VC++ GDI 總結 一一 CBitmap類，gdicbitmap

VC++ GDI 總結 一一 CBitmap類，gdicbitmap

class CBitmap : public CGdiObject
{
    DECLARE_DYNAMIC(CBitmap)

public:
    static CBitmap* PASCAL FromHandle(HBITMAP hBitmap);

// Constructors
    CBitmap();

    BOOL LoadBitmap(LPCTSTR lpszResourceName);
    BOOL LoadBitmap(UINT nIDResource);
    BOOL LoadOEMBitmap(UINT nIDBitmap); // for OBM_/OCR_/OIC_
#ifndef _AFX_NO_AFXCMN_SUPPORT
    BOOL LoadMappedBitmap(UINT nIDBitmap, UINT nFlags = 0,
        LPCOLORMAP lpColorMap = NULL, int nMapSize = 0);
#endif
    BOOL CreateBitmap(int nWidth, int nHeight, UINT nPlanes, UINT nBitcount,
            const void* lpBits);
    BOOL CreateBitmapIndirect(LPBITMAP lpBitmap);
    BOOL CreateCompatibleBitmap(CDC* pDC, int nWidth, int nHeight);
    BOOL CreateDiscardableBitmap(CDC* pDC, int nWidth, int nHeight);

// Attributes
    operator HBITMAP() const;
    int GetBitmap(BITMAP* pBitMap);

// Operations
    DWORD SetBitmapBits(DWORD dwCount, const void* lpBits);
    DWORD GetBitmapBits(DWORD dwCount, LPVOID lpBits) const;
    CSize SetBitmapDimension(int nWidth, int nHeight);
    CSize GetBitmapDimension() const;

// Implementation
public:
    virtual ~CBitmap();
#ifdef _DEBUG
    virtual void Dump(CDumpContext& dc) const;
#endif
};

父

class CGdiObject : public CObject
{
    DECLARE_DYNCREATE(CGdiObject)
public:

// Attributes
    HGDIOBJ m_hObject;                  // must be first data member
    operator HGDIOBJ() const;
    HGDIOBJ GetSafeHandle() const;

    static CGdiObject* PASCAL FromHandle(HGDIOBJ hObject);
    static void PASCAL DeleteTempMap();
    BOOL Attach(HGDIOBJ hObject);
    HGDIOBJ Detach();

// Constructors
    CGdiObject(); // must Create a derived class object
    BOOL DeleteObject();

// Operations
#pragma push_macro("GetObject")
#undef GetObject
    int _AFX_FUNCNAME(GetObject)(int nCount, LPVOID lpObject) const;
    int GetObject(int nCount, LPVOID lpObject) const;
#pragma pop_macro("GetObject")
    UINT GetObjectType() const;
    BOOL CreateStockObject(int nIndex);
    BOOL UnrealizeObject();
    BOOL operator==(const CGdiObject& obj) const;
    BOOL operator!=(const CGdiObject& obj) const;

// Implementation
public:
    virtual ~CGdiObject();
#ifdef _DEBUG
    virtual void Dump(CDumpContext& dc) const;
    virtual void AssertValid() const;
#endif
};

1 裝載已導入工程的位圖資源

// 裝載位圖

    CBitmap bmp;
    bmp.LoadBitmap(IDB_BITMAP);

2 裝載位圖文件

    為了能讓CBitmap能夠裝載位圖文件，必須調用API函數LoadImage

HANDLE LoadImage(
  HINSTANCE hinst,   // handle of the instance containing the image
  LPCTSTR lpszName,  // name or identifier of image
  UINT uType,        // type of image
  int cxDesired,     // desired width
  int cyDesired,     // desired height
  UINT fuLoad        // load flags
);

裝載： Example 1:

HBITMAP hBmp = (HBITMAP)LoadImage(NULL,
        m_fileName,
        IMAGE_BITMAP, 
        0, 0, 
        LR_LOADFROMFILE | LR_DEFAULTCOLOR | LR_DEFAULTSIZE);

Example 2:

HBITMAP    hBmp = (HBITMAP)::LoadImage(AfxGetInstanceHandle(),
        "BG.bmp",
        IMAGE_BITMAP,
        0,0,
        LR_LOADFROMFILE);

將裝載後得到的HBITMAP資源句柄 與 CBitmap 對象 相連

if (hBmp != NULL) {
        CBitmap *pBmp = CBitmap::FromHandle(hBmp);
    }

或

CBitmap bmp;
    if (hBmp != NULL) {
        bmp.DeleteObject();
        bmp.Attach(hBmp);    
    }

CBitmap bmp;
    bmp.LoadBitmap(IDB_BITMAP1);
    
    BITMAP bm;
    bmp.GetBitmap(&bm);

    CDC dc;
    dc.CreateCompatibleDC(pDC);
    CBitmap*pOldBmp=(CBitmap *)dc.SelectObject(&bmp);

    pDC->BitBlt(0,0,bm.bmWidth,bm.bmHeight,&dc,0,0,SRCCOPY);
    pDC->SelectObject(pOldBmp);

    bmp.DeleteObject();
    bmp.LoadBitmap(IDB_BITMAP2);

4 刪除資源

CBitmap bmp;
    bmp.LoadBitmap(IDB_BITMAP);

    CBitmap *pOld=pDC->SelectObject(&bmp);

    // 此時位圖對象還在pDC中，因此不能馬上刪除
    // 而是先將位圖從DC中選出 然後再刪除
    pDC->SelectObject(pOld);
    bmp.DeleteObject();

5 CBitmap 析構

當CBitmap作為局部變量 在其退出作用范圍後，會發生析構，這時候CBitmap會將其對應的位圖資源（hBitmap ）釋放掉。

若想繼續使用該位圖資源hBitmap，則在退出作用范圍前，應將位圖資源hBitmap和CBitmap對象通過Detach()函數進行分離

HBITMAP  CMyClass::Load()
{
    CBitmap bmp;
    bmp.LoadBitmap(IDB_BITMAP);

    // 通過Detach 將資源與對象分離，這樣bmp析構後，資源仍存在  
    // 否則 ，bmp析構時，會將位圖資源一起析構掉，這樣出了局部范圍外，就不可再使用這個位圖資源了
    return bmp.Detach();
}

6 在僅獲得HBITMAP資源句柄情況下，如何獲得這個資源的BITMAP信息

BITMAP bm;
GetObject(hBitmap,sizeof(BITMAP),&bm);

//-------------------在內存中建立區域以存放所得位圖-------------------
// hBitmapSrc 為 CBitmap中保存的矩形原圖資源句柄
// hDC 句柄   
// 在內存中開辟位圖資源，用以保存原圖
HBITMAP CopyHBitmap(HBITMAP hBitmapSrc,HDC hDC)
{
    
    BITMAP bm;
    HBITMAP hBitmapDst;
    HDC hdcSrc,hdcDst;

    GetObject(hBitmapSrc,sizeof(BITMAP),&bm);
    hBitmapDst=CreateCompatibleBitmap(hDC,bm.bmWidth,bm.bmHeight);

    hdcSrc=CreateCompatibleDC(hDC);
    hdcDst=CreateCompatibleDC(hDC);

    SelectObject(hdcSrc,hBitmapSrc); 
    SelectObject(hdcDst,hBitmapDst);

    BitBlt(hdcDst,0,0,bm.bmWidth,bm.bmHeight,hdcSrc,0,0,SRCCOPY);
    
    DeleteDC(hdcSrc);
    DeleteDC(hdcDst);    
    return hBitmapDst;

}