使用IPicture的OLE实现读取和显示BMP,GIF,JPG,ICO,EMF,WMF图像

作者的话：GDI+看起来是更好的解决方案，但是IPicture的OLE实现更简单。

问题的起源

很久以来，我都被一个问题困扰。关于程序中显示图像的问题，我在网络上搜索了很长时间，找到了无数的解决方案，比如分析文件格式,直接读取文件的;用控件的(柯达的ImgEdit控件);以及不知道内部实现方法的库（ImageLoad）。而我找到的方法大都不容易使用，特别是那些直接按位读取图像的。很多时候我不得不为每种文件格式写一段代码。

目前我的解决方案

在使用了多种图形显示方案之后，我决定使用微软提供的IPicture的OLE实现来显示图像。由于MFC的CPictureHolder类是这个实现的一个封装，而且自带了从图像句柄读入图形的功能，所以我的工作以CPictureHolder类为基础。要是你不喜欢MFC的话，你可以把CPictureHolder类的代码从MFC的源代码里面分离出来单独使用。

CPictureHolder类的设计目的是实现ActiveX控件的Picture属性，允许用户在控件中显示图像。作为默认的Picture属性，开发者可以指定一个位图(Bitmap)，图标(Icon)，或者图元文件(Metafile)来显示。虽然微软的文档中并未说明支持JPEG格式的图像，但是经过我的测试，在Windows98以上，以及Windows2000中，它实际上是支持JPEG格式的，根据微软的文档，支持的图像格式有BMP,DIB,WMF，ICO。笔者并未测试其他图像格式是否被支持，例如PNG、GIF、PCX等等，有兴趣的读者可以去自己测试一下。(据111222的文档http://www.csdn.net/develop/read_article.asp?id=10632，也支持GIF格式)

由于CPictureHolder类并未实现从文件/资源/内存读入图像，使用起来很不方便，所以我扩展了这个类以支持上述功能。部分工作基于Dr. Yovav Gad, （[email protected] ，www.SuperMain.com）和http://www.thecodeproject.com/bitmap/cpicture.asp的代码。

要使用CPictureHolder类，必须先包含afxctl.h

源代码

#include
class CPicture:public CPictureHolder
{
public:
 BOOL Load(CString sFilePathName);//从文件读取图像
 BOOL Load(HINSTANCE hInstance,LPCTSTR lpszResourceName, LPCSTR ResourceType);//从资源读取图像
 BOOL LoadPictureData(BYTE* pBuffer, int nSize);//从内存读取图像
 BOOL SaveAsBitmap(CString sFilePathName);//写入到BMP文件
 void Render(CDC* pDC, LPRECT pDrawRect/*目标矩形，单位是逻辑坐标单位*/, LPRECT

pSrcRect=NULL/*来源矩形，单位是0.01毫米,如果为空，则拉伸整个图像到目标矩形*/,LPCRECT prcWBounds=NULL/*图元文件专用，绑定矩形*/);//在给定的DC上画图，
 CPicture();
 virtual ~CPicture();
 void  UnloadPicture();//释放图像，作用同CPictureHolder::~CPictureHolder()
public:
 LONG      get_Height(); // 以0.01毫米为单位的图像高度
 LONG      get_Width();  // 以0.01毫米为单位的图像宽度
};

//-----------------------------------------------------------------------------
// Does:   Free The Allocated Memory That Holdes The IPicture Interface Data
// ~~~~    And Clear Picture Information
//
// Note:   This Might Also Be Useful If U Only Need To Show The Picture Once
// ~~~~~   Or If U Copy The Picture To The Device Context, So It Can Still
//         Remain On Screen - But IPicture Data Is Not Needed No More
//
//-----------------------------------------------------------------------------
void CPicture::UnloadPicture()
//=============================================================================
{
 if(m_pPict != NULL){
  m_pPict->Release();
  m_pPict = NULL;
 }
}
//-----------------------------------------------------------------------------
// Does:   Open a Resource And Load It Into IPicture (Interface)
// ~~~~    (.BMP .DIB .EMF .GIF .ICO .JPG .WMF)
//
// Note:   When Adding a Bitmap Resource It Would Automatically Show On "Bitmap"
// ~~~~    This NOT Good Coz We Need To Load It From a Custom Resource "BMP"
//         To Add a Custom Rresource: Import Resource -> Open As -> Custom
//         (Both .BMP And .DIB Should Be Found Under "BMP")
//
// InPut:  ResourceName - As a UINT Defined (Example: IDR_PICTURE_RESOURCE)
// ~~~~~   ResourceType - Type Name (Example: "JPG")
//
// OutPut: TRUE If Succeeded...
// ~~~~~~
//-----------------------------------------------------------------------------
BOOL CPicture::Load(HINSTANCE hInstance,LPCTSTR lpszResourceName, LPCSTR ResourceType)
//=============================================================================
{
 HGLOBAL  hGlobal = NULL;
 HRSRC  hSource = NULL;
 LPVOID  lpVoid  = NULL;
 int   nSize   = 0;
 BOOL  bResult=FALSE;
 if(m_pPict != NULL) UnloadPicture(); // Important - Avoid Leaks...

 hSource = FindResource(hInstance, lpszResourceName, ResourceType);

 if(hSource == NULL)
  {
  HWND hWnd = AfxGetApp()->GetMainWnd()->m_hWnd;
  MessageBoxEx(hWnd, "FindResource() Failed/t", ERROR_TITLE, MB_OK | MB_ICONSTOP, LANG_ENGLISH);
  return(FALSE);
  }

 hGlobal = LoadResource(hInstance, hSource);
 if(hGlobal == NULL)
  {
  HWND hWnd = AfxGetApp()->GetMainWnd()->m_hWnd;
  MessageBoxEx(hWnd, "LoadResource() Failed/t", ERROR_TITLE, MB_OK | MB_ICONSTOP, LANG_ENGLISH);
  return(FALSE);
  }

 lpVoid = LockResource(hGlobal);
 if(lpVoid == NULL)
  {
  HWND hWnd = AfxGetApp()->GetMainWnd()->m_hWnd;
  MessageBoxEx(hWnd, "LockResource() Failed/t", ERROR_TITLE, MB_OK | MB_ICONSTOP, LANG_ENGLISH);
  return(FALSE);
  }

 nSize = (UINT)SizeofResource(hInstance, hSource);
 if(LoadPictureData((BYTE*)hGlobal, nSize)) bResult = TRUE;

 UnlockResource(hGlobal); // 16Bit Windows Needs This
 FreeResource(hGlobal); // 16Bit Windows Needs This (32Bit - Automatic Release)
 return(bResult);
}

//-----------------------------------------------------------------------------
// Does:   Open a File And Load It Into IPicture (Interface)
// ~~~~    (.BMP .DIB .EMF .GIF .ICO .JPG .WMF)
//
// InPut:  sFilePathName - Path And FileName Target To Save
// ~~~~~  
//
// OutPut: TRUE If Succeeded...
// ~~~~~~
//-----------------------------------------------------------------------------
BOOL CPicture::Load(CString sFilePathName)
//=============================================================================
{
 if(!PathFileExists(sFilePathName))return FALSE;
 BOOL bResult = FALSE;
 CFile PictureFile;
 CFileException e;
 int nSize = 0;

 if(m_pPict != NULL) UnloadPicture(); // Important - Avoid Leaks...

 if(PictureFile.Open(sFilePathName, CFile::modeRead | CFile::typeBinary, &e))
  {
  nSize = PictureFile.GetLength();
  BYTE* pBuffer = new BYTE[nSize];
 
  if(PictureFile.Read(pBuffer, nSize) > 0)
   {
   if(LoadPictureData(pBuffer, nSize)) bResult = TRUE;
   }

  PictureFile.Close();
  delete [] pBuffer;
  }
 else // Open Failed...
  {
  TCHAR szCause[255];
  e.GetErrorMessage(szCause, 255, NULL);
  HWND hWnd = AfxGetApp()->GetMainWnd()->m_hWnd;
  MessageBoxEx(hWnd, szCause, ERROR_TITLE, MB_OK | MB_ICONSTOP, LANG_ENGLISH);
  bResult = FALSE;
  }
 return(bResult);
}

//-----------------------------------------------------------------------------
// Does:   Read The Picture Data From a Source (File / Resource)
// ~~~~    And Load It Into The Current IPicture Object In Use
//
// InPut:  Buffer Of Data Source (File / Resource) And Its Size
// ~~~~~  
//
// OutPut: Feed The IPicture Object With The Picture Data
// ~~~~~~  (Use Draw Functions To Show It On a Device Context)
//         TRUE If Succeeded...
//-----------------------------------------------------------------------------
BOOL CPicture::LoadPictureData(BYTE *pBuffer, int nSize)
//=============================================================================
{
 BOOL bResult = FALSE;
 HGLOBAL hGlobal = GlobalAlloc(GMEM_MOVEABLE, nSize);

 if(hGlobal == NULL)
  {
  HWND hWnd = AfxGetApp()->GetMainWnd()->m_hWnd;
  MessageBoxEx(hWnd, "Can not allocate enough memory/t", ERROR_TITLE, MB_OK | MB_ICONSTOP, LANG_ENGLISH);
  return(FALSE);
  }

 void* pData = GlobalLock(hGlobal);
 memcpy(pData, pBuffer, nSize);
 GlobalUnlock(hGlobal);

 IStream* pStream = NULL;

 if(CreateStreamOnHGlobal(hGlobal, TRUE, &pStream) == S_OK)
  {
  HRESULT hr;
  if((hr = OleLoadPicture(pStream, nSize, FALSE, IID_IPicture, (LPVOID *)&m_pPict)) == E_NOINTERFACE)
   {
   HWND hWnd = AfxGetApp()->GetMainWnd()->m_hWnd;
   MessageBoxEx(hWnd, "IPicture interface is not supported/t", ERROR_TITLE, MB_OK | MB_ICONSTOP, LANG_ENGLISH);
   return(FALSE);
   }
  else // S_OK
   {
   pStream->Release();
   pStream = NULL;
   bResult = TRUE;
   
   }
  }

 FreeResource(hGlobal); // 16Bit Windows Needs This (32Bit - Automatic Release)

 return(bResult);
}

//-----------------------------------------------------------------------------
// Does:   Draw The Loaded Picture Direct To The Client DC
// ~~~~
//
// Note:   Bigger OR Smaller Dimentions Than The Original Picture Size
// ~~~~    Will Draw The Picture Streached To Its New Given NEW Dimentions...
//
// InPut:  pDC - Given DC To Draw On
// ~~~~~   pSrcRect- Dimentions Of The Picture To Draw From(As a Rectangle)
//   DrawRect - Dimentions Of The Picture To Draw To(As a Rectangle)
// OutPut: TRUE If Succeeded...
// ~~~~~~
//-----------------------------------------------------------------------------
//=============================================================================

void CPicture::Render(CDC* pDC, LPRECT pDrawRect, LPRECT pSrcRect/*=NULL*/,LPCRECT prcWBounds/*=NULL*/)
{
    if (pDC == NULL || m_pPict == NULL) return ;
   
 CRect recrDest(pDrawRect);

    long Width  = 0;
    long Height = 0;
    m_pPict->get_Width(&Width);
    m_pPict->get_Height(&Height);

 CRect SrcRect(0,0,Width,Height);

 if(pSrcRect){
  SrcRect=*pSrcRect;
 }
 CRect DrawRect(pDrawRect);
    HRESULT hrP = NULL;

    hrP = m_pPict->Render(pDC->m_hDC,
                      DrawRect.left,                  // Left
                      DrawRect.top,                   // Top
                      DrawRect.Width(), // Right
                      DrawRect.Height(), // Bottom
                      SrcRect.left,
                      SrcRect.top,
                      SrcRect.Width(),
                      SrcRect.Height(),
                      prcWBounds);

    if (SUCCEEDED(hrP)) return;
 AfxThrowMemoryException();
    return;
}//-----------------------------------------------------------------------------
// Does:   Saves The Picture That Is Stored In The IPicture Object As a Bitmap
// ~~~~    (Converts From Any Known Picture Type To a Bitmap / Icon File)
//
// InPut:  sFilePathName - Path And FileName Target To Save
// ~~~~~
//
// OutPut: TRUE If Succeeded...
// ~~~~~~
//-----------------------------------------------------------------------------
BOOL CPicture::SaveAsBitmap(CString sFilePathName)
//=============================================================================
{
 BOOL bResult = FALSE;
 ILockBytes *Buffer = 0;
 IStorage   *pStorage = 0;
 IStream    *FileStream = 0;
 BYTE    *BufferBytes;
 STATSTG  BytesStatistics;
 DWORD  OutData;
 long  OutStream;
 CFile  BitmapFile; CFileException e;
 double  SkipFloat = 0;
 DWORD  ByteSkip = 0;
 _ULARGE_INTEGER RealData;

 CreateILockBytesOnHGlobal(NULL, TRUE, &Buffer); // Create ILockBytes Buffer

 HRESULT hr = ::StgCreateDocfileOnILockBytes(Buffer,
     STGM_SHARE_EXCLUSIVE | STGM_CREATE | STGM_READWRITE, 0, &pStorage);

 hr = pStorage->CreateStream(L"PICTURE",
   STGM_SHARE_EXCLUSIVE | STGM_CREATE | STGM_READWRITE, 0, 0, &FileStream);

 m_pPict->SaveAsFile(FileStream, TRUE, &OutStream); // Copy Data Stream
 FileStream->Release();
 pStorage->Release();
 Buffer->Flush();

 // Get Statistics For Final Size Of Byte Array
 Buffer->Stat(&BytesStatistics, STATFLAG_NONAME);

 // Cut UnNeeded Data Coming From SaveAsFile() (Leave Only "Pure" Picture Data)
 SkipFloat = (double(OutStream) / 512); // Must Be In a 512 Blocks...
 if(SkipFloat > DWORD(SkipFloat)) ByteSkip = (DWORD)SkipFloat + 1;
 else ByteSkip = (DWORD)SkipFloat;
 ByteSkip = ByteSkip * 512; // Must Be In a 512 Blocks...
 
 // Find Difference Between The Two Values
 ByteSkip = (DWORD)(BytesStatistics.cbSize.QuadPart - ByteSkip);

 // Allocate Only The "Pure" Picture Data
 RealData.LowPart = 0;
 RealData.HighPart = 0;
 RealData.QuadPart = ByteSkip;
 BufferBytes = (BYTE*)malloc(OutStream);
 if(BufferBytes == NULL)
  {
  Buffer->Release();
  HWND hWnd = AfxGetApp()->GetMainWnd()->m_hWnd;
  MessageBoxEx(hWnd, "Can not allocate enough memory/t", ERROR_TITLE, MB_OK | MB_ICONSTOP, LANG_ENGLISH);
  }

 Buffer->ReadAt(RealData, BufferBytes, OutStream, &OutData);

 if(BitmapFile.Open(sFilePathName, CFile::typeBinary | CFile::modeCreate | CFile::modeWrite, &e))
  {
  BitmapFile.Write(BufferBytes, OutData);
  BitmapFile.Close();
  bResult = TRUE;
  }
 else // Write File Failed...
  {
  TCHAR szCause[255];
  e.GetErrorMessage(szCause, 255, NULL);
  HWND hWnd = AfxGetApp()->GetMainWnd()->m_hWnd;
  MessageBoxEx(hWnd, szCause, ERROR_TITLE, MB_OK | MB_ICONSTOP, LANG_ENGLISH);
  bResult = FALSE;
  }
 
 Buffer->Release();
 free(BufferBytes);

 return(bResult);
}

LONG      CPicture::get_Height()
{
 LONG     nHeight = 0;

 if (m_pPict != NULL)
 {
  m_pPict->get_Height(&nHeight);
 }

 return nHeight;
}
LONG      CPicture::get_Width()
{
 LONG     nWidth = 0;

 if (m_pPict != NULL)
 {
  m_pPict->get_Width(&nWidth);
 }

 return nWidth;

}