GDI 总结一 CBitmap类

CBitmap类：

 

class CBitmap : public CGdiObject{DECLARE_DYNAMIC(CBitmap)public:static CBitmap* PASCAL FromHandle(HBITMAP hBitmap);// ConstructorsCBitmap();BOOL LoadBitmap(LPCTSTR lpszResourceName);BOOL LoadBitmap(UINT nIDResource);BOOL LoadOEMBitmap(UINT nIDBitmap); // for OBM_/OCR_/OIC_#ifndef _AFX_NO_AFXCMN_SUPPORTBOOL LoadMappedBitmap(UINT nIDBitmap, UINT nFlags = 0,LPCOLORMAP lpColorMap = NULL, int nMapSize = 0);#endifBOOL 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);// Attributesoperator HBITMAP() const;int GetBitmap(BITMAP* pBitMap);// OperationsDWORD SetBitmapBits(DWORD dwCount, const void* lpBits);DWORD GetBitmapBits(DWORD dwCount, LPVOID lpBits) const;CSize SetBitmapDimension(int nWidth, int nHeight);CSize GetBitmapDimension() const;// Implementationpublic:virtual ~CBitmap();#ifdef _DEBUGvirtual void Dump(CDumpContext& dc) const;#endif};

 

class CGdiObject : public CObject{DECLARE_DYNCREATE(CGdiObject)public:// AttributesHGDIOBJ m_hObject;                  // must be first data memberoperator HGDIOBJ() const;HGDIOBJ GetSafeHandle() const;static CGdiObject* PASCAL FromHandle(HGDIOBJ hObject);static void PASCAL DeleteTempMap();BOOL Attach(HGDIOBJ hObject);HGDIOBJ Detach();// ConstructorsCGdiObject(); // must Create a derived class objectBOOL DeleteObject();// Operations#pragma push_macro("GetObject")#undef GetObjectint _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;// Implementationpublic:virtual ~CGdiObject();#ifdef _DEBUGvirtual 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:

    HBITMAPhBmp = (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)