The usage of image processing class CBitmap in VC++

The usage of CBitmap in VC++

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
};

Father

CGdiObject

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
};

Load the bitmap resource

of the imported project

//  Loads a bitmap 

  CBitmap bmp;
  bmp.LoadBitmap(IDB_BITMAP);

Load the bitmap file

      must call the API function LoadImage

in order for CBitmap to be able to load bitmap files

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
);

Load: 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);

Connect the HBITMAP resource handle obtained after loading to CBitmap object

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

Or

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

3 displays bitmap

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 delete resource

CBitmap bmp;
  bmp.LoadBitmap(IDB_BITMAP);

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

  //  The bitmap object is still there pDC , so it cannot be deleted immediately 
  //  Instead, start with the bitmap DC selected   And then delete it 
  pDC->SelectObject(pOld);
  bmp.DeleteObject();

5 CBitmap destructor

When CBitmap, as a local variable, exits its scope, destruction occurs, and CBitmap releases its corresponding bitmap resource (hBitmap).

To continue using the bitmap resource hBitmap, separate the bitmap resource hBitmap and CBitmap objects through the Detach() function

before exiting the scope

HBITMAP  CMyClass::Load()

{

    CBitmap bmp;

    bmp.LoadBitmap(IDB_BITMAP);
    //  through Detach  Separate the resource from the object, so bmp After destruction, the resource still exists   

    //  Otherwise,   . bmp When destructing, the bitmap resource is destructed together, so that out of the local scope, the bitmap resource can no longer be used 

    return bmp.Detach();

}

6 how do I get BITMAP information

for HBITMAP resource if I only get the HBITMAP resource handle

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

7 create resource space in memory and save the original image to
in memory

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
};

0

Here's an example: saves images from the CBitmap class to the file

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

finally attached CBitmap,HBitmap,Bitmap distinction and contact

To load a one-bit graph, you can use LoadImage:

HANDLE LoadImage (HINSTANCE hinst, LPCTSTR lpszName, UINT uType, int cxDesired, int CyDesired, UINT fuLoad);

LoadImage can be used to load bitmaps, ICONS and the cursor

The size of the map to memory of the load graph can be specified at load time:

      cxDesired: specifies the width of the icon or cursor, in pixels. If this parameter is zero and LR_DEFAULTSIZE is not used in the fuLoad value, the function USES the current resource width.

cyDesired: specifies the height of the icon or cursor, in pixels. If this parameter is zero and LR_DEFAULTSIZE is not used in the parameter fuLoad value, then the function USES the current resource height.

The return value of LoadImage is a handle to the relevant resource. Because the bitmap is loaded, the returned handle is of type HBITMAP (cast).

Extended understanding of HBITMAP/CBitmap/BITMAP:

HBITMAP is a pointer to bitmap,

msdn: Handle to a bitmap typedef HANDLE HBITMAP;

CBitmap is the class that encapsulates bitmap in mfc.

: in the msdn

Encapsulates (including) a Windows device interface

BITMAP is a structure that encapsulates some information about bitmap. Defines the height, width, color format, and bit values of a logical bitmap.

MSDN: This structure defines type, width, height, color format, and bit of bitmap

The relationship between the three:

HBITMAP hBitmap;

CBitmap bitmap;

BITMAP bm;

// the following is the connection between the three:

bitmap. Attach (hBitmap); // the associated CBitmap

is obtained by HBITMAP

bitmap. GetBitmap (& bm); // the associated BITMAP
is obtained by CBitmap hBitmap = (HBITMAP) bitmap. GetSafeHandle (); // HBITMAP

is obtained by CBitmap

The BITMAP structure has the following form:

typedef struct tagBITMAP
{
        int           bmType;
        int         bmWidth; / /
wide       int         bmHeight; / / high
        int           bmWidthBytes;
        BYTE         bmPlanes;
        BYTE         bmBitsPixel;
        LPVOID bmBits;
}   BITMAP;

Attach/Detach:

  attach associates an C++ object with an WINDOWS object until the association is removed with detach.  
  if attach does not have detach after attach, C++ object is destroyed when WINDOWS object is destroyed.  
After   attach is finished, there will be a mapping between the pointer of C++ object and HWND of WINDOWS object.     edit. create (...).  
  and the mapping is permanent until the object dies.  
  can also return a pointer if it USES a function similar to GetDlgItem and can be cast. GetDlgItem is going to look in the table.  
  has two mapping tables, one permanent and one temporary.  
  objects created directly from C++ objects or the mapping of attach objects are placed in the permanent table, otherwise the mapping is created in the temporary table.  
  so GetDlgItem does not recommend that you save the returned pointer because it is difficult to ensure that your WINDOWS object is in the permanent table with the C++ object.  
  is automatically deleted in idle time if the map is placed in a temporary table.  
  USES attcah solely for the convenience of manipulating WINDOWS objects with the member functions of the MFC class.