All docs
V20.1
20.1
19.2
19.1
The page you are viewing does not exist in version 19.1. This link will take you to the root page.
18.2
The page you are viewing does not exist in version 18.2. This link will take you to the root page.
18.1
The page you are viewing does not exist in version 18.1. This link will take you to the root page.
17.2
The page you are viewing does not exist in version 17.2. This link will take you to the root page.

HeatmapDensityBasedAlgorithm Class

The algorithm that allows the Map Control to plot a heatmap based on the density of heatmap points.

Namespace: DevExpress.XtraMap

Assembly: DevExpress.XtraMap.v20.1.dll

Declaration

public class HeatmapDensityBasedAlgorithm :
    HeatmapAlgorithmBase,
    IDensityBasedAlgorithm,
    IHeatmapAlgorithm
Public Class HeatmapDensityBasedAlgorithm
    Inherits HeatmapAlgorithmBase
    Implements IDensityBasedAlgorithm,
               IHeatmapAlgorithm

Remarks

When you use the HeatmapDensityBasedAlgorithm to create a heatmap, the Map Control aggregates points into areas of different colors. An area with high point density is painted red. A green area indicates that this region contains a low number of points. The Map Control re-aggregates heatmap points when you zoom in/out a map. For this reason, areas of aggregated points can change their colors.

To change the predefined color scheme, specify the HeatmapProvider.Colorizer property. The first item in the ChoroplethColorizer.ColorItems collection defines a color for areas with low point density, the last item specifies the color of areas with high point density.

Examples

This example shows how to create a heatmap layer for the Map Control.

using DevExpress.XtraMap;
using System;
using System.Data;
using System.Drawing;
using System.Windows.Forms;

namespace HeatMapSample {
    public partial class Form1 : Form {
        public Form1() {
            InitializeComponent();
        }
        private void Form1_Load(object sender, EventArgs e) {

            ImageLayer bingLayer = new ImageLayer();
            bingLayer.DataProvider = new BingMapDataProvider { BingKey = "Your Bing Maps key here." };
            mapControl1.Layers.Add(bingLayer);

            ChoroplethColorizer colorizer = new ChoroplethColorizer();
            colorizer.RangeStops.AddRange(new double[] { 0.1, 0.2, 0.7, 1 });
            colorizer.ColorItems.Add(new ColorizerColorItem(Color.FromArgb(50, 128, 255, 0)));
            colorizer.ColorItems.Add(new ColorizerColorItem(Color.FromArgb(255, 255, 255, 0)));
            colorizer.ColorItems.Add(new ColorizerColorItem(Color.FromArgb(255, 234, 72, 58)));
            colorizer.ColorItems.Add(new ColorizerColorItem(Color.FromArgb(255, 162, 36, 25)));
            colorizer.ApproximateColors = true;

            HeatmapDataSourceAdapter adapter = new HeatmapDataSourceAdapter();
            adapter.Mappings.XCoordinate = "glon"; // The data source field name that provides x-coordinates.
            adapter.Mappings.YCoordinate = "glat"; // The data source field name that provides y-coordinates.
            adapter.DataSource = LoadData("../../Data/Earthquakes.xml", "Row");

            HeatmapProvider provider = new HeatmapProvider();
            provider.PointSource = adapter;
            provider.Algorithm = new HeatmapDensityBasedAlgorithm { PointRadius = 8 };
            provider.Colorizer = colorizer;

            ImageLayer heatmapLayer = new ImageLayer();
            heatmapLayer.DataProvider = provider;
            mapControl1.Layers.Add(heatmapLayer);

            ColorScaleLegend legend = new ColorScaleLegend();
            legend.Header = "Seismic Density";
            legend.EnableGradientScale = true;
            legend.Layer = heatmapLayer;
            legend.HeaderStyle.Font = new Font("Tahoma", 12F);
            mapControl1.Legends.Add(legend);
        }
        DataTable LoadData(string filePath, string tableName) {
            DataSet xmlDataSet = new DataSet("XML DataSet");
            xmlDataSet.ReadXml(filePath);
            return xmlDataSet.Tables[tableName];
        }
    }
}

Inheritance

Object
HeatmapAlgorithmBase
HeatmapDensityBasedAlgorithm
See Also