【Demo 0014】图形对象--路径

路径可能大家在实际工作中接触的不多，它与系统默认的图形对象(pen, brush, font)不同， 它被创建后会直接选入到DC中，选入之后我们可以其描边，填充以及同时描边和填充还支持将捕捉图形的路径，并可以将路径直接转换成区域等;  我们在实现镂空字时会用到，带有背景字体的地方也会用到， 就以上所有的相对常用的方法进行展开学习.

一、API 学习

     1.  创建路径

   BOOL BeginPath(HDC hDC)

          BOOL EndPath(HDC hDC)

          这两个函数成对使用，用于获取GDI函数绘制的图形路径(轨迹)并在此区间的绘图函数不会显示到DC中

     2.  路径描边和填充

          BOOL StrokePath(HDC hDC) 

          功能: 使用当前DC中画笔对路径进行描边

         BOOL FillPath(HDC hDC)

          功能: 使用当前DC中画刷对路径填充

          BOOL StrokeAndFillPath(HDC hDC)

          功能: 使用当前DC中画笔和画刷对路径进行描边并填充

          BOOL WidenPath(HDC hDC)

          功能:  将当前路径加宽

     3.  路径轨迹捕捉

          BOOL FlattenPath(HDC hDC)

          功能: 将所有的曲线转成短段

          int GetPath(HDC hDC, LPPOINT lpPoints, LPBYTE lpTypes, int nSize)

           功能: 获取路径中短段的起点和终点，使用此函数前要点调用FlattenPath函数(将轨迹变成条线段)

     4.  路径转成区域

          HRGN PathToRegion(HDC hDC)

          功能:  将当前DC中的路径转成区域

二、演示代码分析

     将客户区划分为６个区域，每个区域演示不同的内容

a.  路径填充

      b.  路径描边

      c.  路径描边和填充

      d.  加宽路径并描边

      e.  获取路径关键点并显示

f.  将路径转成区域并用背影填充区域

     

void CDemoWnd :: _DemoFillPath ( HDC hDC , RECT rtArea )
{    
     int nSaveDC = SaveDC ( hDC );
     _DrawPath ( hDC , rtArea );

     FillPath ( hDC );
     FlattenPath ( hDC );

     RestoreDC ( hDC , nSaveDC );

     return ;
}
void CDemoWnd :: _DemoStrokPath ( HDC hDC , RECT rtArea )
{
     int nSaveDC = SaveDC ( hDC );
     _DrawPath ( hDC , rtArea );

     StrokePath ( hDC );

     RestoreDC ( hDC , nSaveDC );
     return ;
}

void CDemoWnd :: _DemoStrokAndFillPath ( HDC hDC , RECT rtArea )
{
     int nSaveDC = SaveDC ( hDC );
     _DrawPath ( hDC , rtArea );

     StrokeAndFillPath ( hDC );

     RestoreDC ( hDC , nSaveDC );
     return ;
}

void CDemoWnd :: _DemoWidenPath ( HDC hDC , RECT rtArea )
{
     int nSaveDC = SaveDC ( hDC );
     _DrawPath ( hDC , rtArea );

     WidenPath ( hDC );
     StrokePath ( hDC );

     RestoreDC ( hDC , nSaveDC );

     return ;
}

void CDemoWnd :: _DemoPathToRegion ( HDC hDC , RECT rtArea )
{
     int nSaveDC = SaveDC ( hDC );
     _DrawPath ( hDC , rtArea );

     HRGN hRgn = PathToRegion ( hDC );
     HBITMAP hBitmap = LoadBitmap ( GetModuleHandle ( NULL ), MAKEINTRESOURCE ( IDB_BACKGROUND ));
     HBRUSH hBrush = CreatePatternBrush ( hBitmap );
     FillRgn ( hDC , hRgn , hBrush );
     DeleteObject ( hBrush );
     DeleteObject ( hRgn );

     RestoreDC ( hDC , nSaveDC );

     return ;
}

void CDemoWnd :: _DemoGetPath ( HDC hDC , RECT rtArea )
{
     int nSaveDC = SaveDC ( hDC );
     _DrawPath ( hDC , rtArea );

     FlattenPath ( hDC );
     int nPtCount = GetPath ( hDC , NULL , NULL , 0);
     assert ( nPtCount > 0);
     POINT * ptKeyPoints = new POINT [ nPtCount ];
     BYTE * byInfo = new BYTE [ nPtCount ];
     int nCount = GetPath ( hDC , ptKeyPoints , byInfo , nPtCount );

     for ( int ii = 0; ii < nPtCount ; ii ++)
    {
         Rectangle ( hDC , ptKeyPoints [ ii ]. x - 1, ptKeyPoints [ ii ]. y - 1, ptKeyPoints [ ii ]. x + 1, ptKeyPoints [ ii ]. y + 1);
    }
     FillPath ( hDC );
     delete [] byInfo ;
     delete [] ptKeyPoints ;

     RestoreDC ( hDC , nSaveDC );

     return ;
}

void CDemoWnd :: _DrawPath ( HDC hDC , RECT rtArea )
{
     const TCHAR * szText = _T ( "Hello, Öйú" );
     //--: Font Info
     LOGFONT LogFont ;
     GetObject ( GetCurrentObject ( hDC , OBJ_FONT ), sizeof ( LOGFONT ), & LogFont );
     _tcscpy ( LogFont . lfFaceName , _T ( "΢ÈíÑźÚ" ));
     LogFont . lfQuality     = CLEARTYPE_QUALITY ;
     LogFont . lfHeight     = 100;
     LogFont . lfWidth         = 50;
     HFONT hFont = CreateFontIndirect (& LogFont );
     SelectObject ( hDC , hFont );
     SetBkMode ( hDC , TRANSPARENT );

     //--: Brush Info
     SelectObject ( hDC , GetStockObject ( DC_BRUSH ));
     SetDCBrushColor ( hDC , RGB (255, 255, 128));
    
     //--: Pen Info
     SelectObject ( hDC , GetStockPen ( DC_PEN ));
     SetDCPenColor ( hDC , RGB (128, 128, 255));

     RECT rtTmp = rtArea ;
     InflateRect (& rtTmp , -10, -10);
     rtTmp . right = rtTmp . left + 50 + rtTmp . bottom - rtTmp . top ;

     POINT ptVertex [] = { { rtTmp . left , rtTmp . bottom} ,
                         { rtTmp . left + ( rtTmp . right - rtTmp . left ) / 2, rtTmp . top} ,
                         { rtTmp . right , rtTmp . bottom}
    } ;

     BeginPath ( hDC );
     DrawText ( hDC , szText , _tcslen ( szText ), & rtArea , DT_SINGLELINE | DT_VCENTER | DT_CENTER );
     Polygon ( hDC , ptVertex , sizeof ( ptVertex ) / sizeof (* ptVertex ));
     EndPath ( hDC );
     SelectObject ( hDC , GetStockObject ( SYSTEM_FONT ));
     DeleteObject ( hFont );
}

 

演示代码