GDI 总结一 CBitmap类

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CBitmap类：

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                                                                       };

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;

1 装载已导入工程的位图资源

// 装载位图    CBitmap bmp;  bmp.LoadBitmap(IDB_BITMAP);

2 装载位图文件

为了能让CBitmap能够装载位图文件，必须调用API函数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  );

装载：

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);

将装载后得到的HBITMAP资源句柄与 CBitmap 对象相连

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

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

3 显示位图

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 删除资源

错误方式：

CBitmap bmp;  bmp.LoadBitmap(IDB_BITMAP);    CBitmap *pOld=pDC->SelectObject(&bmp);    // 此时位图对象还在pDC中，因此不能删除  下面的语句是错误的  bmp.DeleteObject();

正确方式：

CBitmap bmp;  bmp.LoadBitmap(IDB_BITMAP);    CBitmap *pOld=pDC->SelectObject(&bmp);    // 此时位图对象还在pDC中，因此不能马上删除  // 而是先将位图从DC中选出 然后再删除  pDC->SelectObject(pOld);  bmp.DeleteObject();

5 CBitmap 析构

当CBitmap作为局部变量在其退出作用范围后，会发生析构，这时候CBitmap会将其对应的位图资源（hBitmap ）释放掉。

若想继续使用该位图资源hBitmap，则在退出作用范围前，应将位图资源hBitmap和CBitmap对象通过Detach()函数进行分离

HBITMAP  CMyClass::Load()  {      CBitmap bmp;      bmp.LoadBitmap(IDB_BITMAP);        // 通过Detach 将资源与对象分离，这样bmp析构后，资源仍存在        // 否则 ，bmp析构时，会将位图资源一起析构掉，这样出了局部范围外，就不可再使用这个位图资源了      return bmp.Detach();  }

6 在仅获得HBITMAP资源句柄情况下，如何获得这个资源的BITMAP信息

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

7 在内存中开辟资源空间将原图保存到内存中

//-------------------在内存中建立区域以存放所得位图-------------------    // hBitmapSrc 为 CBitmap中保存的矩形原图资源句柄                          // hDC 句柄                                                               // 在内存中开辟位图资源，用以保存原图                                     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;

ON_MESSAGE(WM_PIC,OnPic)

(theApp.m_pMainWnd)->PostMessage(WM_PIC,(WPARAM)CopyHBitmap(hBitmap,IMG_HDC),0);

void OnPic(HBITMAP hBitmap)

http://blog.csdn.net/shuilan0066/article/details/7079973

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