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ArcGIS Runtime SDK for .NET

Clip geometry

This code sample is available for these platforms:
View Sample on GitHub

Clip a geometry with another geometry.

screenshot

Use case

Create a new set of geometries for analysis (e.g. displaying buffer zones around abandoned coal mine shafts in an area of planned urban development) by clipping intersecting geometries.

How to use the sample

Click the "Clip" button to clip the blue graphic with the red dashed envelopes.

How it works

  1. Use the static method GeometryEngine.Clip() to generate a clipped Geometry, passing in an existing Geometry and an Envelope as parameters. The existing geometry will be clipped where it intersects an envelope.
  2. Create a new Graphic from the clipped geometry and add it to a GraphicsOverlay on the MapView.

Relevant API

  • Envelope
  • Geometry
  • GeometryEngine.Clip
  • Graphic
  • GraphicsOverlay

Additional information

Note: the resulting geometry may be null if the envelope does not intersect the geometry being clipped.

Tags

analysis, clip, geometry

Sample Code

<UserControl
    x:Class="ArcGISRuntime.UWP.Samples.ClipGeometry.ClipGeometry"
    x:Name="_this"
    xmlns="http://schemas.microsoft.com/winfx/2006/xaml/presentation"
    xmlns:x="http://schemas.microsoft.com/winfx/2006/xaml"
    xmlns:esriUI="using:Esri.ArcGISRuntime.UI.Controls">
    <Grid>
        <esriUI:MapView x:Name="MyMapView" />
        <Border Style="{StaticResource BorderStyle}">
            <StackPanel>
                <TextBlock x:Name="ClipInstructionsLabel" 
                           Text="Click 'Clip' to clip the blue graphic with red envelopes."
                           TextWrapping="Wrap" FontWeight="SemiBold"
                           Margin="0,0,0,10"/>
                <Button x:Name="ClipButton" 
                    Content="Clip"
                        HorizontalAlignment="Stretch"
                    Click="ClipButton_Click"/>
            </StackPanel>
        </Border>
    </Grid>
</UserControl>
// 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 Esri.ArcGISRuntime.Geometry;
using Esri.ArcGISRuntime.Mapping;
using Esri.ArcGISRuntime.Symbology;
using Esri.ArcGISRuntime.UI;
using System;
using Windows.UI.Popups;
using Windows.UI.Xaml;

namespace ArcGISRuntime.UWP.Samples.ClipGeometry
{
    [ArcGISRuntime.Samples.Shared.Attributes.Sample(
        "Clip geometry",
        "Geometry",
        "This sample demonstrates how to clip a geometry with an envelope using the GeometryEngine",
        "Click the 'Clip' button to clip the blue graphic with red envelopes.",
        "")]
    public partial class ClipGeometry
    {
        // Graphics overlay to display input geometries for the clip operation.
        private GraphicsOverlay _inputGeometriesGraphicsOverlay;

        // Graphic that represents the 1st parameter of the GeometryEngine.Clip operation - it follows the boundary of Colorado.
        private Graphic _coloradoGraphic;

        // One of the graphics that represents the 2nd parameter of the GeometryEngine.Clip operation - it will be an envelope 
        // that falls completely outside the boundary of Colorado.
        private Graphic _outsideGraphic;

        // One of the graphics that represents the 2nd parameter of the GeometryEngine.Clip operation - it will be an envelope 
        // that is completely contained within the boundary of Colorado.
        private Graphic _containedGraphic;

        // One of the graphics that represents the 2nd parameter of the GeometryEngine.Clip operation - it will be an envelope 
        // that is intersects the boundary of Colorado.
        private Graphic _intersectingGraphic;

        // Graphics overlay to display the resulting geometries from the three GeometryEngine.Clip operations.
        private GraphicsOverlay _clipAreasGraphicsOverlay;

        public ClipGeometry()
        {
            InitializeComponent();

            Initialize();
        }

        private void Initialize()
        {
            // Create a new map using the WebMercator spatial reference.
            Map newMap = new Map(SpatialReferences.WebMercator)
            {
                // Set the basemap of the map to be a topographic layer.
                Basemap = Basemap.CreateTopographic()
            };

            // Create a graphics overlay to hold the input geometries for the clip operation.
            _inputGeometriesGraphicsOverlay = new GraphicsOverlay();

            // Add the input geometries graphics overlay to the MapView.
            MyMapView.GraphicsOverlays.Add(_inputGeometriesGraphicsOverlay);

            // Create a graphics overlay to hold the resulting geometries from the three GeometryEngine.Clip operations.
            _clipAreasGraphicsOverlay = new GraphicsOverlay();

            // Add the resulting geometries graphics overlay to the MapView.
            MyMapView.GraphicsOverlays.Add(_clipAreasGraphicsOverlay);

            // Create a simple line symbol for the 1st parameter of the GeometryEngine.Clip operation - it follows the 
            // boundary of Colorado.
            SimpleLineSymbol coloradoSimpleLineSymbol = new SimpleLineSymbol(
                SimpleLineSymbolStyle.Solid, System.Drawing.Color.Blue, 4);

            // Create the color that will be used as the fill for the Colorado graphic. It will be a semi-transparent, blue color.
            System.Drawing.Color coloradoFillColor = System.Drawing.Color.FromArgb(34, 0, 0, 255);

            // Create the simple fill symbol for the Colorado graphic - comprised of a fill style, fill color and outline.
            SimpleFillSymbol coloradoSimpleFillSymbol = new SimpleFillSymbol(
                SimpleFillSymbolStyle.Solid, coloradoFillColor, coloradoSimpleLineSymbol);

            // Create the geometry of the Colorado graphic.
            Envelope colorado = new Envelope(
                new MapPoint(-11362327.128340, 5012861.290274, SpatialReferences.WebMercator),
                new MapPoint(-12138232.018408, 4441198.773776, SpatialReferences.WebMercator));

            // Create the graphic for Colorado - comprised of a polygon shape and fill symbol.
            _coloradoGraphic = new Graphic(colorado, coloradoSimpleFillSymbol);

            // Add the Colorado graphic to the input geometries graphics overlay collection.
            _inputGeometriesGraphicsOverlay.Graphics.Add(_coloradoGraphic);

            // Create a simple line symbol for the three different clip geometries.
            SimpleLineSymbol clipGeomtriesSimpleLineSymbol = new SimpleLineSymbol(
                SimpleLineSymbolStyle.Dot, System.Drawing.Color.Red, 5);

            // Create an envelope outside Colorado.
            Envelope outsideEnvelope = new Envelope(
                new MapPoint(-11858344.321294, 5147942.225174, SpatialReferences.WebMercator),
                new MapPoint(-12201990.219681, 5297071.577304, SpatialReferences.WebMercator));

            // Create the graphic for an envelope outside Colorado - comprised of a polyline shape and line symbol.
            _outsideGraphic = new Graphic(outsideEnvelope, clipGeomtriesSimpleLineSymbol);

            // Add the envelope outside Colorado graphic to the graphics overlay collection.
            _inputGeometriesGraphicsOverlay.Graphics.Add(_outsideGraphic);

            // Create an envelope intersecting Colorado.
            Envelope intersectingEnvelope = new Envelope(
                new MapPoint(-11962086.479298, 4566553.881363, SpatialReferences.WebMercator),
                new MapPoint(-12260345.183558, 4332053.378376, SpatialReferences.WebMercator));

            // Create the graphic for an envelope intersecting Colorado - comprised of a polyline shape and line symbol.
            _intersectingGraphic = new Graphic(intersectingEnvelope, clipGeomtriesSimpleLineSymbol);

            // Add the envelope intersecting Colorado graphic to the graphics overlay collection.
            _inputGeometriesGraphicsOverlay.Graphics.Add(_intersectingGraphic);

            // Create a envelope inside Colorado.
            Envelope containedEnvelope = new Envelope(
                new MapPoint(-11655182.595204, 4741618.772994, SpatialReferences.WebMercator),
                new MapPoint(-11431488.567009, 4593570.068343, SpatialReferences.WebMercator));

            // Create the graphic for an envelope inside Colorado - comprised of a polyline shape and line symbol.
            _containedGraphic = new Graphic(containedEnvelope, clipGeomtriesSimpleLineSymbol);

            // Add the envelope inside Colorado graphic to the graphics overlay collection.
            _inputGeometriesGraphicsOverlay.Graphics.Add(_containedGraphic);

            // Get the extent of all of the graphics in the graphics overlay with a little padding to used as the initial zoom extent of the map.
            Geometry visibleExtent = GetExtentOfGraphicsOverlay(_inputGeometriesGraphicsOverlay, 1.3, SpatialReferences.WebMercator);

            // Set the initial visual extent of the map view to the extent of the graphics overlay.
            newMap.InitialViewpoint = new Viewpoint(visibleExtent);
            
            // Assign the map to the MapView.
            MyMapView.Map = newMap;
        }

        private Geometry GetExtentOfGraphicsOverlay(GraphicsOverlay inputGraphicsOverlay, double expansionFactor, SpatialReference spatialReferenceType)
        {
            // Get all of the graphics contained in the graphics overlay.
            GraphicCollection inputGraphicCollection = inputGraphicsOverlay.Graphics;

            // Create a new envelope builder using the same spatial reference as the graphics.
            EnvelopeBuilder unionEnvelopeBuilder = new EnvelopeBuilder(spatialReferenceType);

            // Loop through each graphic in the graphic collection.
            foreach (Graphic oneGraphic in inputGraphicCollection)
            {
                // Union the extent of each graphic in the envelope builder.
                unionEnvelopeBuilder.UnionOf(oneGraphic.Geometry.Extent);
            }

            // Expand the envelope builder by the expansion factor.
            unionEnvelopeBuilder.Expand(expansionFactor);

            // Return the unioned extent plus the expansion factor.
            return unionEnvelopeBuilder.Extent;
        }

        private async void ClipButton_Click(object sender, RoutedEventArgs e)
        {
            try
            {
                // Remove the Colorado graphic from the input geometries graphics overlay collection. That way it will be easier 
                // to see the clip versions of the GeometryEngine.Clip operation. 
                _inputGeometriesGraphicsOverlay.Graphics.Remove(_coloradoGraphic);

                // Loop through each graphic in the input geometries for the clip operation.
                foreach (Graphic oneGraphic in _inputGeometriesGraphicsOverlay.Graphics)
                {
                    // Perform the clip operation. The first parameter of the clip operation will always be the Colorado graphic. 
                    // The second parameter of the clip operation will be one of the 3 different clip geometries (_outsideGraphic, 
                    // _containedGraphic, or _intersectingGraphic).
                    Geometry myGeometry = GeometryEngine.Clip(_coloradoGraphic.Geometry, (Envelope)oneGraphic.Geometry);

                    // Only work on returned geometries that are not null.
                    if (myGeometry != null)
                    {
                        // Create the graphic as a result of the clip operation using the same symbology that was defined for 
                        // the _coloradoGraphic defined in the Initialize() method previously. 
                        Graphic clippedGraphic = new Graphic(myGeometry, _coloradoGraphic.Symbol);

                        // Add the clipped graphic to the clip areas graphics overlay collection.
                        _clipAreasGraphicsOverlay.Graphics.Add(clippedGraphic);
                    }
                }

                // Disable the button after has been used.
                ClipButton.IsEnabled = false;
            }
            catch (System.Exception ex)
            {
                // Display an error message if there is a problem generating clip operation.
                MessageDialog theMessageDialog = new MessageDialog("Geometry Engine Failed: " + ex.Message);
                await theMessageDialog.ShowAsync();
            }
        }
    }
}