在VC中怎样读jpg文件

[ferretzhu]

[Qinriwei]

一个函数，可以加载任何类型得图象啊。（也不能说任何，反正JPG、Gif、BMP都可以）
void LoadPictureFromFile(HDC hdc, LPCTSTR szFile, CBitmap *pBitmap, CSize &mSize)
{
// open file
HANDLE hFile = CreateFile(szFile, GENERIC_READ, 0, NULL, OPEN_EXISTING, 0, NULL);
_ASSERTE(INVALID_HANDLE_VALUE != hFile);

// get file size
DWORD dwFileSize = GetFileSize(hFile, NULL);
_ASSERTE(-1 != dwFileSize);

LPVOID pvData = NULL;
// alloc memory based on file size
HGLOBAL hGlobal = GlobalAlloc(GMEM_MOVEABLE, dwFileSize);
_ASSERTE(NULL != hGlobal);

pvData = GlobalLock(hGlobal);
_ASSERTE(NULL != pvData);

DWORD dwBytesRead = 0;
// read file and store in global memory
BOOL bRead = ReadFile(hFile, pvData, dwFileSize, &dwBytesRead, NULL);
_ASSERTE(FALSE != bRead);
GlobalUnlock(hGlobal);
CloseHandle(hFile);

LPSTREAM pstm = NULL;
// create IStream* from global memory
HRESULT hr = CreateStreamOnHGlobal(hGlobal, TRUE, &pstm);
_ASSERTE(SUCCEEDED(hr) && pstm);

// Create IPicture from image file
LPPICTURE gpPicture;

hr = ::OleLoadPicture(pstm, dwFileSize, FALSE, IID_IPicture, (LPVOID *)&gpPicture);

_ASSERTE(SUCCEEDED(hr) && gpPicture);
pstm->Release();

OLE_HANDLE m_picHandle;
/*
long hmWidth, hmHeight;
gpPicture->get_Width(&hmWidth);
gpPicture->get_Height(&hmHeight);
int nWidth = MulDiv(hmWidth, GetDeviceCaps(hdc, LOGPIXELSX), HIMETRIC_INCH);
int nHeight = MulDiv(hmHeight, GetDeviceCaps(hdc, LOGPIXELSY), HIMETRIC_INCH);
*/
gpPicture->get_Handle(&m_picHandle);
pBitmap->DeleteObject();
pBitmap->Attach((HGDIOBJ) m_picHandle);

BITMAP bm;
GetObject(pBitmap->m_hObject, sizeof(bm), &bm);
mSize.cx = bm.bmWidth; //nWidth;
mSize.cy = bm.bmHeight; //nHeight;
}
返回CBitmap位图对象和CSize表示大小，然后作为把返回得Bitmap作为普通位图那么操作就行，
只要你会怎么显示位图，就懂得怎么样显示这些图片了。

[gameboy999]

IPicture *pPic;
IStream *pStm;
CFileStatus fstatus;
CFile file;
LONG cb;
if (file.Open("c://test.jpg",CFile::modeRead)&&file.GetStatus("c://test.jpg",fstatus)&&((cb = fstatus.m_size) != -1))
{
HGLOBAL hGlobal = GlobalAlloc(GMEM_MOVEABLE, cb);
LPVOID pvData = NULL;
if (hGlobal != NULL)
{
if ((pvData = GlobalLock(hGlobal)) != NULL)
{
file.ReadHuge(pvData, cb);
GlobalUnlock(hGlobal);
CreateStreamOnHGlobal(hGlobal, TRUE, &pStm);
if(SUCCEEDED(OleLoadPicture(pStm,fstatus.m_size,TRUE,IID_IPicture,(LPVOID*)&pPic)))
{
OLE_XSIZE_HIMETRIC hmWidth;
OLE_YSIZE_HIMETRIC hmHeight;
pPic->get_Width(&hmWidth);
pPic->get_Height(&hmHeight);
double fX,fY;
//获得象素值
fX=(double)dc.GetDeviceCaps(HORZRES);//*(double)hmWidth/((double)dc.GetDeviceCaps(HORZSIZE)*100.0);
fY=(double)dc.GetDeviceCaps(VERTRES);//*(double)hmHeight/((double)dc.GetDeviceCaps(VERTSIZE)*100.0);
if(FAILED(pPic->Render(dc,0,0,(DWORD)fX,(DWORD)fY,0,hmHeight,hmWidth,-hmHeight,NULL)))
AfxMessageBox("Failed To Render The picture!");
pPic->Release();
}
else
AfxMessageBox("Error Loading Picture From Stream!");
}
}
}
else
AfxMessageBox("Can't Open Image File!");

[ferretzhu]

非常感谢

[GolemZ]

哇，神奇，原来还有个OleLoadPicture...

[tigal]

谢谢