【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