XAML-Map-Control/MapControl/Shared/WmsImageLayer.cs

// XAML Map Control - https://github.com/ClemensFischer/XAML-Map-Control
// © 2019 Clemens Fischer
// Licensed under the Microsoft Public License (Ms-PL)

using System;
using System.Collections.Generic;
using System.Diagnostics;
using System.Linq;
using System.Threading.Tasks;
using System.Globalization;
#if WINDOWS_UWP
using Windows.Data.Xml.Dom;
using Windows.Foundation;
using Windows.UI.Xaml;
using Windows.UI.Xaml.Media;
#else
using System.Xml;
using System.Windows;
using System.Windows.Media;
#endif

namespace MapControl
{
    public partial class WmsImageLayer : MapImageLayer
    {
        public static readonly DependencyProperty ServiceUriProperty = DependencyProperty.Register(
            nameof(ServiceUri), typeof(Uri), typeof(WmsImageLayer),
            new PropertyMetadata(null, async (o, e) => await ((WmsImageLayer)o).UpdateImageAsync()));

        public static readonly DependencyProperty LayersProperty = DependencyProperty.Register(
            nameof(Layers), typeof(string), typeof(WmsImageLayer),
            new PropertyMetadata(string.Empty, async (o, e) => await ((WmsImageLayer)o).UpdateImageAsync()));

        public static readonly DependencyProperty StylesProperty = DependencyProperty.Register(
            nameof(Styles), typeof(string), typeof(WmsImageLayer),
            new PropertyMetadata(string.Empty, async (o, e) => await ((WmsImageLayer)o).UpdateImageAsync()));

        public static readonly DependencyProperty FormatProperty = DependencyProperty.Register(
            nameof(Format), typeof(string), typeof(WmsImageLayer),
            new PropertyMetadata("image/png", async (o, e) => await ((WmsImageLayer)o).UpdateImageAsync()));

        public static readonly DependencyProperty CrsIdMapProperty = DependencyProperty.Register(
            nameof(CrsIdMap), typeof(string), typeof(WmsImageLayer),
            new PropertyMetadata(null, async (o, e) => await ((WmsImageLayer)o).CrsIdMapPropertyChanged((string)e.NewValue)));

        public Uri ServiceUri
        {
            get { return (Uri)GetValue(ServiceUriProperty); }
            set { SetValue(ServiceUriProperty, value); }
        }

        public string Layers
        {
            get { return (string)GetValue(LayersProperty); }
            set { SetValue(LayersProperty, value); }
        }

        public string Styles
        {
            get { return (string)GetValue(StylesProperty); }
            set { SetValue(StylesProperty, value); }
        }

        public string Format
        {
            get { return (string)GetValue(FormatProperty); }
            set { SetValue(FormatProperty, value); }
        }

        public string CrsIdMap
        {
            get { return (string)GetValue(CrsIdMapProperty); }
            set { SetValue(CrsIdMapProperty, value); }
        }

        private Dictionary<string, string> crsIdMap;

        /// <summary>
        /// Gets a list of all layer names returned by a GetCapabilities response.
        /// </summary>
        public async Task<IList<string>> GetLayerNamesAsync()
        {
            IList<string> layerNames = null;

            if (ServiceUri != null)
            {
                var uri = GetRequestUri("GetCapabilities");

                try
                {
                    var document = await XmlDocument.LoadFromUriAsync(new Uri(uri.Replace(" ", "%20")));
                    layerNames = new List<string>();

                    var capability = ChildElements(document.DocumentElement, "Capability").FirstOrDefault();
                    if (capability != null)
                    {
                        var rootLayer = ChildElements(capability, "Layer").FirstOrDefault();
                        if (rootLayer != null)
                        {
                            foreach (var layer in ChildElements(rootLayer, "Layer"))
                            {
                                var name = ChildElements(layer, "Name").FirstOrDefault();
                                if (name != null)
                                {
                                    layerNames.Add(name.InnerText);
                                }
                            }
                        }
                    }
                }
                catch (Exception ex)
                {
                    Debug.WriteLine("WmsImageLayer: {0}: {1}", uri, ex.Message);
                }
            }

            return layerNames;
        }

        protected override async Task<ImageSource> GetImageAsync()
        {
            var uri = GetImageUri();

            return uri != null ? await ImageLoader.LoadImageAsync(uri) : null;
        }

        /// <summary>
        /// Returns a GetMap request URL for the current BoundingBox.
        /// </summary>
        protected virtual Uri GetImageUri()
        {
            Uri imageUri = null;
            var projection = ParentMap?.MapProjection;

            if (ServiceUri != null && projection != null && !string.IsNullOrEmpty(projection.CrsId))
            {
                var uri = GetRequestUri("GetMap");

                if (uri.IndexOf("LAYERS=", StringComparison.OrdinalIgnoreCase) < 0 && Layers != null)
                {
                    uri += "&LAYERS=" + Layers;
                }

                if (uri.IndexOf("STYLES=", StringComparison.OrdinalIgnoreCase) < 0 && Styles != null)
                {
                    uri += "&STYLES=" + Styles;
                }

                if (uri.IndexOf("FORMAT=", StringComparison.OrdinalIgnoreCase) < 0 && Format != null)
                {
                    uri += "&FORMAT=" + Format;
                }

                var crs = GetCrsValue();
                var rect = projection.BoundingBoxToRect(BoundingBox);

                uri += "&" + GetBboxParameters(crs, rect);
                uri += "&WIDTH=" + (int)Math.Round(projection.ViewportScale * rect.Width);
                uri += "&HEIGHT=" + (int)Math.Round(projection.ViewportScale * rect.Height);

                imageUri = new Uri(uri.Replace(" ", "%20"));
            }

            return imageUri;
        }

        /// <summary>
        /// Gets the effective value of the CRS query parameter.
        /// </summary>
        /// <returns></returns>
        protected virtual string GetCrsValue()
        {
            var projection = ParentMap.MapProjection;
            var crsId = projection.CrsId;

            if (crsIdMap != null && !crsIdMap.TryGetValue(crsId, out crsId))
            {
                crsId = projection.CrsId;
            }

            if (crsId.StartsWith("AUTO2:") || crsId.StartsWith("AUTO:"))
            {
                crsId = string.Format(CultureInfo.InvariantCulture, "{0},1,{1},{2}",
                    crsId, projection.ProjectionCenter.Longitude, projection.ProjectionCenter.Latitude);
            }

            return crsId;
        }

        /// <summary>
        /// Gets a query substring for the projected bounding box, which contains the CRS and BBOX or equivalent parameters.
        /// </summary>
        protected virtual string GetBboxParameters(string crs, Rect bbox)
        {
            return string.Format(CultureInfo.InvariantCulture,
                crs == "EPSG:4326" ? "CRS={0}&BBOX={2},{1},{4},{3}" : "CRS={0}&BBOX={1},{2},{3},{4}",
                crs, bbox.X, bbox.Y, (bbox.X + bbox.Width), (bbox.Y + bbox.Height));
        }

        private string GetRequestUri(string request)
        {
            var uri = ServiceUri.ToString();

            if (!uri.EndsWith("?") && !uri.EndsWith("&"))
            {
                uri += !uri.Contains("?") ? "?" : "&";
            }

            if (uri.IndexOf("SERVICE=", StringComparison.OrdinalIgnoreCase) < 0)
            {
                uri += "SERVICE=WMS&";
            }

            if (uri.IndexOf("VERSION=", StringComparison.OrdinalIgnoreCase) < 0)
            {
                uri += "VERSION=1.3.0&";
            }

            return uri + "REQUEST=" + request;
        }

        private Task CrsIdMapPropertyChanged(string crsIdMapString)
        {
            crsIdMap = null;

            if (!string.IsNullOrEmpty(crsIdMapString))
            {
                var entries = crsIdMapString.Split(new char[] { ' ', ',', ';' }, StringSplitOptions.RemoveEmptyEntries);

                if (entries.Length >= 2)
                {
                    crsIdMap = new Dictionary<string, string>();

                    for (int i = 0; i < entries.Length - 1; i += 2)
                    {
                        crsIdMap[entries[i]] = entries[i + 1];
                    }
                }
            }

            return UpdateImageAsync();
        }

        private static IEnumerable<XmlElement> ChildElements(XmlElement element, string name)
        {
            return element.ChildNodes.OfType<XmlElement>().Where(e => (string)e.LocalName == name);
        }
    }
}