GDAL/OGR 地理要素样式管理器（一）

       很多人对GDAL/OGR已经很熟悉了，GDAL/OGR具有对许多栅格和矢量数据的读写功能，而我接触GDAL已经有1年的时间了，但是对于OGR中如何获得点线面要素的颜色，线宽，线型信息很是陌生。相信很多人也不是太清楚吧。下面代码可以获取字段和坐标信息：

#include "ogrsf_frmts.h"
#include <iostream>
#include <string>
using namespace std;
int main()
{
	OGRRegisterAll();
	// 对中文路径的支持
	CPLSetConfigOption("GDAL_FILENAME_IS_UTF8", "NO");
	OGRDataSource *poDataSource = OGRSFDriverRegistrar::Open(
		"G:/5.dxf",TRUE);
	if( poDataSource == NULL )
	{
		cout << "文件打开失败" << endl;
		system("pause");
		return 0;
	}
	OGRLayer *poLayer = poDataSource->GetLayer(0);
	OGRFeature *poFeature;
	while( (poFeature = poLayer->GetNextFeature()) != NULL )
	{
		OGRFeatureDefn *poFDefn = poLayer->GetLayerDefn();
		int iField;

		for( iField = 0; iField < poFDefn->GetFieldCount(); iField++ )
		{
			OGRFieldDefn *poFieldDefn = poFDefn->GetFieldDefn( iField );

			if( poFieldDefn->GetType() == OFTInteger )
				printf( "%d,", poFeature->GetFieldAsInteger( iField ) );
			else if( poFieldDefn->GetType() == OFTReal )
				printf( "%.3f,", poFeature->GetFieldAsDouble(iField) );
			else if( poFieldDefn->GetType() == OFTString )
				printf( "%s,", poFeature->GetFieldAsString(iField) );
			else
				printf( "%s,", poFeature->GetFieldAsString(iField) );
		}
		
		printf( "\n");

		OGRGeometry *poGeometry;

		poGeometry = poFeature->GetGeometryRef();
		if( poGeometry != NULL 
			&& wkbFlatten(poGeometry->getGeometryType()) == wkbLineString )
		{
			OGRLineString *ogrLineString = (OGRLineString *)poGeometry;
			
			// 得到线串点的数目
			int nPointNum = ogrLineString->getNumPoints();

			// 线要素的点坐标
			for (int i = 0; i < nPointNum; i++ )
			{
				OGRPoint poPoint;
				ogrLineString->getPoint(i,&poPoint);

				printf( "%.3f,%3.f\n", poPoint.getX(), poPoint.getY() );
			}
		}
		else
		{
			printf( "no line geometry\n" );
		}
		OGRFeature::DestroyFeature(poFeature);
	}
	OGRDataSource::DestroyDataSource( poDataSource );
	system("pause");
	return 1;
}

运行结果:

看上面代码，我认为颜色信息应该也在OGRFeature类中，查看源码，发现OGRFeature中有：

两个有关样式的成员：

char *              m_pszStyleString;

OGRStyleTable       *m_poStyleTable;

六个有关样式接口函数：

virtual const char *GetStyleString();

    virtual void        SetStyleString( const char * );

    virtual void        SetStyleStringDirectly( char * );

    virtual OGRStyleTable *GetStyleTable() { return m_poStyleTable; }

    virtual void        SetStyleTable(OGRStyleTable *poStyleTable);

    virtual void        SetStyleTableDirectly(OGRStyleTable *poStyleTable)

                            { if ( m_poStyleTable ) delete m_poStyleTable;

                              m_poStyleTable = poStyleTable; }

于是，下一步，在源码中去找到OGRStyleTable的定义。

发现OGRStyleTable定义在ogrfeaturestyle.h头文件中。

在ogrfeaturestyle.h中有7个类：

OGRStyleTable ：样式表类

OGRStyleMgr：样式管理器类

OGRStyleTool：样式工具类

继承于OGRStyleTool的四个类：

OGRStylePen：样式画笔类

OGRStyleBrush：样式画刷类

OGRStyleSymbol：样式符号类

OGRStyleLabel：样式标签类

下面我们获取线要素画笔颜色：

int main()
{
	OGRRegisterAll();
	// 对中文路径的支持
	CPLSetConfigOption("GDAL_FILENAME_IS_UTF8", "NO");
	OGRDataSource *poDataSource = OGRSFDriverRegistrar::Open(
		"G:/5.dxf",TRUE);
	if( poDataSource == NULL )
	{
		cout << "文件打开失败" << endl;
		system("pause");
		return 0;
	}
	OGRLayer *poLayer = poDataSource->GetLayer(0);
	OGRFeature *poFeature;
	while( (poFeature = poLayer->GetNextFeature()) != NULL )
	{
		OGRFeatureDefn *poFDefn = poLayer->GetLayerDefn();
		int iField;

		for( iField = 0; iField < poFDefn->GetFieldCount(); iField++ )
		{
			OGRFieldDefn *poFieldDefn = poFDefn->GetFieldDefn( iField );

			if( poFieldDefn->GetType() == OFTInteger )
				printf( "%d,", poFeature->GetFieldAsInteger( iField ) );
			else if( poFieldDefn->GetType() == OFTReal )
				printf( "%.3f,", poFeature->GetFieldAsDouble(iField) );
			else if( poFieldDefn->GetType() == OFTString )
				printf( "%s,", poFeature->GetFieldAsString(iField) );
			else
				printf( "%s,", poFeature->GetFieldAsString(iField) );
		}
		
		printf( "\n");

		OGRGeometry *poGeometry;

		poGeometry = poFeature->GetGeometryRef();
		if( poGeometry != NULL 
			&& wkbFlatten(poGeometry->getGeometryType()) == wkbLineString )
		{
			OGRLineString *ogrLineString = (OGRLineString *)poGeometry;
			/*****************************获取画笔颜色*******************************/
			// 样式管理器
			OGRStyleMgr oStyleMgr;
			// 初始化样式管理器
			oStyleMgr.InitStyleString(poFeature->GetStyleString());
			// 样式工具的个数
			int styleToolCount = oStyleMgr.GetPartCount();
			for(int i = 0;i < styleToolCount; i++)
			{
				OGRStyleTool *pStyleTool = oStyleMgr.GetPart(i);
				switch(pStyleTool->GetType())
				{
				case OGRSTCNone:
					{
						break;
					}
				case OGRSTCPen:
					{
						OGRStylePen *pStylePen = (OGRStylePen *)pStyleTool;
						GBool gbool;
						const char *pzsClr = pStylePen->Color(gbool);
						int r,g,b,t;// 红、绿、蓝、通明度
						pStylePen->GetRGBFromString(pzsClr,r,g,b,t);
						if(!gbool) // 如果颜色不为空
						{
							printf( "线颜色：R = %d,G = %d,B = %d\n", r,g,b );
						}
						break;
					}
				case OGRSTCBrush:
					{
						break;
					}
				case OGRSTCSymbol:
					{
						break;
					}
				case OGRSTCLabel:
					{
						break;
					}
				case OGRSTCVector:
					{
						break;
					}
				}

				if(pStyleTool)
					delete pStyleTool;
			}
			/************************************************************************/
			// 得到线串点的数目
			int nPointNum = ogrLineString->getNumPoints();

			// 线要素的点坐标
			for (int i = 0; i < nPointNum; i++ )
			{
				OGRPoint poPoint;
				ogrLineString->getPoint(i,&poPoint);

				printf( "%.3f,%3.f\n", poPoint.getX(), poPoint.getY() );
			}
		}
		else
		{
			printf( "no line geometry\n" );
		}
		OGRFeature::DestroyFeature(poFeature);
	}
	OGRDataSource::DestroyDataSource( poDataSource );
	system("pause");
	return 1;
}

运行结果：