Style WMS layers

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Change the style of a Web Map Service (WMS) layer.

Image of style WMS layers

Use case

Layers hosted on WMS may have different pre-set styles available to apply to them. Swapping between these styles can help during visual examination of the data. For example, increasing the contrast of satellite images can help in identifying urban and agricultural areas within forested areas.

How to use the sample

Once the layer loads, the toggle button will be enabled. Tap it to toggle between the first and second styles of the WMS layer.

How it works

  1. Create a WmsLayer specifying the URL of the service and the layer names you want new WmsLayer(url, names).
  2. When the layer is done loading, get it's list of style strings using wmsLayer.Sublayers[0].SublayerInfo.Styles.
  3. Set one of the styles using the wmsLayer.Sublayers[0].CurrentStyle property.

Relevant API

  • WmsLayer
  • WmsSublayer
  • WmsSublayerInfo

About the data

This sample uses a public service managed by the State of Minnesota and provides composite imagery for the state and the surrounding areas.

Tags

imagery, styles, visualization, WMS

Sample Code

StyleWmsLayer.cs
                                                                                                                                                             
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// Copyright 2018 Esri.
//
// Licensed under the Apache License, Version 2.0 (the "License"); you may not use this file except in compliance with the License.
// You may obtain a copy of the License at: http://www.apache.org/licenses/LICENSE-2.0
//
// Unless required by applicable law or agreed to in writing, software distributed under the License is distributed on an
// "AS IS" BASIS, WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied. See the License for the specific
// language governing permissions and limitations under the License.

using System;
using System.Collections.Generic;
using Esri.ArcGISRuntime.Geometry;
using Esri.ArcGISRuntime.Mapping;
using Esri.ArcGISRuntime.UI.Controls;
using Foundation;
using UIKit;

namespace ArcGISRuntime.Samples.StyleWmsLayer
{
    [Register("StyleWmsLayer")]
    [ArcGISRuntime.Samples.Shared.Attributes.Sample(
        name: "Style WMS layers",
        category: "Layers",
        description: "Change the style of a Web Map Service (WMS) layer.",
        instructions: "Once the layer loads, the toggle button will be enabled. Tap it to toggle between the first and second styles of the WMS layer.",
        tags: new[] { "WMS", "imagery", "styles", "visualization" })]
    public class StyleWmsLayer : UIViewController
    {
        // Hold references to UI controls.
        private MapView _myMapView;
        private UISegmentedControl _styleChoiceButton;

        // Hold the URL to the service, which has satellite imagery covering the state of Minnesota.
        private readonly Uri _wmsUrl = new Uri("https://imageserver.gisdata.mn.gov/cgi-bin/mncomp?SERVICE=WMS&VERSION=1.3.0&REQUEST=GetCapabilities");

        // Hold a list of uniquely-identifying WMS layer names to display.
        private readonly List<string> _wmsLayerNames = new List<string> {"mncomp"};

        // Hold a reference to the layer to enable re-styling.
        private WmsLayer _mnWmsLayer;

        public StyleWmsLayer()
        {
            Title = "Style WMS layers";
        }

        private async void Initialize()
        {
            try
            {
                // Create a map with spatial reference appropriate for the service.
                Map myMap = new Map(SpatialReference.Create(26915)) {MinScale = 7000000.0};

                // Create a new WMS layer displaying the specified layers from the service.
                // The default styles are chosen by default.
                _mnWmsLayer = new WmsLayer(_wmsUrl, _wmsLayerNames);

                // Wait for the layer to load.
                await _mnWmsLayer.LoadAsync();

                // Center the map on the layer's contents.
                myMap.InitialViewpoint = new Viewpoint(_mnWmsLayer.FullExtent);

                // Add the layer to the map.
                myMap.OperationalLayers.Add(_mnWmsLayer);

                // Add the map to the view.
                _myMapView.Map = myMap;

                // Enable the UI.
                _styleChoiceButton.Enabled = true;
            }
            catch (Exception ex)
            {
                new UIAlertView("Error", ex.ToString(), (IUIAlertViewDelegate) null, "OK", null).Show();
            }
        }

        private void _styleChoiceButton_ValueChanged(object sender, EventArgs e)
        {
            int styleSelection = (int) _styleChoiceButton.SelectedSegment;

            try
            {
                // Get the available styles from the first sublayer.
                IReadOnlyList<string> styles = _mnWmsLayer.Sublayers[0].SublayerInfo.Styles;

                // Apply the second style to the first sublayer.
                _mnWmsLayer.Sublayers[0].CurrentStyle = styles[styleSelection];
            }
            catch (Exception ex)
            {
                UIAlertController alert = UIAlertController.Create("Error", ex.Message, UIAlertControllerStyle.Alert);
                alert.AddAction(UIAlertAction.Create("OK", UIAlertActionStyle.Default, null));
                PresentViewController(alert, true, null);
            }
        }

        public override void ViewDidLoad()
        {
            base.ViewDidLoad();
            Initialize();
        }

        public override void LoadView()
        {
            // Create the views.
            View = new UIView() { BackgroundColor = ApplicationTheme.BackgroundColor };

            _myMapView = new MapView();
            _myMapView.TranslatesAutoresizingMaskIntoConstraints = false;

            _styleChoiceButton = new UISegmentedControl("Default", "Contrast stretch")
            {
                BackgroundColor = ApplicationTheme.BackgroundColor,
                Enabled = false,
                TranslatesAutoresizingMaskIntoConstraints = false,
                SelectedSegment = 0,
                // Clean up borders of segmented control - avoid corner pixels.
                ClipsToBounds = true,
                Layer = {CornerRadius = 5}
            };

            // Add the views.
            View.AddSubviews(_myMapView, _styleChoiceButton);

            // Lay out the views.
            NSLayoutConstraint.ActivateConstraints(new[]
            {
                _myMapView.TopAnchor.ConstraintEqualTo(View.TopAnchor),
                _myMapView.LeadingAnchor.ConstraintEqualTo(View.LeadingAnchor),
                _myMapView.TrailingAnchor.ConstraintEqualTo(View.TrailingAnchor),
                _myMapView.BottomAnchor.ConstraintEqualTo(View.BottomAnchor),

                _styleChoiceButton.LeadingAnchor.ConstraintEqualTo(View.LayoutMarginsGuide.LeadingAnchor),
                _styleChoiceButton.TrailingAnchor.ConstraintEqualTo(View.LayoutMarginsGuide.TrailingAnchor),
                _styleChoiceButton.TopAnchor.ConstraintEqualTo(View.SafeAreaLayoutGuide.TopAnchor, 8)
            });
        }

        public override void ViewWillAppear(bool animated)
        {
            base.ViewWillAppear(animated);

            // Subscribe to events.
            _styleChoiceButton.ValueChanged += _styleChoiceButton_ValueChanged;
        }

        public override void ViewDidDisappear(bool animated)
        {
            base.ViewDidDisappear(animated);

            // Unsubscribe from events, per best practice.
            _styleChoiceButton.ValueChanged -= _styleChoiceButton_ValueChanged;
        }
    }
}

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