轉自：https://www.douban.com/note/181738144/
3. ipicture
IPicture的縮放效果好一點，有兩種方法：1）一種是直接顯示不下載圖片到本地，[cpp] view plain copy
HRESULT CListListBox::ShowPic(CDC* pDC,CString strImgUrl,CRect rect) { HDC hDC_Temp = pDC->GetSafeHdc(); IPicture *pPic; IStream *pStm; HRESULT bResult;// = FALSE; DHRESULT CListListBox::ShowPic(CDC* pDC,CString strImgUrl,CRect rect) { HDC hDC_Temp = pDC->GetSafeHdc(); HRESULT bResult;// = FALSE; DWORD dwFileSize = 0,dwByteRead; CString url = strImgUrl; CString path = GetPic(strImgUrl); //if(url.Find(L".jpeg") != -1) return E_FAIL; if(path.IsEmpty()) { url = SavePic(url); //return FALSE; } else { url = path; } CFile file; if (!file.Open(url, CFile::modeRead|CFile::shareDenyWrite)) { return FALSE; } CArchive ar(&file, CArchive::load | CArchive::bNoFlushOnDelete); CArchiveStream arcstream(&ar); IPicture *pPic; IStream *pStm = (IStream*)&arcstream ; //HRESULT hr = OleLoadPicture(pStm, 0, FALSE,IID_IPicture, (LPVOID*)&pPic); //ASSERT(SUCCEEDED(hr) && m_spIPicture); //bResult=OleLoadPicture(pStm,dwFileSize,TRUE,IID_IPicture,(LPVOID*)&pPic); bResult=OleLoadPicture(pStm,0,FALSE,IID_IPicture,(LPVOID*)&pPic); if(FAILED(bResult)) return E_FAIL; OLE_XSIZE_HIMETRIC hmWidth; //圖片的真實寬度, 單位為英寸 OLE_YSIZE_HIMETRIC hmHeight; //圖片的真實高度, 單位為英寸 pPic->get_Width(&hmWidth); pPic->get_Height(&hmHeight); //轉換hmWidth和hmHeight為pixels距離，1英寸=25.4毫米 int nWidth = MulDiv(hmWidth,GetDeviceCaps(hDC_Temp,LOGPIXELSX),2540); int nHeight = MulDiv(hmHeight,GetDeviceCaps(hDC_Temp,LOGPIXELSY),2540); //縮放圖片 double nWZoom = nWidth / rect.Width(); double nHZoom = nHeight / rect.Height(); double nZoom = 1; nZoom = ( nWZoom > nHZoom ) ? nWZoom : nHZoom; nWidth /= nZoom; nHeight /= nZoom; int midW = (rect.left + rect.right) / 2; int midH = (rect.top + rect.bottom) / 2; CRect showRect(rect); showRect.left = ((midW - nWidth / 2) < rect.left) ? rect.left : (midW - nWidth / 2); showRect.right = ((midW + nWidth / 2) > rect.right) ? rect.right : (midW + nWidth / 2); showRect.top = ((midH - nHeight / 2) < rect.top) ? rect.top : (midH - nHeight / 2); showRect.bottom = ((midH + nHeight / 2) > rect.bottom) ? rect.bottom : (midH + nHeight / 2); if(showRect.left < 0 || showRect.right < 0 || showRect.top < 0 || showRect.bottom < 0) return E_FAIL; //將圖形輸出到屏幕上（有點像BitBlt） bResult=pPic->Render(hDC_Temp,showRect.left,showRect.top,showRect.Width(),showRect.Height(), 0,hmHeight,hmWidth,-hmHeight,NULL); pPic->Release(); file.Close();//關閉打開的文件 ar.Close(); arcstream.Release(); if (SUCCEEDED(bResult)) { return S_OK; } else { return E_FAIL; } } 把網絡圖片下載到本地還有一個小插曲，開始我使用File Open的方式讀取網絡圖片，對于有些圖片是管用的。但是GetLength得到的值有時會很小，直接導致圖片下載不全，OleLoadPicture的時候程序直接卡死了。[cpp] view plain copy CString CListListBox::SavePic(CString strImgUrl) { //本地緩存路徑 if(path.IsEmpty()) return L""; DWORD dwFileSize,dwByteRead; //讀取網頁上圖片文件，實際是個CHttpFile指針 CInternetSession session(L"HttpClient"); CStdioFile* httpFile = session.OpenURL(strImgUrl); if (httpFile!=INVALID_HANDLE_VALUE) { for(int i = 0; i < 100; i++) { dwFileSize = httpFile->GetLength();//獲取文件字節數 } if (dwFileSize==0xFFFFFFFF) { DWORD err = GetLastError(); return L""; } } else { return L""; } CFile file; if(file.Open(path,CFile::modeCreate|CFile::modeWrite)) { while(dwFileSize > 0) { BYTE* pvData = new BYTE[dwFileSize];//[100*1024*1024]; memset(pvData, 0, dwFileSize); dwByteRead = httpFile->Read(pvData,dwFileSize); file.Write(pvData,dwByteRead); delete pvData; dwFileSize -= dwByteRead; } } file.Close(); httpFile->Close(); session.Close(); return path; } 后來在網上搜了牛人寫的程序直接拿來用，居然很好用，速度也挺快[cpp] view%20plain copy CString CListListBox::SavePic(CString strImgUrl) { DWORD length=0; BYTE buffer[1024]; memset(buffer,0,1024); HINTERNET hInternet; hInternet=InternetOpen(_T("Testing"),INTERNET_OPEN_TYPE_PRECONFIG,NULL,NULL,0); if (hInternet==NULL) { //cout<<_T("Internet open failed!")<<endl; return L""; } HINTERNET hUrl; hUrl=InternetOpenUrl(hInternet,strImgUrl,NULL,0,INTERNET_FLAG_RELOAD,0); if (hUrl==NULL) { // cout<<_T("Internet open url failed!")<<endl; InternetCloseHandle(hInternet); return L""; } BOOL hwrite; DWORD written; HANDLE hFile; CString path = CreateLocalPath(strImgUrl); hFile=CreateFile(path,GENERIC_WRITE,0,0,CREATE_ALWAYS,FILE_ATTRIBUTE_NORMAL,0); if (hFile==INVALID_HANDLE_VALUE) { //cout<<_T("Create File failed!")<<endl; InternetCloseHandle(hUrl); InternetCloseHandle(hInternet); return L""; } BOOL read; while(1) { read=InternetReadFile(hUrl,buffer,sizeof(buffer),&length); if(length==0) break; hwrite=WriteFile(hFile,buffer,sizeof(buffer),&written,NULL); if (hwrite==0) { //cout<<_T("Write to file failed!")<<endl; CloseHandle(hFile); InternetCloseHandle(hUrl); InternetCloseHandle(hInternet); return L""; } } CloseHandle(hFile); InternetCloseHandle(hUrl); InternetCloseHandle(hInternet); return path; } 大功告成，由于開發時間匆忙，很多細節沒有追究，等以后有時間了再補上，這里做個記錄吧。新聞熱點
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