.EarthRadius / this.MapSize(zoom, tileSize);
        }

        /**
         * Determines the map scale at a specified latitude, level of detail, and screen resolution.
         * @param latitude Latitude (in degrees) at which to measure the map scale.
         * @param zoom Zoom level.
         * @param screenDpi Resolution of the screen, in dots per inch.
         * @param tileSize The size of the tiles in the tile pyramid.
         * @returns The map scale, expressed as the denominator N of the ratio 1 : N.
         */
        public static MapScale(latitude: number, zoom: number, screenDpi: number, tileSize: number): number {
            return this.GroundResolution(latitude, zoom, tileSize) * screenDpi / 0.0254;
        }

        /**
         * Global Converts a Pixel coordinate into a geospatial coordinate at a specified zoom level.
         * Global Pixel coordinates are relative to the top left corner of the map (90, -180).
         * @param pixel Pixel coordinates in the format of [x, y].
         * @param zoom Zoom level.
         * @param tileSize The size of the tiles in the tile pyramid.
         * @returns A position value in the format [longitude, latitude].
         */
        public static GlobalPixelToPosition(pixel: number[], zoom: number, tileSize: number): number[] {
            var mapSize = this.MapSize(zoom, tileSize);

            var x = (this.Clip(pixel[0], 0, mapSize - 1) / mapSize) - 0.5;
            var y = 0.5 - (this.Clip(pixel[1], 0, mapSize - 1) / mapSize);

            return [
                360 * x,    //Longitude
                90 - 360 * Math.atan(Math.exp(-y * 2 * Math.PI)) / Math.PI  //Latitude
            ];
        }

        /**
         * Converts a point from latitude/longitude WGS-84 coordinates (in degrees) into pixel XY coordinates at a specified level of detail.
         * @param position Position coordinate in the format [longitude, latitude].
         * @param zoom Zoom level.
         * @param tileSize The size of the tiles in the tile pyramid.
         * @returns A pixel coordinate 
         */
        public static PositionToGlobalPixel(position: number[], zoom: number, tileSize: number): number[] {
            var latitude = this.Clip(position[1], this.MinLatitude, this.MaxLatitude);
            var longitude = this.Clip(position[0], this.MinLongitude, this.MaxLongitude);

            var x = (longitude + 180) / 360;
            var sinLatitude = Math.sin(latitude * Math.PI / 180);
            var y = 0.5 - Math.log((1 + sinLatitude) / (1 - sinLatitude)) / (4 * Math.PI);

            var mapSize = this.MapSize(zoom, tileSize);

            return [
                this.Clip(x * mapSize + 0.5, 0, mapSize - 1),
                this.Clip(y * mapSize + 0.5, 0, mapSize - 1)
            ];
        }

        /**
         * Converts pixel XY coordinates into tile XY coordinates of the tile containing the specified pixel.
         * @param pixel Pixel coordinates in the format of [x, y].
         * @param tileSize The size of the tiles in the tile pyramid.
         * @returns Tile XY coordinates.
         */
        public static GlobalPixelToTileXY(pixel: number[], tileSize: number): { tileX: number, tileY: number } {
            return {
                tileX: Math.round(pixel[0] / tileSize),
                tileY: Math.round(pixel[1] / tileSize)
            };
        }

        /**
         * Performs a scale transform on a global pixel value from one zoom level to another.
         * @param pixel Pixel coordinates in the format of [x, y].
         * @param oldZoom The zoom level in which the input global pixel value is from.
         * @param newZoom The new zoom level in which the output global pixel value should be aligned with.
         */
        public static ScaleGlobalPixel(pixel: number[], oldZoom: number, newZoom: number): number[] {
            var scale = Math.pow(2, oldZoom - newZoom);

            return [pixel[0] * scale, pixel[1] * scale];
        }

        /// <summary>
        /// Performs a scale transform on a set of global pixel values from one zoom level to another.
        /// </summary>
        /// <param name="points">A set of global pixel value from the old zoom level. Points are in the format [x,y].</param>
        /// <param name="oldZoom">The zoom level in which the input global pixel values is from.</param>
        /// <param name="newZoom">The new zoom level in which the output global pixel values should be aligned with.</param>
        /// <returns>A set of global pixel values that has been scaled for the new zoom level.</returns>
        public static ScaleGlobalPixels(pixels: number[][], oldZoom: number, newZoom: number): number[][] {
            var scale = Math.pow(2, oldZoom - newZoom);

            var output: number[][] = [];
            for (var i = 0, len = pixels.length; i < len; i++) {
                output.push([pixels[i][0] * scale, pixels[i][1] * scale]);
            }

            return output;
        }

        /**
         * Converts tile XY coordinates into a global pixel XY coordinates of the upper-left pixel of the specified tile.
         * @param tileX Tile X coordinate.
         * @param tileY Tile Y coordinate.
         * @param tileSize The size of the tiles in the tile pyramid.
         * @returns Pixel coordinates in the format of [x, y].
         */
        public static TileXYToGlobalPixel(tileX, tileY, tileSize): number[] {
            return [tileX * tileSize, tileY * tileSize];
        }

        /**
         * Converts tile XY coordinates into a quadkey at a specified level of detail.
         * @param tileX Tile X coordinate.
         * @param tileY Tile Y coordinate.
         * @param zoom Zoom level.
         * @returns A string containing the quadkey.
         */
        public static TileXYToQuadKey(tileX: number, tileY: number, zoom: number): string {
            var quadKey: number[] = [];
            for (var i = zoom; i > 0; i--) {
                var digit = 0;
                var mask = 1 << (i - 1);

                if ((tileX & mask) != 0) {
                    digit++;
                }

                if ((tileY & mask) != 0) {
                    digit += 2
                }

                quadKey.push(digit);
            }
            return quadKey.join('');
        }

        /**
         * Converts a quadkey into tile XY coordinates.
         * @param quadKey Quadkey of the tile.
         * @returns Tile XY coordinates and zoom level for the specified quadkey.
         */
        public static QuadKeyToTileXY(quadKey: string): { tileX: number, tileY: number, zoom: number } {
            var tileX = 0;
            var tileY = 0;
            var zoom = quadKey.length;

            for (var i = zoom; i > 0; i--) {
                var mask = 1 << (i - 1);
                switch (quadKey[zoom - i]) {
                    case '0':
                        break;

                    case '1':
                        tileX |= mask;
                        break;

                    case '2':
                        tileY |= mask;
                        break;

                    case '3':
                        tileX |= mask;
                        tileY |= mask;
                        break;

                    default:
                        throw "Invalid QuadKey digit sequence.";
                }
            }

            return {
                tileX: tileX,
                tileY: tileY,
                zoom: zoom
            };
        }

        /**
         * Calculates the XY tile coordinates that a coordinate falls into for a specific zoom level.
         * @param position Position coordinate in the format [longitude, latitude].
         * @param zoom Zoom level.
         * @param tileSize The size of the tiles in the tile pyramid.
         * @returns Tile XY coordinates.
         */
        public static PositionToTileXY(position: number[], zoom: number, tileSize: number): { tileX: number, tileY: number } {
            var latitude = this.Clip(position[1], this.MinLatitude, this.MaxLatitude);
            var longitude = this.Clip(position[0], this.MinLongitude, this.MaxLongitude);

            var x = (longitude + 180) / 360;
            var sinLatitude = Math.sin(latitude * Math.PI / 180);
            var y = 0.5 - Math.log((1 + sinLatitude) / (1 - sinLatitude)) / (4 * Math.PI);

            //tileSize needed in calculations as in rare cases the multiplying/rounding/dividing can make the difference of a pixel which can result in a completely different tile. 
            var mapSize = this.MapSize(zoom, tileSize);

            return {
                tileX: Math.floor(this.Clip(x * mapSize + 0.5, 0, mapSize - 1) / tileSize),
                tileY: Math.floor(this.Clip(y * mapSize + 0.5, 0, mapSize - 1) / tileSize)
            };
        }

        /**
         * Calculates the tile quadkey strings that are within a specified viewport.
         * @param position Position coordinate in the format [longitude, latitude].
         * @param zoom Zoom level.
         * @param width The width of the map viewport in pixels.
         * @param height The height of the map viewport in pixels.
         * @param tileSize The size of the tiles in the tile pyramid.
         * @returns A list of quadkey strings that are within the specified viewport.
         */
        public static GetQuadkeysInView(position: number[], zoom: number, width: number, height: number, tileSize: number): string[] {
            var p = this.PositionToGlobalPixel(position, zoom, tileSize);

            var top = p[1] - height * 0.5;
            var left = p[0] - width * 0.5;

            var bottom = p[1] + height * 0.5;
            var right = p[0] + width * 0.5;

            var tl = this.GlobalPixelToPosition([left, top], zoom, tileSize);
            var br = this.GlobalPixelToPosition([right, bottom], zoom, tileSize);

            //Boudning box in the format: [west, south, east, north];
            var bounds = [tl[0], br[1], br[0], tl[1]];

            return this.GetQuadkeysInBoundingBox(bounds, zoom, tileSize);
        }

        /**
         * Calculates the tile quadkey strings that are within a bounding box at a specific zoom level.
         * @param bounds A bounding box defined as an array of numbers in the format of [west, south, east, north].
         * @param zoom Zoom level to calculate tiles for.
         * @param tileSize The size of the tiles in the tile pyramid.
         * @returns A list of quadkey strings.
         */
        public static GetQuadkeysInBoundingBox(bounds: number[], zoom: number, tileSize: number): string[] {
            var keys: string[] = [];

            if (bounds != null && bounds.length >= 4) {
                var tl = this.PositionToTileXY([bounds[0], bounds[3]], zoom, tileSize);
                var br = this.PositionToTileXY([bounds[2], bounds[1]], zoom, tileSize);

                for (var x = tl[0]; x <= br[0]; x++) {
                    for (var y = tl[1]; y <= br[1]; y++) {
                        keys.push(this.TileXYToQuadKey(x, y, zoom));
                    }
                }
            }

            return keys;
        }

        /**
         * Calculates the bounding box of a tile.
         * @param tileX Tile X coordinate.
         * @param tileY Tile Y coordinate.
         * @param zoom Zoom level.
         * @param tileSize The size of the tiles in the tile pyramid.
         * @returns A bounding box of the tile defined as an array of numbers in the format of [west, south, east, north].
         */
        public static TileXYToBoundingBox(tileX: number, tileY: number, zoom: number, tileSize: number): number[] {
            //Top left corner pixel coordinates
            var x1 = tileX * tileSize;
            var y1 = tileY * tileSize;

            //Bottom right corner pixel coordinates
            var x2 = x1 + tileSize;
            var y2 = y1 + tileSize;

            var nw = this.GlobalPixelToPosition([x1, y1], zoom, tileSize);
            var se = this.GlobalPixelToPosition([x2, y2], zoom, tileSize);

            return [nw[0], se[1], se[0], nw[1]];
        }

        /**
         * Calculates the best map view (center, zoom) for a bounding box on a map.
         * @param bounds A bounding box defined as an array of numbers in the format of [west, south, east, north]. 
         * @param mapWidth Map width in pixels.
         * @param mapHeight Map height in pixels.
         * @param padding Width in pixels to use to create a buffer around the map. This is to keep markers from being cut off on the edge.
         * @param tileSize The size of the tiles in the tile pyramid.
         * @param maxZoom Optional maximum zoom level to return. Useful when the bounding box represents a very small area.
         * @param allowFloatZoom Specifies if the returned zoom level should be a float or rounded down to an whole integer zoom level. 
         * @returns The center and zoom level to best position the map view over the provided bounding box.
         */
        public static BestMapView(bounds: number, mapWidth: number, mapHeight: number, padding: number = 0, tileSize: number = 512, maxZoom: number = 24, allowFloatZoom: boolean = true): { center: number[], zoom: number } {
        	//Ensure valid bounds and map dimensions are provided.
        	if (bounds == null || bounds.length < 4 || !mapWidth || !mapHeight || mapWidth <= 0 || mapHeight <= 0) {
        		return {
        			center: [0, 0],
        			zoom: 0
        		};
        	}
        
        	//Ensure padding is valid.
        	padding = Math.abs(padding || 0);
        	
        	//Ensure max zoom is within valid range.
        	maxZoom = this.Clip(maxZoom, 0, 24);
        	
        	//Do pixel calculations at zoom level 24 as that will provide a high level of visual accuracy.
        	const pixelZoom = 24;
        
        	//Calculate mercator pixel coordinate at zoom level 24.
        	const wnPixel = this.PositionToGlobalPixel([bounds[0], bounds[3]], pixelZoom, tileSize);
        	const esPixel = this.PositionToGlobalPixel([bounds[2], bounds[1]], pixelZoom, tileSize);
        	
        	//Calculate the pixel distance between pixels for each axis.
        	let dx = esPixel[0] - wnPixel[0];
        	const dy = esPixel[1] - wnPixel[1];
        	
        	//Calculate the average pixel positions to get the visual center.
        	let xAvg = (esPixel[0] + wnPixel[0]) / 2;
        	const yAvg = (esPixel[1] + wnPixel[1]) / 2;
        		
        	//Determine if the bounding box crosses the antimeridian. (West pixel will be greater than East pixel).
        	if(wnPixel[0] > esPixel[0]) {
        		const mapSize = this.MapSize(24, tileSize);
		
        		//We are interested in the opposite area of the map. Calculate the opposite area and visual center.
        		dx = mapSize - Math.abs(dx);
        		
        		//Offset the visual center by half the global map width at zoom 24 on the x axis.
        		xAvg += mapSize / 2;		
        	}
        
        	//Convert visual center pixel from zoom 24 to lngLat.
        	const centerLngLat = this.GlobalPixelToPosition([xAvg, yAvg], pixelZoom, tileSize);
        
        	//Calculate scale of screen pixels per unit on the Web Mercator plane.
        	const scaleX = (mapWidth - padding * 2) / Math.abs(dx) * Math.pow(2, pixelZoom);
        	const scaleY = (mapHeight - padding * 2) / Math.abs(dy) * Math.pow(2, pixelZoom);
        
        	//Calculate zoom levels based on the x/y scales. Choose the most zoomed out value.
        	let zoom = Math.max(0, Math.min(maxZoom, Math.log2(Math.abs(Math.min(scaleX, scaleY)))));
        
        	//Round down zoom level if float values are not desired.
        	if(!allowFloatZoom) {
        		zoom = Math.floor(zoom);
        	}
        
        	return {
        		center: centerLngLat,
        		zoom
        	};
        }
    }
}