How to: Colorize Map Contours Using the Graph Colorizer

• Nov 13, 2018
• 3 minutes to read

This example demonstrates how to paint map contours loaded from a Shapefile (Countries.shp) using the graph colorizer.

To accomplish this task, create a graph colorizer (the GraphColorizer object) and assign it to the VectorItemsLayer.Colorizer property.

Then, specify the desired set of colors in the GenericColorizerItemCollection<T> object that is accessed via the GraphColorizer.ColorItems property.

View Example

Form1.cs

using System;
using System.Collections.Generic;
using System.Drawing;
using System.Windows.Forms;
using DevExpress.XtraMap;

namespace MapGraphColorizer {
    public partial class Form1 : Form {
        public Form1() {
            InitializeComponent();
        }

        private void Form1_Load(object sender, EventArgs e) {

            // Create a map control and specify its dock style.
            MapControl map = new MapControl();
            map.Dock = DockStyle.Fill;

            // Specify the map's initial view.  
            map.ZoomLevel = 2;
            map.CenterPoint = new GeoPoint(38, -100);

            // Create a file layer and assign a shape loader to it.
            map.Layers.Add(new VectorItemsLayer() {
                Data = CreateData(),
                Colorizer = CreateColorizer()
            });

            // Add the map control to the window. 
            this.Controls.Add(map);
        }

        private IMapDataAdapter CreateData() {
            // Create an object to load data from a shapefile.
            ShapefileDataAdapter loader = new ShapefileDataAdapter();

            // Determine the path to the Shapefile.
            Uri baseUri = new Uri(System.Reflection.Assembly.GetEntryAssembly().Location);
            string shapefilePath = "../../Data/Countries.shp";
            loader.FileUri = new Uri(baseUri, shapefilePath);

            return loader;
        }

        private MapColorizer CreateColorizer() {
            // Create a graph colorizer.
            GraphColorizer colorizer = new GraphColorizer();

            // Specify colors for the colorizer.
            colorizer.ColorItems.AddRange(new List<ColorizerColorItem> { 
                new ColorizerColorItem(Color.FromArgb(0xF1, 0xC1, 0x49)), 
                new ColorizerColorItem(Color.FromArgb(0xE5, 0xA8, 0x4D)),
                new ColorizerColorItem(Color.FromArgb(0xC5, 0x64, 0x50)),
                new ColorizerColorItem(Color.FromArgb(0xD6, 0x86, 0x4E)),
                new ColorizerColorItem(Color.FromArgb(0x79, 0x96, 0x89)), 
                new ColorizerColorItem(Color.FromArgb(0xA2, 0xA8, 0x75))
            });
            return colorizer;
        }
    }
}

Form1.vb

Imports System
Imports System.Collections.Generic
Imports System.Drawing
Imports System.Windows.Forms
Imports DevExpress.XtraMap

Namespace MapGraphColorizer
    Partial Public Class Form1
        Inherits Form

        Public Sub New()
            InitializeComponent()
        End Sub

        Private Sub Form1_Load(ByVal sender As Object, ByVal e As EventArgs) Handles MyBase.Load

            ' Create a map control and specify its dock style.
            Dim map As New MapControl()
            map.Dock = DockStyle.Fill

            ' Specify the map's initial view.  
            map.ZoomLevel = 2
            map.CenterPoint = New GeoPoint(38, -100)

            ' Create a file layer and assign a shape loader to it.
            map.Layers.Add(New VectorItemsLayer() With {.Data = CreateData(), .Colorizer = CreateColorizer()})

            ' Add the map control to the window. 
            Me.Controls.Add(map)
        End Sub

        Private Function CreateData() As IMapDataAdapter
            ' Create an object to load data from a shapefile.
            Dim loader As New ShapefileDataAdapter()

            ' Determine the path to the Shapefile.
            Dim baseUri As New Uri(System.Reflection.Assembly.GetEntryAssembly().Location)
            Dim shapefilePath As String = "../../Data/Countries.shp"
            loader.FileUri = New Uri(baseUri, shapefilePath)

            Return loader
        End Function

        Private Function CreateColorizer() As MapColorizer
            ' Create a graph colorizer.
            Dim colorizer As New GraphColorizer()

            ' Specify colors for the colorizer.
            colorizer.ColorItems.AddRange(New List(Of ColorizerColorItem) From { _
                New ColorizerColorItem(Color.FromArgb(&HF1, &HC1, &H49)), _
                New ColorizerColorItem(Color.FromArgb(&HE5, &HA8, &H4D)), _
                New ColorizerColorItem(Color.FromArgb(&HC5, &H64, &H50)), _
                New ColorizerColorItem(Color.FromArgb(&HD6, &H86, &H4E)), _
                New ColorizerColorItem(Color.FromArgb(&H79, &H96, &H89)), _
                New ColorizerColorItem(Color.FromArgb(&HA2, &HA8, &H75)) _
            })
            Return colorizer
        End Function
    End Class
End Namespace