Segmentation.cs

This example demonstrates how to do a segmentation of layers by regular grid, to calculate the percentage of land usage for each cell and to show it as pie charts. The combined extents of 2 polygon shapefiles are split by regular grid with 4 by 4 cells, which is represented by polygon shapefile. An intersection for each cell of grid and each input shapefile is calculated.To visualize the relative area of polygons obtained by intersection a temporary shapefile with charts is created. Each chart denote the percentage of area covered by one of the input shapefiles in the given cell. Note: the grid mentioned in this example has nothing to do with Grid class provided by MapWinGIS. The displayed areas are represented in hectars. Here is a screenshot with the results of the code.

using System;
using System.Windows.Forms;
using AxMapWinGIS;
using MapWinGIS;
using System.IO;
using System.Collections.Generic;

public partial class MapExamples
{
    // <summary>
    // Performs a segmentation of shapes by regular grid
    // </summary>
    public void Segmentation(AxMap axMap1, string dataPath)
    {
        string[] filenames = new string[2];
        filenames[0] = dataPath + "natural.shp";
        filenames[1] = dataPath + "landuse.shp";

        if (!File.Exists(filenames[0]) || !File.Exists(filenames[1]))
        {
            MessageBox.Show("Couldn't file the files (natural.shp, landuse.shp): " + dataPath);
            return;
        }

        List<Shapefile> layers = new List<Shapefile>();

        for (int i = 0; i < filenames.Length; i++)
        {
            Shapefile sf = new Shapefile();
            sf.Open(filenames[i], null);
            layers.Add(sf);
            axMap1.AddLayer(layers[i], true);
        }

        int count = 4;
        Extents ext = axMap1.MaxExtents as Extents;
        double xStep = (ext.xMax - ext.xMin)/count;
        double yStep = (ext.yMax - ext.yMin)/count;

        Shapefile sfGrid = new Shapefile();
        sfGrid.CreateNewWithShapeID("", ShpfileType.SHP_POLYGON);
        sfGrid.GeoProjection.CopyFrom(layers[0].GeoProjection);

        ColorScheme scheme = new ColorScheme();
        scheme.SetColors2(tkMapColor.Orange, tkMapColor.Yellow);

        for (int i = 0; i < layers.Count; i++)
        {
            string name = Path.GetFileNameWithoutExtension(layers[i].Filename);
            int fieldIndex = sfGrid.EditAddField(name, FieldType.DOUBLE_FIELD, 10, 12);
            uint color = scheme.get_GraduatedColor((i + 1) / layers.Count);
            sfGrid.Charts.AddField2(fieldIndex, color);
        }

        for (int i = 0; i < count; i++)
        {
            for (int j = 0; j < count; j++)
            {
                Shape shp = new Shape();
                shp.Create(ShpfileType.SHP_POLYGON);
                shp.AddPoint(ext.xMin + i * xStep, ext.yMin + j * yStep);
                shp.AddPoint(ext.xMin + i * xStep, ext.yMin + (j + 1) * yStep);
                shp.AddPoint(ext.xMin + (i + 1) * xStep, ext.yMin + (j + 1) * yStep);
                shp.AddPoint(ext.xMin + (i + 1) * xStep, ext.yMin + j * yStep);
                shp.AddPoint(ext.xMin + i * xStep, ext.yMin + j * yStep);
                int shapeIndex = sfGrid.EditAddShape(shp);

                for (int layer = 0; layer < layers.Count; layer++)
                {
                    Shapefile sf = layers[layer];
                    double area = 0.0;
                    for (int n = 0; n < sf.NumShapes; n++)
                    {
                        Shape shp2 = sf.get_Shape(n);
                        if (shp.Intersects(shp2))
                        {
                            Shape shpResult = shp2.Clip(shp, tkClipOperation.clIntersection);
                            if (shpResult != null)
                            {
                                area += shpResult.Area;
                            }
                        }
                    }

                    // divide by 10000.0 to convert square meters to hectars
                    bool success = sfGrid.EditCellValue(layer + 1, shapeIndex, area/10000.0);   
                }
            }
        }

        // generating charts
        Charts charts = sfGrid.Charts;
        charts.Generate(tkLabelPositioning.lpCenter);
        charts.ChartType = tkChartType.chtPieChart;
        charts.PieRadius = 18;
        charts.Thickness = 10;
        charts.ValuesVisible = true;
        charts.Visible = true;

        ShapeDrawingOptions options = sfGrid.DefaultDrawingOptions;
        options.FillVisible = false;
        options.LineWidth = 2;
        options.LineStipple = tkDashStyle.dsDash;
        options.LineColor = 255;

        axMap1.AddLayer(sfGrid, true);
        axMap1.ZoomToMaxExtents();
    }
}