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。
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, （Sources@SuperMain.com ，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
#include <afxctl.h>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;
}
