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(ImgEdit);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接口来显示图像。由于MFC的CPictureHolder类是这个接口的一个封装，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
源代码
#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;
}
