Why I get a black screen while capturing screen?
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I want to use the follow codes to capture screen ,but I get a black screen. Please help me to find the errors! thanks! HWND hDesktopWnd=::GetDesktopWindow(); HDC hDesktopDC=::GetDC(hDesktopWnd); HDC hDesktopCompatibleDC=CreateCompatibleDC(hDesktopDC); HBITMAP hDesktopCompatibleBitmap=CreateCompatibleBitmap(hDesktopDC,GetSystemMetrics(SM_CXSCREEN),GetSystemMetrics(SM_CYSCREEN)); SelectObject(hDesktopCompatibleDC,hDesktopCompatibleBitmap); BitBlt(hDesktopCompatibleDC,0,0,GetSystemMetrics(SM_CXSCREEN) ,GetSystemMetrics(SM_CYSCREEN) ,hDesktopDC,0,0,SRCCOPY); // InvalidateRect(NULL,false); HDC hBmpFileDC=CreateCompatibleDC(hDesktopCompatibleDC); HBITMAP hBmpFileBitmap=CreateDIBSection(hDesktopCompatibleDC,&bi,DIB_RGB_COLORS,&pBits,NULL,0); SelectObject(hBmpFileDC,hBmpFileBitmap); BitBlt(hBmpFileDC,0,0,width,height,hDesktopCompatibleDC,0,0,SRCCOPY); // the fellow codes is save the bitmap HANDLE hFile=CreateFile((unsigned short *)szFileName,GENERIC_WRITE,FILE_SHARE_WRITE,NULL,CREATE_ALWAYS,FILE_ATTRIBUTE_NORMAL,NULL); bi.bmiHeader.biBitCount=16; // bi.bmiHeader.biClrUsed=0; bi.bmiHeader.biHeight=GetSystemMetrics(SM_CYSCREEN); //GetHeight(); bi.bmiHeader.biWidth=GetSystemMetrics(SM_CXSCREEN); //GetWidth(); bi.bmiHeader.biSize=sizeof(BITMAPINFOHEADER); bi.bmiHeader.biPlanes=1; bi.bmiHeader.biCompression=BI_RGB; // bi.bmiHeader.biXPelsPerMeter=0; // bi.bmiHeader.biYPelsPerMeter=0; // bi.bmiHeader.biClrImportant=0; DWORD bitSize=((bi.bmiHeader.biWidth*16)/8)*bi.bmiHeader.biHeight; bi.bmiHeader.biSizeImage=bitSize; bitHeader.bfType=((WORD)('M'<<8)|'B'); bitHeader.bfReserved1=0; bitHeader.bfReserved2=0; bitHeader.bfOffBits=(DWORD)(sizeof(BITMAPFILEHEADER)+bi.bmiHeader.biSize); bitHeader.bfSize=bi.bmiHeader.biSizeImage+bitHeader.bfOffBits; if(hFile!=INVALID_HANDLE_VALUE) { DWORD dwRet=0; WriteFile(hFile,&bitHeader,sizeof(bitHeader),&dwRet,NULL); WriteFile(hFile,&bi.bmiHeader,sizeof(bi.bmiHeader),&dwRet,NULL); WriteFile(hFile,pBits,bi.bmiHeader.biSizeImage,&dwRet,NULL); CloseHandle(hFile); } DeleteDC(hBmpFileDC); DeleteDC(hDesktopCompatibleDC); ::ReleaseDC(hDesktopWnd,hDesktopDC); DeleteObject(hBmpFileBitmap); DeleteObject(hDesktopCompatibleBitmap);
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I want to use the follow codes to capture screen ,but I get a black screen. Please help me to find the errors! thanks! HWND hDesktopWnd=::GetDesktopWindow(); HDC hDesktopDC=::GetDC(hDesktopWnd); HDC hDesktopCompatibleDC=CreateCompatibleDC(hDesktopDC); HBITMAP hDesktopCompatibleBitmap=CreateCompatibleBitmap(hDesktopDC,GetSystemMetrics(SM_CXSCREEN),GetSystemMetrics(SM_CYSCREEN)); SelectObject(hDesktopCompatibleDC,hDesktopCompatibleBitmap); BitBlt(hDesktopCompatibleDC,0,0,GetSystemMetrics(SM_CXSCREEN) ,GetSystemMetrics(SM_CYSCREEN) ,hDesktopDC,0,0,SRCCOPY); // InvalidateRect(NULL,false); HDC hBmpFileDC=CreateCompatibleDC(hDesktopCompatibleDC); HBITMAP hBmpFileBitmap=CreateDIBSection(hDesktopCompatibleDC,&bi,DIB_RGB_COLORS,&pBits,NULL,0); SelectObject(hBmpFileDC,hBmpFileBitmap); BitBlt(hBmpFileDC,0,0,width,height,hDesktopCompatibleDC,0,0,SRCCOPY); // the fellow codes is save the bitmap HANDLE hFile=CreateFile((unsigned short *)szFileName,GENERIC_WRITE,FILE_SHARE_WRITE,NULL,CREATE_ALWAYS,FILE_ATTRIBUTE_NORMAL,NULL); bi.bmiHeader.biBitCount=16; // bi.bmiHeader.biClrUsed=0; bi.bmiHeader.biHeight=GetSystemMetrics(SM_CYSCREEN); //GetHeight(); bi.bmiHeader.biWidth=GetSystemMetrics(SM_CXSCREEN); //GetWidth(); bi.bmiHeader.biSize=sizeof(BITMAPINFOHEADER); bi.bmiHeader.biPlanes=1; bi.bmiHeader.biCompression=BI_RGB; // bi.bmiHeader.biXPelsPerMeter=0; // bi.bmiHeader.biYPelsPerMeter=0; // bi.bmiHeader.biClrImportant=0; DWORD bitSize=((bi.bmiHeader.biWidth*16)/8)*bi.bmiHeader.biHeight; bi.bmiHeader.biSizeImage=bitSize; bitHeader.bfType=((WORD)('M'<<8)|'B'); bitHeader.bfReserved1=0; bitHeader.bfReserved2=0; bitHeader.bfOffBits=(DWORD)(sizeof(BITMAPFILEHEADER)+bi.bmiHeader.biSize); bitHeader.bfSize=bi.bmiHeader.biSizeImage+bitHeader.bfOffBits; if(hFile!=INVALID_HANDLE_VALUE) { DWORD dwRet=0; WriteFile(hFile,&bitHeader,sizeof(bitHeader),&dwRet,NULL); WriteFile(hFile,&bi.bmiHeader,sizeof(bi.bmiHeader),&dwRet,NULL); WriteFile(hFile,pBits,bi.bmiHeader.biSizeImage,&dwRet,NULL); CloseHandle(hFile); } DeleteDC(hBmpFileDC); DeleteDC(hDesktopCompatibleDC); ::ReleaseDC(hDesktopWnd,hDesktopDC); DeleteObject(hBmpFileBitmap); DeleteObject(hDesktopCompatibleBitmap);