【Demo 0008】绘图对象

【Demo 0008】绘图对象–画刷

前文中我们讲述了GDI绘图对象之一画笔，今天继续学习绘图对象之二画刷，画刷通常用于将特定的颜色或图案填充到封闭式区域的图形中，封闭式图形有矩形，圆形，多边形, 路径等; 它和画笔一样也具备自身的属性: 样式(风格，图案)和行为.

一、创建画刷

GDI 提供四种方法创建画刷:

1. HBRUSH CreateSolidBrush(COLORREF crColor)

crColor -- 画刷的颜色

创建特定颜色实心风格的画刷

void CDemoWnd::DemoSolidBrush(HDC hDC, RECT& rtGrid)
 {
     InflateRect(&rtGrid, -5, -5);
 
     int nSavedDC = SaveDC(hDC);
 
     HBRUSH hBrush     = CreateSolidBrush(RGB(255, 128, 128));
     HBRUSH hOldBrush = (HBRUSH)SelectObject(hDC, hBrush);
     
     SetBkMode(hDC, TRANSPARENT);
     Rectangle(hDC, rtGrid.left, rtGrid.top, rtGrid.right, rtGrid.bottom);
     DrawText(hDC, _T("To Paint this rectangle with Solid Brush"), -1, &rtGrid, DT_VCENTER|DT_CENTER|DT_SINGLELINE);
 
     SelectObject(hDC, hOldBrush);
     RestoreDC(hDC, nSavedDC);
 
     return;
 }

2. HBRUSH CreatePatternBrush(HBITMAP hBitmap)

hBitmap -- 位图

创建指定位图的画刷，若位图小于绘图区时位图将平铺到整个区域;

 void CDemoWnd::DemoPatternBrush(HDC hDC, RECT& rtGrid)
 {
     int nSavedDC = SaveDC(hDC);
 
     HBITMAP hBmp        = LoadBitmap(GetModuleHandle(NULL), MAKEINTRESOURCE(IDB_PATTERN));
     HBRUSH  hBrush        = CreatePatternBrush(hBmp);
     HBRUSH  hOldBrush    = (HBRUSH)SelectObject(hDC, hBrush);
 
     InflateRect(&rtGrid, -5, -5);
     Rectangle(hDC, rtGrid.left, rtGrid.top, rtGrid.right, rtGrid.bottom);
 
     SetBkColor(hDC, RGB(255, 0, 255));
     DrawText(hDC, _T("To Paint this rectangle with Pattern Brush"), -1, &rtGrid, DT_VCENTER|DT_CENTER|DT_SINGLELINE);
 
     SelectObject(hDC, hOldBrush);
     DeleteObject(hBmp);
     DeleteObject(hBrush);
 
     RestoreDC(hDC, nSavedDC);
 
     return;
 }

3. HBRUSH CreateHatchBrush(int nStyle, COLORREF crColor)

nStyle -- 画刷风格

HS_BDIAGONAL 45-degree upward left-to-right hatch

HS_CROSS Horizontal and vertical crosshatch

HS_DIAGCROSS 45-degree crosshatch

HS_FDIAGONAL 45-degree downward left-to-right hatch

HS_HORIZONTAL Horizontal hatch

HS_VERTICAL Vertical hatch

crColor -- 画刷颜色

创建特定风格及颜色的画笔

 void CDemoWnd::DemoHatchBrush(HDC hDC, RECT& rtGrid)
 {
     int nSavedDC = SaveDC(hDC);
 
     const int nHatchType[] = {
         HS_BDIAGONAL,    // 45-degree upward left-to-right hatch
         HS_CROSS,        // Horizontal and vertical crosshatch 
         HS_DIAGCROSS,    // 45-degree crosshatch 
         HS_FDIAGONAL,    // 45-degree downward left-to-right hatch 
         HS_HORIZONTAL,    // Horizontal hatch 
         HS_VERTICAL        // Vertical hatch
     };
 
     InflateRect(&rtGrid, -5, -5);
 
     const int nBlank        = 10;
     const int nBlockCount    = sizeof(nHatchType) / sizeof(*nHatchType);
     const int nBlockWidth    = (rtGrid.right - rtGrid.left) / nBlockCount; 
 
     for (int ii = 0; ii < nBlockCount; ii++)
     {
         HBRUSH hBrush = CreateHatchBrush(nHatchType[ii], RGB(30, 33, 120));
         HBRUSH hOldBrush = (HBRUSH)SelectObject(hDC, hBrush);
         
         int nLeft = rtGrid.left + ii * nBlockWidth;
         Rectangle(hDC, nLeft + nBlank, rtGrid.top, nLeft + nBlockWidth, rtGrid.bottom);
 
         SelectObject(hDC, hOldBrush);
         DeleteObject(hBrush);
     }
 
     SetBkColor(hDC, RGB(128, 128, 0));
     DrawText(hDC, _T("To Paint this rectangle with Hatch Brush"), -1, &rtGrid, DT_VCENTER|DT_CENTER|DT_SINGLELINE);
 
     RestoreDC(hDC, nSavedDC);
 }

4. HBRUSH CreateBrushIndirect(LOGBRUSH LogBrush)

LogBrush – 逻辑画刷

  typedef struct tagLOGBRUSH { 
          UINT     lbStyle; 
          COLORREF lbColor; 
          LONG     lbHatch; 
     } LOGBRUSH, *PLOGBRUSH;

此方法除可创建以上3种画刷风格外还支持其他风格和样式(LOGBRUSH 功能比较使用比较复杂详见MSDN

void CDemoWnd::DemoKindOfBrush(HDC hDC, RECT& rtGrid)

{

    int nSavedDC = SaveDC(hDC);

    InflateRect(&rtGrid, -5, -5);

    const int nBlockCount    = 4;

    const int nBlank        = 10;

    const int nBlockW        = (rtGrid.right - rtGrid.left) / nBlockCount;

    RECT rtBlocks[nBlockCount];

    for (int ii = 0; ii < nBlockCount; ii++)

    {

        int nLeft = rtGrid.left + ii * nBlockW;

        SetRect(&rtBlocks[ii], nLeft + ((0 != ii) ? nBlank : 0), rtGrid.top, nLeft + nBlockW, rtGrid.bottom);

    }

    LOGBRUSH LogBrush[nBlockCount];

    //--: Solid Brush

    LogBrush[0].lbStyle    = BS_SOLID;

    LogBrush[0].lbColor    = RGB(234, 233, 21);

    LogBrush[0].lbHatch    = 0;

    //--: Pattern Brush

    LogBrush[1].lbStyle    = BS_PATTERN;

    LogBrush[1].lbColor = DIB_RGB_COLORS;

    LogBrush[1].lbHatch = (ULONG_PTR)LoadBitmap(GetModuleHandle(NULL), MAKEINTRESOURCE(IDB_PATTERN));

    //--: Hatch Brush

    LogBrush[2].lbStyle = BS_HATCHED;

    LogBrush[2].lbColor = RGB(234, 233, 21);

    LogBrush[2].lbHatch = HS_CROSS;

    //--: Transparent Brush

    LogBrush[3].lbStyle = BS_NULL;

    LogBrush[3].lbColor = 0;

    LogBrush[3].lbHatch = 0;

    for (int ii = 0; ii < nBlockCount; ii++)

    {    

        HBRUSH hBrush     = CreateBrushIndirect(&LogBrush[ii]);

        HBRUSH hOldBrush = (HBRUSH)SelectObject(hDC, hBrush);        

        Rectangle(hDC, rtBlocks[ii].left, rtBlocks[ii].top, rtBlocks[ii].right, rtBlocks[ii].bottom);

        SelectObject(hDC, hOldBrush);

        DeleteObject(hBrush);

    }

    DeleteObject((HBITMAP)LogBrush[1].lbHatch);

    SetBkColor(hDC, RGB(128, 128, 128));

    DrawText(hDC, _T("To Paint this rectangle with a kind of brush"), -1, &rtGrid, DT_VCENTER|DT_CENTER|DT_SINGLELINE);

    RestoreDC(hDC, nSavedDC);

    return;

}

二、画刷的使用

画刷与其他的GDI绘图对象一样，创建画刷后都须先通过SelectObject函数选入设备DC中，当GDI在当前设备环境中绘制图形时它将使用被选入的画刷进行喷绘.

    HBRUSH hBrush     = CreateSolidBrush(RGB(255, 128, 128));

    HBRUSH hOldBrush = (HBRUSH)SelectObject(hDC, hBrush);

    Rectangle(hDC, rtGrid.left, rtGrid.top, rtGrid.right, rtGrid.bottom);

    SelectObject(hDC, hOldBrush);

三、常用方法

COLORREF SetDCBrushColor(HDC hDC, COLORREF crColor)

设置当前默认的画刷颜色，使用此函数前如画笔一样先将备用画刷选入设备环境中如: SelectObject(hDC, GetStockObject(DC_BRUSH));

注: 在本例中我们使用另外二个DC函数:

int SaveDC(HDC ) 保存此函数调用前的DC设备环境，并返回保存的次数以备后期恢复

BOOL RestoreDC(HDC hDC, int nSavedDC) 恢复第几次保存的DC设备环境

通常使用时两函数都成对使用.

演示代码