用何种方式读取jpg?

Question

我是从网上接收jpeg数据，放入內存中，我如何把这些数据显示在对话框中！用什么控件显示，是不是要自己写控件！用何种方式显示，听说可用jpglib2,Ipicture,GDI+！可否给点相关的源码或例子！请赐教！

Answer 1

你说的那三种方法都不错，源码例子很容易在网上找啊。去www.vcbase.com

Answer 2

有没有用GDI+和IPicture的源码！哪位大侠给发一个！

Answer 3

个人推荐IPicture。
给你封装IPicture的一个类：
class CPicture  
{
public:
CPicture();
virtual ~CPicture();
protected:
IPicture *m_IPicture;
OLE_XSIZE_HIMETRIC  m_Height, m_Weight, m_Width;
public:
BOOL Load(HINSTANCE hInstance,LPCTSTR lpszResourceName, LPCSTR ResourceType);
BOOL Load(CString sFilePathName);
BOOL LoadPictureData(BYTE *pBuffer, int nSize);
BOOL Show(CDC* pDC, LPRECT pDrawRect = NULL, LPRECT pSrcRect = NULL);
BOOL SaveAsBitmap(CString sFilePathName);
BOOL UpdateSizeOnDC(CDC *pDC);
BOOL CreateFromIcon(HICON hIcon);
BOOL CreateFromBitmap(HBITMAP hBitmap);
inline UINT GetWidth() { return m_Width;}
inline UINT GetHeight() { return m_Height;}
protected:
void GetImageSize();
void UnLoadPicture();
void FreePictureData();
};

Answer 4

#include <Shlwapi.h>#pragma comment (lib, "Shlwapi")#define HIMETRIC_INCH 2540
#define ERROR_TITLE "CPicture Error" // Error Title (Related To This Class)...//-----------------------------------------------------------------------------
CPicture::CPicture()
//=============================================================================
{
m_IPicture = NULL;
m_Height = 0;
m_Weight = 0;
m_Width = 0;
}//-----------------------------------------------------------------------------
// Does:   Destructor - Free Data And Information From The CPicture Object
// ~~~~
//
//-----------------------------------------------------------------------------
CPicture::~CPicture()
//=============================================================================
{
if(m_IPicture != NULL) FreePictureData(); // Important - Avoid Leaks...
}
//-----------------------------------------------------------------------------
// 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::FreePictureData()
//=============================================================================
{
if(m_IPicture != NULL)
{
m_IPicture->Release();
m_IPicture = NULL;
m_Height = 0;
m_Weight = 0;
m_Width = 0;
}
}//-----------------------------------------------------------------------------
// 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_IPicture != NULL) FreePictureData(); // 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) m_Weight = nSize; // Update Picture Size Info...
GetImageSize();
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_IPicture != NULL) FreePictureData(); // 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;
} m_Weight = nSize; // Update Picture Size Info...
GetImageSize();
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_IPicture)) == 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);
}

Answer 5

//-----------------------------------------------------------------------------
// 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...
// ~~~~~~
//-----------------------------------------------------------------------------
//=============================================================================
#define HIMETRIC_INCH 2540
BOOL CPicture::Show(CDC* pDC, LPRECT pDrawRect, LPRECT pSrcRect/*=NULL*/)
{
    if (pDC == NULL || m_IPicture == NULL) return FALSE;
    CRect DrawRect, SrcRect;
    OLE_XSIZE_HIMETRIC Width, Height;
    m_IPicture->get_Width(&Width);
    m_IPicture->get_Height(&Height); if(pSrcRect)
{
SrcRect=*pSrcRect;
// convert pixels to himetric 
SrcRect.bottom =MulDiv(SrcRect.bottom, HIMETRIC_INCH,GetDeviceCaps(pDC->m_hDC, LOGPIXELSX));
SrcRect.left =MulDiv(SrcRect.left, HIMETRIC_INCH,GetDeviceCaps(pDC->m_hDC, LOGPIXELSX));
SrcRect.right =MulDiv(SrcRect.right, HIMETRIC_INCH,GetDeviceCaps(pDC->m_hDC, LOGPIXELSX));
SrcRect.top =MulDiv(SrcRect.top, HIMETRIC_INCH,GetDeviceCaps(pDC->m_hDC, LOGPIXELSX));
}
else
SrcRect.SetRect(CPoint(0,0), CPoint(Width, Height));
if (NULL != pDrawRect)
{
DrawRect = *pDrawRect;
}
else
DrawRect.SetRect(CPoint(0, 0), CPoint(m_Width, m_Height));

DrawRect.NormalizeRect();
SrcRect.NormalizeRect();
    HRESULT hrP = NULL;
    hrP = m_IPicture->Render(pDC->m_hDC,
                      DrawRect.left,                  // Left
                      DrawRect.top,                   // Top
                      DrawRect.Width(), // Right
                      DrawRect.Height(), // Bottom
                      SrcRect.left,
                      SrcRect.Height(),
                      SrcRect.Width(),
                      -SrcRect.Height(),
                      &DrawRect);
    if (SUCCEEDED(hrP)) return(TRUE);
AfxThrowMemoryException();
    return(FALSE);
}//-----------------------------------------------------------------------------
// 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_IPicture->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);
}//-----------------------------------------------------------------------------
// Does:   Get The Original Picture Pixel Size (Ignor What Current DC Is Using)
// ~~~~    Pointer To a Device Context Is Needed For Pixel Calculation,
//
//         Also Updates The Class's Height And Width Properties,
//         (Coz Till Now We Had No Device Context To Work With...96 DPI Assumed)
//
// InPut:  The Client DC (Needed To Check The Size Of The Pixels)
// ~~~~~
//
// OutPut: TRUE If Succeeded...
// ~~~~~~
//-----------------------------------------------------------------------------
BOOL CPicture::UpdateSizeOnDC(CDC *pDC)
{
if(pDC == NULL || m_IPicture == NULL) { m_Height = 0; m_Width = 0; return(FALSE); }
    m_IPicture->get_Height(&m_Height);
    m_IPicture->get_Width(&m_Width); // Get Current DPI - Dot Per Inch
    int CurrentDPI_X = pDC->GetDeviceCaps(LOGPIXELSX);
    int CurrentDPI_Y = pDC->GetDeviceCaps(LOGPIXELSY); // Use a "Standard" Print (When Printing)
    if(pDC->IsPrinting())
{
CurrentDPI_X = 96;
        CurrentDPI_Y = 96;
}
    m_Height = MulDiv(m_Height, CurrentDPI_Y, HIMETRIC_INCH);
    m_Width  = MulDiv(m_Width,  CurrentDPI_X, HIMETRIC_INCH);
    return(TRUE);
}BOOL CPicture::CreateFromIcon(HICON hIcon)
{
BOOL bResult=FALSE;
if(hIcon)
{
PICTDESC desc;
desc.cbSizeofstruct = sizeof(PICTDESC);
desc.picType = PICTYPE_ICON;
desc.icon.hicon= hIcon;
m_Weight = 0;
if(FAILED(::OleCreatePictureIndirect(&desc,IID_IPicture,FALSE,(LPVOID*)&m_IPicture)))
bResult=FALSE;
}
else
bResult=TRUE;
GetImageSize();
return bResult;
}BOOL CPicture::CreateFromBitmap(HBITMAP hBitmap)
{ 
BOOL bResult=FALSE;
if(hBitmap)
{
PICTDESC desc;
desc.cbSizeofstruct = sizeof(PICTDESC);
desc.picType = PICTYPE_BITMAP;
desc.bmp.hbitmap = hBitmap;
desc.bmp.hpal = 0;
m_Weight = 0;
if(FAILED(::OleCreatePictureIndirect(&desc,IID_IPicture,FALSE,(LPVOID*)&m_IPicture)))
bResult=FALSE;
else
bResult=TRUE;
}
GetImageSize();
return bResult;
}void CPicture::GetImageSize()
{ 
if(m_IPicture != NULL){// Do Not Try To Read From Memory That Is Not Exist...
m_IPicture->get_Height(&m_Height);
m_IPicture->get_Width(&m_Width);
// Calculate Its Size On a "Standard" (96 DPI) Device Context
m_Height = MulDiv(m_Height, 96, HIMETRIC_INCH);
m_Width  = MulDiv(m_Width,  96, HIMETRIC_INCH);
}
else
{// Picture Data Is Not a Known Picture Type
m_Height = 0;
m_Width = 0;
m_Weight=0;
}
}void CPicture::UnLoadPicture()
{
FreePictureData();
}

Answer 6

使用GDI+的速度也不见得多快，主要是方便，如果是正式的广泛使用的软件建议不要使用其他的相关类库，涉及的版权问题不说，结构也不好！

Answer 7

   直接用CImage即可,十分简单。
#include "atlimage.h"参见：MSDN:  Shared Visual C++ Classes Reference