GDI 总结一 CBitmap类

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;

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

 

 

 

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);
 }

     OR

 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)

 

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