第09章：C#/.NET绑定开发指南
9.1 .NET GDAL 简介
9.1.1 概述
GDAL 为 .NET 平台提供了完整的绑定支持，允许 C# 开发者在 Windows 和跨平台环境中使用 GDAL 的全部功能。.NET GDAL 绑定特别适合企业级 Windows 应用开发。
┌─────────────────────────────────────────────────────────────┐
│ .NET GDAL 架构 │
├─────────────────────────────────────────────────────────────┤
│ │
│ ┌─────────────────────────────────────────────────────┐ │
│ │ .NET 应用层 │ │
│ │ WPF/WinForms │ ASP.NET │ 控制台应用 │ │
│ └─────────────────────────────────────────────────────┘ │
│ │ │
│ ▼ │
│ ┌─────────────────────────────────────────────────────┐ │
│ │ GDAL .NET 绑定 │ │
│ │ OSGeo.GDAL │ OSGeo.OGR │ OSGeo.OSR │ │
│ └─────────────────────────────────────────────────────┘ │
│ │ │
│ ▼ P/Invoke │
│ ┌─────────────────────────────────────────────────────┐ │
│ │ GDAL 本地库 (C/C++) │ │
│ └─────────────────────────────────────────────────────┘ │
│ │
└─────────────────────────────────────────────────────────────┘
9.1.2 可用的 NuGet 包
| 包名 | 描述 | 平台支持 |
|---|---|---|
| MaxRev.Gdal.Universal | 自动配置，跨平台支持 | Windows, Linux, macOS |
| MaxRev.Gdal.WindowsRuntime.Minimal | Windows 最小运行时 | Windows |
| MaxRev.Gdal.LinuxRuntime.Minimal | Linux 最小运行时 | Linux |
| GDAL.Native | 官方原生包 | 平台特定 |
9.2 环境配置
9.2.1 创建项目
# 创建新项目
dotnet new console -n GdalDemo -f net6.0
cd GdalDemo# 添加 NuGet 包
dotnet add package MaxRev.Gdal.Universal
9.2.2 项目文件配置
<!-- GdalDemo.csproj -->
<Project Sdk="Microsoft.NET.Sdk"><PropertyGroup><OutputType>Exe</OutputType><TargetFramework>net6.0</TargetFramework><ImplicitUsings>enable</ImplicitUsings><Nullable>enable</Nullable></PropertyGroup><ItemGroup><PackageReference Include="MaxRev.Gdal.Universal" Version="3.7.0.100" /></ItemGroup></Project>
9.2.3 初始化 GDAL
using MaxRev.Gdal.Core;
using OSGeo.GDAL;
using OSGeo.OGR;
using OSGeo.OSR;namespace GdalDemo;/// <summary>
/// GDAL 初始化帮助类
/// </summary>
public static class GdalInitializer
{private static bool _initialized = false;private static readonly object _lock = new object();/// <summary>/// 初始化 GDAL/// </summary>public static void Initialize(){if (_initialized) return;lock (_lock){if (_initialized) return;// 使用 MaxRev.Gdal 自动配置GdalBase.ConfigureAll();// 可选：设置配置选项Gdal.SetConfigOption("GDAL_FILENAME_IS_UTF8", "YES");Gdal.SetConfigOption("SHAPE_ENCODING", "UTF-8");// 打印版本信息Console.WriteLine($"GDAL 版本: {Gdal.VersionInfo("VERSION_NUM")}");Console.WriteLine($"栅格驱动数: {Gdal.GetDriverCount()}");Console.WriteLine($"矢量驱动数: {Ogr.GetDriverCount()}");_initialized = true;}}/// <summary>/// 列出所有驱动/// </summary>public static void ListDrivers(){Initialize();Console.WriteLine("\n栅格驱动:");for (int i = 0; i < Gdal.GetDriverCount(); i++){using var driver = Gdal.GetDriver(i);Console.WriteLine($" {driver.ShortName}: {driver.LongName}");}Console.WriteLine("\n矢量驱动:");for (int i = 0; i < Ogr.GetDriverCount(); i++){using var driver = Ogr.GetDriver(i);Console.WriteLine($" {driver.GetName()}");}}
}
9.3 栅格数据处理
9.3.1 读取栅格数据
using OSGeo.GDAL;
using OSGeo.OSR;namespace GdalDemo.Raster;/// <summary>
/// 栅格数据读取器
/// </summary>
public class RasterReader
{/// <summary>/// 读取栅格数据信息/// </summary>public static void ReadRasterInfo(string filepath){GdalInitializer.Initialize();using var ds = Gdal.Open(filepath, Access.GA_ReadOnly);if (ds == null){Console.WriteLine($"无法打开文件: {filepath}");return;}// 基本信息Console.WriteLine($"文件: {ds.GetDescription()}");Console.WriteLine($"驱动: {ds.GetDriver().ShortName}");Console.WriteLine($"尺寸: {ds.RasterXSize} x {ds.RasterYSize}");Console.WriteLine($"波段数: {ds.RasterCount}");// 地理变换double[] geoTransform = new double[6];ds.GetGeoTransform(geoTransform);Console.WriteLine($"原点: ({geoTransform[0]}, {geoTransform[3]})");Console.WriteLine($"像素大小: ({geoTransform[1]}, {geoTransform[5]})");// 投影信息string projection = ds.GetProjection();if (!string.IsNullOrEmpty(projection)){using var srs = new SpatialReference(projection);Console.WriteLine($"坐标系: {srs.GetName()}");}// 波段信息for (int i = 1; i <= ds.RasterCount; i++){using var band = ds.GetRasterBand(i);Console.WriteLine($"\n波段 {i}:");Console.WriteLine($" 数据类型: {Gdal.GetDataTypeName(band.DataType)}");double nodata;int hasNodata;band.GetNoDataValue(out nodata, out hasNodata);if (hasNodata != 0){Console.WriteLine($" 无效值: {nodata}");}double min, max, mean, stddev;band.GetStatistics(0, 1, out min, out max, out mean, out stddev);Console.WriteLine($" 统计: min={min:F2}, max={max:F2}, mean={mean:F2}, std={stddev:F2}");}}/// <summary>/// 读取波段数据为数组/// </summary>public static double[,] ReadBandAsArray(string filepath, int bandIndex = 1){GdalInitializer.Initialize();using var ds = Gdal.Open(filepath, Access.GA_ReadOnly);if (ds == null){throw new Exception($"无法打开文件: {filepath}");}int width = ds.RasterXSize;int height = ds.RasterYSize;using var band = ds.GetRasterBand(bandIndex);// 读取为一维数组double[] data = new double[width * height];band.ReadRaster(0, 0, width, height, data, width, height, 0, 0);// 转换为二维数组double[,] result = new double[height, width];for (int y = 0; y < height; y++){for (int x = 0; x < width; x++){result[y, x] = data[y * width + x];}}return result;}/// <summary>/// 分块读取栅格数据/// </summary>public static void ReadInBlocks(string filepath, Action<int, int, int, int, double[]> processor){GdalInitializer.Initialize();using var ds = Gdal.Open(filepath, Access.GA_ReadOnly);if (ds == null){throw new Exception($"无法打开文件: {filepath}");}int width = ds.RasterXSize;int height = ds.RasterYSize;using var band = ds.GetRasterBand(1);int blockWidth, blockHeight;band.GetBlockSize(out blockWidth, out blockHeight);Console.WriteLine($"块大小: {blockWidth} x {blockHeight}");for (int y = 0; y < height; y += blockHeight){for (int x = 0; x < width; x += blockWidth){int actualWidth = Math.Min(blockWidth, width - x);int actualHeight = Math.Min(blockHeight, height - y);double[] data = new double[actualWidth * actualHeight];band.ReadRaster(x, y, actualWidth, actualHeight, data, actualWidth, actualHeight, 0, 0);processor(x, y, actualWidth, actualHeight, data);}}}
}
9.3.2 创建栅格数据
using OSGeo.GDAL;
using OSGeo.OSR;namespace GdalDemo.Raster;/// <summary>
/// 栅格数据写入器
/// </summary>
public class RasterWriter
{/// <summary>/// 创建 GeoTIFF 文件/// </summary>public static void CreateGeoTiff(string filepath,int width,int height,int bands,DataType dataType,double[] geoTransform,int epsg,double[,]? data = null){GdalInitializer.Initialize();using var driver = Gdal.GetDriverByName("GTiff");if (driver == null){throw new Exception("GTiff 驱动不可用");}// 创建选项string[] options = new string[]{"COMPRESS=LZW","TILED=YES","BLOCKXSIZE=256","BLOCKYSIZE=256"};using var ds = driver.Create(filepath, width, height, bands, dataType, options);if (ds == null){throw new Exception($"无法创建文件: {filepath}");}// 设置地理变换if (geoTransform != null){ds.SetGeoTransform(geoTransform);}// 设置投影if (epsg > 0){using var srs = new SpatialReference("");srs.ImportFromEPSG(epsg);ds.SetProjection(srs.ExportToWkt());}// 写入数据if (data != null){using var band = ds.GetRasterBand(1);// 转换为一维数组double[] flatData = new double[width * height];for (int y = 0; y < height; y++){for (int x = 0; x < width; x++){flatData[y * width + x] = data[y, x];}}band.WriteRaster(0, 0, width, height, flatData, width, height, 0, 0);band.SetNoDataValue(-9999);band.ComputeStatistics(false, out _, out _, out _, out _, null, null);}ds.FlushCache();Console.WriteLine($"创建完成: {filepath}");}/// <summary>/// 创建示例 DEM/// </summary>public static void CreateSampleDEM(string filepath){int width = 1000;int height = 1000;// 生成模拟高程数据double[,] data = new double[height, width];Random rand = new Random();for (int y = 0; y < height; y++){for (int x = 0; x < width; x++){data[y, x] = 100 +50 * Math.Sin(x * Math.PI / 100) * Math.Cos(y * Math.PI / 100) +rand.NextDouble() * 10;}}// 地理变换double[] geoTransform = new double[]{116.0, // 原点X0.001, // 像素宽度0, // 旋转40.0, // 原点Y0, // 旋转-0.001 // 像素高度};CreateGeoTiff(filepath, width, height, 1, DataType.GDT_Float32,geoTransform, 4326, data);}/// <summary>/// 创建 RGB 彩色影像/// </summary>public static void CreateRGBImage(string filepath,int width,int height,byte[,] red,byte[,] green,byte[,] blue,double[] geoTransform,int epsg){GdalInitializer.Initialize();using var driver = Gdal.GetDriverByName("GTiff");string[] options = new string[]{"COMPRESS=LZW","PHOTOMETRIC=RGB"};using var ds = driver.Create(filepath, width, height, 3, DataType.GDT_Byte, options);if (geoTransform != null){ds.SetGeoTransform(geoTransform);}if (epsg > 0){using var srs = new SpatialReference("");srs.ImportFromEPSG(epsg);ds.SetProjection(srs.ExportToWkt());}// 写入各波段byte[][] bandData = new byte[][] {FlattenArray(red),FlattenArray(green),FlattenArray(blue)};ColorInterp[] colorInterps = new ColorInterp[]{ColorInterp.GCI_RedBand,ColorInterp.GCI_GreenBand,ColorInterp.GCI_BlueBand};for (int i = 0; i < 3; i++){using var band = ds.GetRasterBand(i + 1);band.WriteRaster(0, 0, width, height, bandData[i], width, height, 0, 0);band.SetColorInterpretation(colorInterps[i]);}ds.FlushCache();}private static byte[] FlattenArray(byte[,] array){int height = array.GetLength(0);int width = array.GetLength(1);byte[] result = new byte[width * height];for (int y = 0; y < height; y++){for (int x = 0; x < width; x++){result[y * width + x] = array[y, x];}}return result;}
}
9.3.3 栅格处理操作
using OSGeo.GDAL;namespace GdalDemo.Raster;/// <summary>
/// 栅格处理操作
/// </summary>
public class RasterProcessor
{/// <summary>/// 重投影栅格/// </summary>public static void Reproject(string srcPath, string dstPath, string dstSRS){GdalInitializer.Initialize();using var srcDs = Gdal.Open(srcPath, Access.GA_ReadOnly);if (srcDs == null){throw new Exception($"无法打开文件: {srcPath}");}var options = new GDALWarpAppOptions(new string[]{"-t_srs", dstSRS,"-r", "bilinear","-co", "COMPRESS=LZW","-co", "TILED=YES"});using var dstDs = Gdal.Warp(dstPath, new Dataset[] { srcDs }, options, null, null);Console.WriteLine($"重投影完成: {dstPath}");}/// <summary>/// 裁剪栅格/// </summary>public static void Clip(string srcPath, string dstPath,double minX, double minY, double maxX, double maxY){GdalInitializer.Initialize();using var srcDs = Gdal.Open(srcPath, Access.GA_ReadOnly);var options = new GDALTranslateOptions(new string[]{"-projwin", minX.ToString(), maxY.ToString(), maxX.ToString(), minY.ToString(),"-co", "COMPRESS=LZW"});using var dstDs = Gdal.Translate(dstPath, srcDs, options, null, null);Console.WriteLine($"裁剪完成: {dstPath}");}/// <summary>/// 使用矢量边界裁剪/// </summary>public static void ClipByVector(string srcPath, string dstPath, string cutlinePath){GdalInitializer.Initialize();using var srcDs = Gdal.Open(srcPath, Access.GA_ReadOnly);var options = new GDALWarpAppOptions(new string[]{"-cutline", cutlinePath,"-crop_to_cutline","-dstnodata", "-9999","-co", "COMPRESS=LZW"});using var dstDs = Gdal.Warp(dstPath, new Dataset[] { srcDs }, options, null, null);Console.WriteLine($"裁剪完成: {dstPath}");}/// <summary>/// 镶嵌多个栅格/// </summary>public static void Mosaic(string[] srcPaths, string dstPath){GdalInitializer.Initialize();// 打开所有源数据集Dataset[] srcDatasets = new Dataset[srcPaths.Length];for (int i = 0; i < srcPaths.Length; i++){srcDatasets[i] = Gdal.Open(srcPaths[i], Access.GA_ReadOnly);if (srcDatasets[i] == null){throw new Exception($"无法打开文件: {srcPaths[i]}");}}try{// 创建 VRTvar vrtOptions = new GDALBuildVRTOptions(Array.Empty<string>());using var vrtDs = Gdal.BuildVRT("", srcDatasets, vrtOptions, null, null);// 转换为 GeoTIFFvar translateOptions = new GDALTranslateOptions(new string[]{"-co", "COMPRESS=LZW","-co", "TILED=YES","-co", "BIGTIFF=IF_SAFER"});using var dstDs = Gdal.Translate(dstPath, vrtDs, translateOptions, null, null);Console.WriteLine($"镶嵌完成: {dstPath}");}finally{foreach (var ds in srcDatasets){ds?.Dispose();}}}/// <summary>/// 格式转换/// </summary>public static void Convert(string srcPath, string dstPath, string format){GdalInitializer.Initialize();using var srcDs = Gdal.Open(srcPath, Access.GA_ReadOnly);var options = new GDALTranslateOptions(new string[]{"-of", format});using var dstDs = Gdal.Translate(dstPath, srcDs, options, null, null);Console.WriteLine($"转换完成: {dstPath}");}/// <summary>/// 创建金字塔/// </summary>public static void BuildOverviews(string filepath, int[] levels){GdalInitializer.Initialize();using var ds = Gdal.Open(filepath, Access.GA_Update);if (ds == null){throw new Exception($"无法打开文件: {filepath}");}if (levels == null || levels.Length == 0){levels = new int[] { 2, 4, 8, 16, 32 };}ds.BuildOverviews("AVERAGE", levels, null, null);Console.WriteLine($"金字塔创建完成: {filepath}");}
}
9.4 矢量数据处理
9.4.1 读取矢量数据
using OSGeo.OGR;
using OSGeo.OSR;namespace GdalDemo.Vector;/// <summary>
/// 矢量数据读取器
/// </summary>
public class VectorReader
{/// <summary>/// 读取矢量数据信息/// </summary>public static void ReadVectorInfo(string filepath){GdalInitializer.Initialize();using var ds = Ogr.Open(filepath, 0);if (ds == null){Console.WriteLine($"无法打开文件: {filepath}");return;}Console.WriteLine($"数据源: {ds.GetDescription()}");Console.WriteLine($"图层数: {ds.GetLayerCount()}");for (int i = 0; i < ds.GetLayerCount(); i++){using var layer = ds.GetLayerByIndex(i);Console.WriteLine($"\n图层 {i}: {layer.GetName()}");Console.WriteLine($" 要素数: {layer.GetFeatureCount(1)}");Console.WriteLine($" 几何类型: {Ogr.GeometryTypeToName(layer.GetGeomType())}");// 范围Envelope extent = new Envelope();layer.GetExtent(extent, 1);Console.WriteLine($" 范围: ({extent.MinX:F4}, {extent.MinY:F4}) - ({extent.MaxX:F4}, {extent.MaxY:F4})");// 空间参考using var srs = layer.GetSpatialRef();if (srs != null){Console.WriteLine($" 坐标系: {srs.GetName()}");}// 字段定义using var layerDefn = layer.GetLayerDefn();Console.WriteLine($" 字段数: {layerDefn.GetFieldCount()}");for (int j = 0; j < layerDefn.GetFieldCount(); j++){using var fieldDefn = layerDefn.GetFieldDefn(j);Console.WriteLine($" - {fieldDefn.GetName()}: {fieldDefn.GetTypeName()}({fieldDefn.GetWidth()})");}}}/// <summary>/// 遍历要素/// </summary>public static void IterateFeatures(string filepath, Action<Feature>? processor = null){GdalInitializer.Initialize();using var ds = Ogr.Open(filepath, 0);if (ds == null){throw new Exception($"无法打开文件: {filepath}");}using var layer = ds.GetLayerByIndex(0);layer.ResetReading();Feature? feature;while ((feature = layer.GetNextFeature()) != null){using (feature){if (processor != null){processor(feature);}else{Console.WriteLine($"FID: {feature.GetFID()}");using var geom = feature.GetGeometryRef();if (geom != null){Console.WriteLine($" 几何类型: {geom.GetGeometryName()}");Console.WriteLine($" WKT: {geom.ExportToWkt().Substring(0, Math.Min(50, geom.ExportToWkt().Length))}...");}}}}}/// <summary>/// 读取要素为字典列表/// </summary>public static List<Dictionary<string, object?>> ReadFeatures(string filepath,string? whereClause = null,(double MinX, double MinY, double MaxX, double MaxY)? bbox = null){GdalInitializer.Initialize();using var ds = Ogr.Open(filepath, 0);if (ds == null){throw new Exception($"无法打开文件: {filepath}");}using var layer = ds.GetLayerByIndex(0);// 设置过滤器if (!string.IsNullOrEmpty(whereClause)){layer.SetAttributeFilter(whereClause);}if (bbox.HasValue){layer.SetSpatialFilterRect(bbox.Value.MinX, bbox.Value.MinY,bbox.Value.MaxX, bbox.Value.MaxY);}var features = new List<Dictionary<string, object?>>();using var layerDefn = layer.GetLayerDefn();Feature? feature;layer.ResetReading();while ((feature = layer.GetNextFeature()) != null){using (feature){var dict = new Dictionary<string, object?>{["fid"] = feature.GetFID()};using var geom = feature.GetGeometryRef();if (geom != null){dict["geometry"] = geom.ExportToWkt();}for (int i = 0; i < layerDefn.GetFieldCount(); i++){using var fieldDefn = layerDefn.GetFieldDefn(i);string fieldName = fieldDefn.GetName();if (feature.IsFieldNull(i)){dict[fieldName] = null;}else{dict[fieldName] = fieldDefn.GetFieldType() switch{FieldType.OFTInteger => feature.GetFieldAsInteger(i),FieldType.OFTInteger64 => feature.GetFieldAsInteger64(i),FieldType.OFTReal => feature.GetFieldAsDouble(i),_ => feature.GetFieldAsString(i)};}}features.Add(dict);}}return features;}
}
9.4.2 创建矢量数据
using OSGeo.OGR;
using OSGeo.OSR;namespace GdalDemo.Vector;/// <summary>
/// 矢量数据写入器
/// </summary>
public class VectorWriter
{/// <summary>/// 创建 Shapefile/// </summary>public static void CreateShapefile(string filepath,wkbGeometryType geomType,int epsg,List<(string Name, FieldType Type, int Width)> fields,List<Dictionary<string, object?>> features){GdalInitializer.Initialize();using var driver = Ogr.GetDriverByName("ESRI Shapefile");if (driver == null){throw new Exception("Shapefile 驱动不可用");}// 删除已存在的文件if (File.Exists(filepath)){driver.DeleteDataSource(filepath);}using var ds = driver.CreateDataSource(filepath, Array.Empty<string>());if (ds == null){throw new Exception($"无法创建数据源: {filepath}");}// 创建空间参考using var srs = new SpatialReference("");srs.ImportFromEPSG(epsg);// 创建图层using var layer = ds.CreateLayer("layer", srs, geomType, Array.Empty<string>());// 创建字段foreach (var (name, type, width) in fields){using var fieldDefn = new FieldDefn(name, type);if (width > 0){fieldDefn.SetWidth(width);}layer.CreateField(fieldDefn, 1);}// 获取图层定义using var layerDefn = layer.GetLayerDefn();// 添加要素foreach (var featureData in features){using var feature = new Feature(layerDefn);// 设置几何if (featureData.TryGetValue("geometry", out var geomObj) && geomObj is string wkt){using var geom = Geometry.CreateFromWkt(wkt);feature.SetGeometry(geom);}// 设置属性foreach (var (name, _, _) in fields){if (featureData.TryGetValue(name, out var value) && value != null){int fieldIndex = feature.GetFieldIndex(name);if (fieldIndex >= 0){switch (value){case int intVal:feature.SetField(fieldIndex, intVal);break;case long longVal:feature.SetField(fieldIndex, longVal);break;case double doubleVal:feature.SetField(fieldIndex, doubleVal);break;default:feature.SetField(fieldIndex, value.ToString());break;}}}}layer.CreateFeature(feature);}Console.WriteLine($"创建完成: {filepath}");}/// <summary>/// 创建 GeoJSON/// </summary>public static void CreateGeoJSON(string filepath,wkbGeometryType geomType,int epsg,List<(string Name, FieldType Type, int Width)> fields,List<Dictionary<string, object?>> features){GdalInitializer.Initialize();using var driver = Ogr.GetDriverByName("GeoJSON");if (driver == null){throw new Exception("GeoJSON 驱动不可用");}using var ds = driver.CreateDataSource(filepath, Array.Empty<string>());using var srs = new SpatialReference("");srs.ImportFromEPSG(epsg);using var layer = ds.CreateLayer("features", srs, geomType, Array.Empty<string>());foreach (var (name, type, width) in fields){using var fieldDefn = new FieldDefn(name, type);if (width > 0){fieldDefn.SetWidth(width);}layer.CreateField(fieldDefn, 1);}using var layerDefn = layer.GetLayerDefn();foreach (var featureData in features){using var feature = new Feature(layerDefn);if (featureData.TryGetValue("geometry", out var geomObj) && geomObj is string wkt){using var geom = Geometry.CreateFromWkt(wkt);feature.SetGeometry(geom);}foreach (var (name, _, _) in fields){if (featureData.TryGetValue(name, out var value) && value != null){int fieldIndex = feature.GetFieldIndex(name);if (fieldIndex >= 0){feature.SetField(fieldIndex, value.ToString());}}}layer.CreateFeature(feature);}Console.WriteLine($"创建完成: {filepath}");}/// <summary>/// 创建示例点数据/// </summary>public static void CreateSamplePoints(string filepath){var fields = new List<(string Name, FieldType Type, int Width)>{("name", FieldType.OFTString, 50),("population", FieldType.OFTInteger64, 0)};var features = new List<Dictionary<string, object?>>{new() { ["geometry"] = "POINT(116.4 39.9)", ["name"] = "北京", ["population"] = 21540000L },new() { ["geometry"] = "POINT(121.5 31.2)", ["name"] = "上海", ["population"] = 24280000L },new() { ["geometry"] = "POINT(113.3 23.1)", ["name"] = "广州", ["population"] = 18680000L }};CreateShapefile(filepath, wkbGeometryType.wkbPoint, 4326, fields, features);}
}
9.5 坐标转换
using OSGeo.OGR;
using OSGeo.OSR;namespace GdalDemo.Coordinate;/// <summary>
/// 坐标转换工具
/// </summary>
public class CoordinateTransformer
{/// <summary>/// 转换坐标点/// </summary>public static (double X, double Y) TransformPoint(double x, double y,int srcEPSG, int dstEPSG){GdalInitializer.Initialize();using var srcSRS = new SpatialReference("");srcSRS.ImportFromEPSG(srcEPSG);using var dstSRS = new SpatialReference("");dstSRS.ImportFromEPSG(dstEPSG);using var transform = new CoordinateTransformation(srcSRS, dstSRS);double[] point = new double[] { x, y, 0 };transform.TransformPoint(point);return (point[0], point[1]);}/// <summary>/// 批量转换坐标/// </summary>public static List<(double X, double Y)> TransformPoints(List<(double X, double Y)> points,int srcEPSG, int dstEPSG){GdalInitializer.Initialize();using var srcSRS = new SpatialReference("");srcSRS.ImportFromEPSG(srcEPSG);using var dstSRS = new SpatialReference("");dstSRS.ImportFromEPSG(dstEPSG);using var transform = new CoordinateTransformation(srcSRS, dstSRS);var results = new List<(double X, double Y)>();foreach (var (x, y) in points){double[] point = new double[] { x, y, 0 };transform.TransformPoint(point);results.Add((point[0], point[1]));}return results;}/// <summary>/// 转换几何对象/// </summary>public static Geometry TransformGeometry(Geometry geom,int srcEPSG, int dstEPSG){GdalInitializer.Initialize();using var srcSRS = new SpatialReference("");srcSRS.ImportFromEPSG(srcEPSG);using var dstSRS = new SpatialReference("");dstSRS.ImportFromEPSG(dstEPSG);using var transform = new CoordinateTransformation(srcSRS, dstSRS);var newGeom = geom.Clone();newGeom.Transform(transform);return newGeom;}
}
9.6 实用工具类
using OSGeo.GDAL;
using OSGeo.OGR;namespace GdalDemo.Utils;/// <summary>
/// GDAL 资源包装器
/// </summary>
public class GdalResource : IDisposable
{private Dataset? _rasterDs;private DataSource? _vectorDs;private bool _disposed = false;public Dataset? RasterDataset => _rasterDs;public DataSource? VectorDataSource => _vectorDs;private GdalResource() { }public static GdalResource OpenRaster(string filepath, Access access = Access.GA_ReadOnly){GdalInitializer.Initialize();var resource = new GdalResource();resource._rasterDs = Gdal.Open(filepath, access);if (resource._rasterDs == null){throw new Exception($"无法打开栅格文件: {filepath}");}return resource;}public static GdalResource OpenVector(string filepath, int update = 0){GdalInitializer.Initialize();var resource = new GdalResource();resource._vectorDs = Ogr.Open(filepath, update);if (resource._vectorDs == null){throw new Exception($"无法打开矢量文件: {filepath}");}return resource;}public void Dispose(){Dispose(true);GC.SuppressFinalize(this);}protected virtual void Dispose(bool disposing){if (!_disposed){if (disposing){_rasterDs?.Dispose();_vectorDs?.Dispose();}_rasterDs = null;_vectorDs = null;_disposed = true;}}~GdalResource(){Dispose(false);}
}
9.7 主程序示例
using GdalDemo;
using GdalDemo.Raster;
using GdalDemo.Vector;
using GdalDemo.Coordinate;// 初始化 GDAL
GdalInitializer.Initialize();Console.WriteLine("=== GDAL .NET 示例 ===\n");// 1. 创建示例 DEM
Console.WriteLine("1. 创建示例 DEM...");
RasterWriter.CreateSampleDEM("sample_dem.tif");// 2. 读取栅格信息
Console.WriteLine("\n2. 读取栅格信息...");
RasterReader.ReadRasterInfo("sample_dem.tif");// 3. 创建示例点数据
Console.WriteLine("\n3. 创建示例点数据...");
VectorWriter.CreateSamplePoints("cities.shp");// 4. 读取矢量信息
Console.WriteLine("\n4. 读取矢量信息...");
VectorReader.ReadVectorInfo("cities.shp");// 5. 坐标转换
Console.WriteLine("\n5. 坐标转换...");
var (x, y) = CoordinateTransformer.TransformPoint(116.4, 39.9, 4326, 3857);
Console.WriteLine($"WGS84 (116.4, 39.9) -> Web Mercator ({x:F2}, {y:F2})");Console.WriteLine("\n=== 完成 ===");
9.8 本章小结
本章介绍了 C#/.NET GDAL 开发：
- 环境配置：使用 MaxRev.Gdal.Universal NuGet 包
- 栅格处理：读取、创建和处理栅格数据
- 矢量处理：读取、创建和查询矢量数据
- 坐标转换：使用 OSR 进行坐标转换
- 最佳实践：资源管理和 IDisposable 模式
9.9 思考与练习
- 比较 MaxRev.Gdal.Universal 和其他 GDAL NuGet 包的优缺点。
- 如何在 ASP.NET Core Web API 中使用 GDAL？
- 实现一个支持异步操作的栅格处理类。
- 编写一个批量格式转换工具。
- 如何处理 GDAL 中的大文件和内存管理？