基于ArcEngine进行地物分类景观指数计算

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我是靠谱客的博主直率保温杯，最近开发中收集的这篇文章主要介绍基于ArcEngine进行地物分类景观指数计算，觉得挺不错的，现在分享给大家，希望可以做个参考。

概述

前两天写了一个对地物分类进行景观评价的小工具，采用ArcEngine实现，在此备忘一下，仅供学习参考.

核心过程如下：根据评价尺度大小分块获取影响，分别对各个分块进行地物统计，计算景观指数，将该得分保存在分块中心点位置.


// rst
: 原始地物分类影像
// patchSize
: 分块大小，正方形边长，为该计算单元包含像元个数
// shpFile
: 结果保存路径，点状要素类，保存为ShpeFile文件
private void runModel(Raster rst, int patchSize, string shpFile)
{
#region 准备工作
// 获取背景值
dynamic nodata = ((rst as IRasterBandCollection).Item(0) as IRasterProps).NoDataValue;
appendMessage("tNodataValue = " + nodata);
// 初始化分块辅助工具
var rstProps = rst as IRasterProps;
var pixelSize = rstProps.MeanCellSize();
var rstExt = rstProps.Extent;
var pbHelper = new PixelBlockHelper(rstProps.Width, rstProps.Height,pixelSize.X, pixelSize.Y,
rstExt.XMin, rstExt.XMax, rstExt.YMin, rstExt.YMax);
long pbCount = pbHelper.GetCount(patchSize);
int pbCols = pbHelper.GetColumns(patchSize);
int pbRows = pbHelper.GetRows(patchSize);
appendMessage("tPatch Number : " + pbRows + "(Row) X " + pbCols + "(Col) = " + pbCount);
// 初始化分块游标
IRaster2 rst2 = rst as IRaster2;
var patchCursor = rst2.CreateCursorEx(new Pnt() { X = patchSize, Y = patchSize });
// 创建shapefile文件并开启编辑状态
var scoreName = "pjz";
var resultShp = CommonFuns.pointShp(shpFile, rstProps.SpatialReference, scoreName);
IFeatureClassWrite shpWriter = resultShp as IFeatureClassWrite;
IWorkspaceEdit shpWpsEdit = (shpWriter as IDataset).Workspace as IWorkspaceEdit;
shpWpsEdit.StartEditing(true);
shpWpsEdit.StartEditOperation();
var scoreFieldIndex = resultShp.FindField(scoreName);
// 进度指示器
long doneStep = pbCount / 10;
// 每隔 10% 播报进度
long doneCount = 0;
// 当前进度
GeoLandEvaluator glEvaluator = new GeoLandEvaluator();
// 初始化地物评价工具
IFeature resultFeature;
// 评价结果要素
#endregion
#region 地物景观指数计算
ESRI.ArcGIS.esriSystem.ISet featureSet = new ESRI.ArcGIS.esriSystem.Set();
do
{
glEvaluator.Reset();
// 重置评价工具
var block = patchCursor.PixelBlock as IPixelBlock3;
dynamic lands = block.get_PixelData(0);
// 获取分快像元值，System.Array
for (int x = 0; x < block.Width; x++)
// 扫描像元值填充入评价工具，过滤背景值
{
for (int y = 0; y < block.Height; y++)
{
dynamic landType = lands.GetValue(x, y);
if (nodata != landType) glEvaluator.AddLand((int)landType);
}
}
var score = glEvaluator.Score();
// 计算得分
var tl = patchCursor.TopLeft;
// 计算中心点位置
var cxy = pbHelper.GetCenter(tl.X, tl.Y, patchSize);
// 保存计算结果,播报进度
resultFeature = resultShp.CreateFeature();
resultFeature.Shape = new ESRI.ArcGIS.Geometry.Point()
{
X = cxy[0],
Y = cxy[1]
};
resultFeature.set_Value(scoreFieldIndex, score);
featureSet.Add(resultFeature);
doneCount++;
if (doneCount % doneStep == 0)
{
shpWriter.WriteFeatures(featureSet);
featureSet.RemoveAll();
appendMessage("t...
" + (100.0 * doneCount / pbCount) + " %
...");
}
} while (patchCursor.Next());
shpWriter.WriteFeatures(featureSet);
featureSet.RemoveAll();
#endregion
// 关闭编辑状态，保存数据
shpWpsEdit.StopEditOperation();
shpWpsEdit.StopEditing(true);
appendMessage("<< Finished! ");
}

地物评价工具工作过程为：统计分块内各种类型的地物面积大小，计算各类地物的百分比 Pi ，采用如下公式计算景观指数得分——

score = -（P1＊ln(P1)+P2*ln(P2)+...+Pn*ln(Pn)）

using System;
using System.Collections.Generic;
namespace ...
{
/// <summary>
/// 地物类别统计评估工具
/// </summary>
public class GeoLandEvaluator
{
/// <summary>
/// 地物分类计数器
/// </summary>
private IDictionary<int, long> landCounter = null;
/// <summary>
/// 地物总数
/// </summary>
private long landSum = 0;
public GeoLandEvaluator()
{
landCounter = new Dictionary<int, long>();
Reset();
}
/// <summary>
/// 重置地物统计评估工具
/// </summary>
public void Reset()
{
if (landCounter != null) landCounter.Clear();
landSum = 0;
}
/// <summary>
/// 添加分类
/// </summary>
public void AddLand(int landType)
{
if (landCounter.ContainsKey(landType))
{
landCounter[landType]++;
}
else
{
landCounter.Add(landType, 1);
}
landSum++;
}
/// <summary>
/// 添加地物分类
/// </summary>
public void AddLand(int[] landTypes)
{
foreach (int ldType in landTypes)
{
AddLand(ldType);
}
}
/// <summary>
/// 计算景观指数评价值
/// </summary>
/// <returns></returns>
public double Score()
{
if (landCounter == null || landCounter.Count < 1) return 0;
double score = 0.0;
foreach (long ldCount in landCounter.Values)
{
double per = 1.0 * ldCount / landSum;
score += per * Math.Log(per, Math.E);
}
return score * (-1.0);
}
}
}

栅格像元分块辅助工具

using System;
namespace ...
{
/// <summary>
/// 栅格像元分块辅助工具
/// </summary>
public class PixelBlockHelper
{
public double PixelWidth { get; private set; }
public double PixelHeight { get; private set; }
public int RstWidth { get; private set; }
public int RstHeight { get; private set; }
public double RstXMin { get; private set; }
public double RstYMin { get; private set; }
public double RstXMax { get; private set; }
public double RstYMax { get; private set; }
public PixelBlockHelper(int rstWidth, int rstHeight,double pixelWidth, double pixelHeight,
double rstXmin, double rstXmax, double rstYmin, double rstYmax)
{
this.RstWidth = rstWidth;
this.RstHeight = rstHeight;
this.PixelWidth = pixelWidth;
this.PixelHeight = pixelHeight;
this.RstXMin = rstXmin;
this.RstXMax = rstXmax;
this.RstYMin = rstYmin;
this.RstYMax = rstYmax;
}
/// <summary>
/// 计算 分块 中心坐标 ， 计算原点为影像（可视）左上角
/// </summary>
/// <param name="xOffset">左上角横轴偏移量</param>
/// <param name="yOffset">左上角纵轴偏移量</param>
/// <param name="blockSize">正方形分块大小，边长</param>
/// <returns>分块中心点 地图坐标</returns>
public double[] GetCenter(double xOffset, double yOffset, int blockSize)
{
double[] xyOffset = new double[] { xOffset, yOffset };
return GetCenter(xyOffset, blockSize);
}
/// <summary>
/// 计算 分块 中心坐标 ， 计算原点为影像（可视）左上角
/// </summary>
/// <param name="xyOffset">左上角偏移量，[x,y]</param>
/// <param name="blockSize">正方形分块大小，边长</param>
/// <returns>分块中心点 地图坐标</returns>
public double[] GetCenter(double[] xyOffset, int blockSize)
{
xyOffset[0] = PixelWidth * (xyOffset[0] + blockSize / 2.0) + RstXMin;
xyOffset[1] = RstYMax - PixelHeight * (xyOffset[1] + blockSize / 2.0);
return xyOffset;
}
/// <summary>
/// 计算分块 总数
/// </summary>
/// <returns>可划分的大小为 blockSize 的正方形分块总数</returns>
public long GetCount(int blockSize)
{
return (long)GetColumns(blockSize) * GetRows(blockSize);
}
/// <summary>
/// 计算X方向 分块 列数
/// </summary>
/// <returns>以blockSize为间隔可划分的列数</returns>
public int GetColumns(int blockSize)
{
return (int)Math.Ceiling((double)(this.RstWidth) / blockSize);
}
/// <summary>
/// 计算 Y方向 分块 行数
/// </summary>
/// <returns>以blockSize为间隔可划分的行数</returns>
public int GetRows(int blockSize)
{
return (int)Math.Ceiling((double)(this.RstHeight) / blockSize);
}
}
}

创建Shpefile文件核心代码如下：

/// <summary>
/// 创建 点 Shapefile
/// </summary>
/// <param name="shpFile">完整的保存路径</param>
/// <param name="spatialRef">参考坐标系</param>
/// <param name="scoreName">属性值字段名称（double类型字段），默认为 pjz</param>
/// <returns>包含字段类型为double名称为scoreName的shapefile要素类</returns>
public static IFeatureClass pointShp(string shpFile, ISpatialReference spatialRef, string scoreName = "pjz")
{
FileInfo fi = new FileInfo(shpFile);
var wpsDir = fi.DirectoryName;
// shapefile保存目录
var shapeFiledName = "Shape";
var fidFieldName = "FID";
if (string.IsNullOrEmpty(scoreName)) scoreName = "pjz";
//
var factory = new ShapefileWorkspaceFactory() as IWorkspaceFactory;
var shpWps = (IFeatureWorkspace)factory.OpenFromFile(wpsDir, 0);
// prepare fileds for the shapefile
Fields fieldCollection = new Fields();
IFieldsEdit fieldCollectionEdit = fieldCollection as IFieldsEdit;
// 设置FID
Field field = new Field();
IFieldEdit fieldEdit = field as IFieldEdit;
fieldEdit.Name_2 = fidFieldName;
fieldEdit.Type_2 = esriFieldType.esriFieldTypeOID;
fieldCollectionEdit.AddField(field);
// 设置几何类型字段
field = new Field();
fieldEdit = field as IFieldEdit;
fieldEdit.Name_2 = shapeFiledName;
fieldEdit.Type_2 = esriFieldType.esriFieldTypeGeometry;
GeometryDef geoDef = new GeometryDef();
IGeometryDefEdit geoDefEdit = geoDef as IGeometryDefEdit;
geoDefEdit.GeometryType_2 = esriGeometryType.esriGeometryPoint;
geoDefEdit.SpatialReference_2 = spatialRef;
fieldEdit.GeometryDef_2 = geoDef;
fieldCollectionEdit.AddField(field);
// 设置景观指数评价值字段
field = new Field();
fieldEdit = field as IFieldEdit;
fieldEdit.Name_2 = scoreName;
fieldEdit.Type_2 = esriFieldType.esriFieldTypeDouble;
fieldCollectionEdit.AddField(field);
//
var shp = shpWps.CreateFeatureClass(fi.Name, fieldCollection, null, null,
esriFeatureType.esriFTSimple,shapeFiledName, string.Empty);
return shp;
}

直接上图吧～