From: http://blog.csdn.net/boythl/article/details/3137446

今天在VC6中顯示JPG圖片，采用了內存DC緩存的方法刷新，但死活刷不出來，查了一下午才明白（沒辦法，很少用GDI，我小菜一個:( ）：使用IPicture::Render函數向DC上貼圖時，若DC是一個內存DC，一定要先SelectObject一個CBitmap，內存DC沒有Bitmap是畫不出來的！??

? 另外，IPicture是COM庫，需要注意初始化COM，

??CMYApp::InitInstance() 里使用 CoInitialize(NULL);

? CMYApp::ExitInstance() 里使用 CoUninitialize();

?

?? 下面貼出顯示JPG圖片到DC的函數，來自網上，自己整理了下，據說還可顯示GIF圖片的第一禎圖片，我未用到。

/*************************************************

Function????:?ShowJPG

Description?:?在DC上按圖片原始尺寸顯示JPG圖片

Calls???????:?

Called?By???:?

Parameter???:?[CDC*?pDC]?---?DC

????????????:?[CString?strPath]?---?要顯示的圖片路徑，建議全路徑

????????????:?[int?x]?---?DC上顯示的X位置?

????????????:?[int?y]?---?DC上顯示的Y位置

????????????:?[bool?OriginalSize]?---?是否按圖片原始尺寸顯示,false時將按DC大小縮放

Return??????:?bool?---?是否成功

Author??????:?Unknown

Date????????:?2008-10-24

Modify??????:?

*************************************************/

bool?ShowJPG(CDC*?pDC,CString?strPath,?int?x,?int?y,?bool?OriginalSize)

{????

????IStream?*pStm;?

????CFileStatus?fstatus;

????CFile?file;

????LONG?cb;?

????

????//打開文件并檢測文件的有效性???

????if?(file.Open(strPath,?CFile::modeRead)?&&?

????????file.GetStatus(strPath,fstatus)?&

????????((cb?=?fstatus.m_size)?!=?-1))?????

????{????????

????????HGLOBAL?hGlobal?=?GlobalAlloc(GMEM_MOVEABLE,?cb);????????

????????LPVOID?pvData?=?NULL;?????????

????????if?(hGlobal?!=?NULL)????????

????????{????????????

????????????pvData?=?GlobalLock(hGlobal);????????????

????????????if?(pvData?!=?NULL)???????????

????????????{???????????????

????????????????file.ReadHuge(pvData,?cb);??????

????????????????GlobalUnlock(hGlobal);???????????

????????????????CreateStreamOnHGlobal(hGlobal,?TRUE,?&pStm);?????

????????????}?????

????????}?

????}????

????else???

????{???????

????????return?false;??

????}

????//打開文件結束???

????

????//顯示JPEG圖片?

????IPicture?*pPic;????

????

????//load?image?from?file?stream???

????if(SUCCEEDED(OleLoadPicture(pStm,?fstatus.m_size,?TRUE,IID_IPicture,?(LPVOID*)&pPic)))???

????{????

????????if?(OriginalSize)?//圖片原始大小顯示

????????{

????????????long?nWidth?=?0,?nHeight?=?0;?//?寬高，MM_HIMETRIC?模式，單位是0.01毫米?

????????????pPic->get_Width(?&nWidth?);?//?寬?

????????????pPic->get_Height(?&nHeight?);?//?高?

????????????

????????????CSize?sz(?nWidth,?nHeight?);?

????????????pDC->HIMETRICtoDP(?&sz?);?//?轉換?MM_HIMETRIC?模式單位為?MM_TEXT?像素單位?

????????????pPic->Render(pDC->m_hDC,?0,?0,?sz.cx,?sz.cy,?

????????????????0,?nHeight,?nWidth,?-nHeight,?NULL);?

????????}???

????????else

????????{

????????????OLE_XSIZE_HIMETRIC?hmWidth;??????

????????????OLE_YSIZE_HIMETRIC?hmHeight;????

????????????pPic->get_Width(&hmWidth);

????????????pPic->get_Height(&hmHeight);???

????????????

????????????//get?image?height?and?width??

????????????double?fX,fY;

????????????fX?=?(double)pDC->GetDeviceCaps(HORZRES)??*?(double)hmWidth?/

????????????????((double)pDC->GetDeviceCaps(HORZSIZE)?*?100.0);?

????????????fY?=?(double)pDC->GetDeviceCaps(VERTRES)??*?(double)hmHeight?/

????????????????((double)pDC->GetDeviceCaps(VERTSIZE)?*?100.0);??

????????????

????????????//use?render?function?display?image????

????????????//按圖片原始大小顯示

????????????if(FAILED(pPic->Render(*pDC,x,y,(DWORD)fX,(DWORD)fY,0,hmHeight,hmWidth,-hmHeight,NULL)))?????????

????????????{

????????????????pPic->Release();??

????????????????return?false;????????

????????????}

????????}???????

????????

????????if?(?pStm?)?pStm->Release();?//?釋放?IStream?指針

????????if?(?pPic?)?pPic->Release();?//?釋放?IPicture?指針??

????}???

????else????

????{??????

????????return?false;???

????}????

????

????return?true;

}

?? 感謝vane小弟的幫助！及一個blog： http://topameng.spaces.live.com/blog/cns!f962d4854a8233d!248.entry ===================================

非注明轉載的文章和blog在未特殊聲明情況下一般為本人原創或整理，
原創文章版權歸沙漠孤狐（lonefox）所有；轉載文章版權歸原作者所有；

http://blog.csdn.net/boythl

歡迎轉載，但請注明出處，保留作者和版權信息。

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