Clip geometry

View on GitHub
Sample viewer app

Clip a geometry with another geometry.

Image of clip geometry

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

Tap the button to clip the blue graphic with the red dashed envelopes.

How it works

  1. Use the static method class AGSGeometryEngine.clipGeometry(_:with:) to generate a clipped AGSGeometry, passing in an existing AGSGeometry and an AGSEnvelope as parameters. The existing geometry will be clipped where it intersects an envelope.
  2. Create a new AGSGraphic from the clipped geometry and add it to an AGSGraphicsOverlay on the AGSMapView.

Relevant API

  • AGSEnvelope
  • AGSGeometry
  • AGSGraphic
  • AGSGraphicsOverlay
  • class AGSGeometryEngine.clipGeometry(_:with:)

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

ClipGeometryViewController.swift
                                                                                                                                      
1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
34
35
36
37
38
39
40
41
42
43
44
45
46
47
48
49
50
51
52
53
54
55
56
57
58
59
60
61
62
63
64
65
66
67
68
69
70
71
72
73
74
75
76
77
78
79
80
81
82
83
84
85
86
87
88
89
90
91
92
93
94
95
96
97
98
99
100
101
102
103
104
105
106
107
108
109
110
111
112
113
114
115
116
117
118
119
120
121
122
123
124
125
126
127
128
129
130
131
132
133
134
// 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.

import UIKit
import ArcGIS

class ClipGeometryViewController: UIViewController {
    @IBOutlet weak var mapView: AGSMapView!

    /// The overlay for displaying the graphic of Colorado.
    private let coloradoOverlay = AGSGraphicsOverlay()

    /// The overlay for displaying the other envelopes.
    private let envelopesOverlay: AGSGraphicsOverlay = {
        /// An envelope outside Colorado.
        let outsideEnvelope = AGSEnvelope(
            xMin: -11858344.321294,
            yMin: 5147942.225174,
            xMax: -12201990.219681,
            yMax: 5297071.577304,
            spatialReference: .webMercator()
        )

        /// An envelope intersecting Colorado.
        let intersectingEnvelope = AGSEnvelope(
            xMin: -11962086.479298,
            yMin: 4566553.881363,
            xMax: -12260345.183558,
            yMax: 4332053.378376,
            spatialReference: .webMercator()
        )

        /// An envelope inside Colorado.
        let containedEnvelope = AGSEnvelope(
            xMin: -11655182.595204,
            yMin: 4741618.772994,
            xMax: -11431488.567009,
            yMax: 4593570.068343,
            spatialReference: .webMercator()
        )

        /// A dotted red outline symbol.
        let redOutline = AGSSimpleLineSymbol(style: .dot, color: .red, width: 3)

        /// The envelopes in the order we want to display them.
        let envelopes = [outsideEnvelope, intersectingEnvelope, containedEnvelope]

        /// The graphics for the envelopes with the red outline symbol.
        let graphics = envelopes.map { AGSGraphic(geometry: $0, symbol: redOutline) }

        let envelopesOverlay = AGSGraphicsOverlay()
        // add the graphics to the overlay
        envelopesOverlay.graphics.addObjects(from: graphics)
        return envelopesOverlay
    }()

    /// The graphic representing Colorado.
    private let coloradoGraphic: AGSGraphic = {
        /// An envelope approximating the boundary of Colorado.
        let coloradoGeometry = AGSEnvelope(
            xMin: -11362327.128340,
            yMin: 5012861.290274,
            xMax: -12138232.018408,
            yMax: 4441198.773776,
            spatialReference: .webMercator())

        /// A semi-transparent blue color for the fill.
        let fillColor = UIColor.blue.withAlphaComponent(0.2)
        /// The fill symbol for displaying Colorado.
        let fillSymbol = AGSSimpleFillSymbol(
            style: .solid,
            color: fillColor,
            outline: AGSSimpleLineSymbol(style: .solid, color: .blue, width: 2)
        )
        // create a graphic from the geometry and symbol
        return AGSGraphic(geometry: coloradoGeometry, symbol: fillSymbol)
    }()

    override func viewDidLoad() {
        super.viewDidLoad()

        // add the source code button item to the right of navigation bar
        (navigationItem.rightBarButtonItem as! SourceCodeBarButtonItem).filenames = ["ClipGeometryViewController"]

        // instantiate map using a basemap
        let map = AGSMap(basemapStyle: .arcGISTopographic)
        // assign the map to the map view
        mapView.map = map

        // add the Colorado graphic to its overlay
        coloradoOverlay.graphics.add(coloradoGraphic)

        // add the graphics overlays to the map view in the order we want them to appear
        mapView.graphicsOverlays.addObjects(from: [coloradoOverlay, envelopesOverlay])

        // set the initial viewpoint to the extent of the Colorado geometry, plus a margin
        mapView.setViewpointGeometry(coloradoGraphic.geometry!, padding: 100)
    }

    @IBAction func clipGeometry(_ sender: UIBarButtonItem) {
        // disable the clip button
        sender.isEnabled = false

        // hide the Colorado graphic
        coloradoGraphic.isVisible = false

        guard let coloradoGeometry = coloradoGraphic.geometry,
            let coloradoSymbol = coloradoGraphic.symbol else {
            return
        }

        for envelopeGraphic in envelopesOverlay.graphics as! [AGSGraphic] {
            if let envelope = envelopeGraphic.geometry as? AGSEnvelope,
                // use the geometry engine to get a new geometry for the area of Colorado that overlaps the envelope
                let clippedGeometry = AGSGeometryEngine.clipGeometry(coloradoGeometry, with: envelope) {
                // if there is an overlap, greate a graphic for it using the same symbol as Colorado
                let clippedGraphic = AGSGraphic(geometry: clippedGeometry, symbol: coloradoSymbol)
                // add the resultant graphic to the overlay
                coloradoOverlay.graphics.add(clippedGraphic)
            }
        }
    }
}

Your browser is no longer supported. Please upgrade your browser for the best experience. See our browser deprecation post for more details.