一个屏幕捕捉的例子

void CPage1::WriteBmpToFile(HBITMAP hBitmap)
{
    HDC hDC =::CreateDC("DISPLAY",NULL,NULL,NULL);
    int iBits = ::GetDeviceCaps(hDC, BITSPIXEL) * ::GetDeviceCaps(hDC, PLANES);//当前分辨率下每个像素所占字节数 
    ::DeleteDC(hDC);

    WORD   wBitCount;   //位图中每个像素所占字节数   
    if (iBits <= 1)
  wBitCount = 1;
    else if (iBits <= 4)
  wBitCount = 4;
    else if (iBits <= 8)
  wBitCount = 8;
    else if (iBits <= 24)
  wBitCount = 24;
    else
  wBitCount = iBits;
     
 DWORD   dwPaletteSize=0; //调色板大小， 位图中像素字节大小
    if (wBitCount <= 8)  
  dwPaletteSize = (1 << wBitCount) * sizeof(RGBQUAD); 
 

 BITMAP  bm;        //位图属性结构
    ::GetObject(hBitmap, sizeof(bm), (LPSTR)&bm); 

   
 BITMAPINFOHEADER   bi;       //位图信息头结构    
 bi.biSize            = sizeof(BITMAPINFOHEADER); 
    bi.biWidth           = bm.bmWidth;
    bi.biHeight          = bm.bmHeight;
    bi.biPlanes          = 1;
    bi.biBitCount        = wBitCount;
    bi.biCompression     = BI_RGB; //BI_RGB表示位图没有压缩
    bi.biSizeImage       = 0;
    bi.biXPelsPerMeter   = 0;
    bi.biYPelsPerMeter   = 0;
    bi.biClrUsed         = 0;
    bi.biClrImportant    = 0;
 
    DWORD dwBmBitsSize = ((bm.bmWidth * wBitCount+31)/32) * 4 * bm.bmHeight;   
    HANDLE hDib  = ::GlobalAlloc(GHND,dwBmBitsSize + dwPaletteSize + sizeof(BITMAPINFOHEADER));  //为位图内容分配内存
    LPBITMAPINFOHEADER lpbi = (LPBITMAPINFOHEADER)GlobalLock(hDib);
    *lpbi = bi;
 
    HANDLE hPal = ::GetStockObject(DEFAULT_PALETTE);  // 处理调色板
 HANDLE  hOldPal=NULL;
    if (hPal)
    {
  hDC = ::GetDC(NULL);
  hOldPal = SelectPalette(hDC,(HPALETTE)hPal, FALSE);
  RealizePalette(hDC);
    }
    ::GetDIBits(hDC, hBitmap, 0, (UINT) bm.bmHeight,(LPSTR)lpbi + sizeof(BITMAPINFOHEADER)+dwPaletteSize,(BITMAPINFO*)lpbi,DIB_RGB_COLORS);// 获取该调色板下新的像素值
    if (hOldPal)//恢复调色板
    {
  SelectPalette(hDC, (HPALETTE)hOldPal, TRUE);
  RealizePalette(hDC);
  ::ReleaseDC(NULL, hDC);
    } 
  
 BITMAPFILEHEADER   bmfHdr; //位图文件头结构    
 bmfHdr.bfType = 0x4D42;  // "BM"   // 设置位图文件头
 DWORD dwDIBSize = sizeof(BITMAPFILEHEADER) + sizeof(BITMAPINFOHEADER) + dwPaletteSize + dwBmBitsSize; 
 bmfHdr.bfSize = dwDIBSize;
 bmfHdr.bfReserved1 = 0;
 bmfHdr.bfReserved2 = 0;
 bmfHdr.bfOffBits = (DWORD)sizeof(BITMAPFILEHEADER) + (DWORD)sizeof(BITMAPINFOHEADER) + dwPaletteSize;
 
 HANDLE hFile = CreateFile(m_strFilePath, GENERIC_WRITE, 0, NULL, CREATE_ALWAYS,FILE_ATTRIBUTE_NORMAL | FILE_FLAG_SEQUENTIAL_SCAN, NULL);//创建位图文件  
 DWORD dwWritten;
 WriteFile(hFile, (LPSTR)&bmfHdr, sizeof(BITMAPFILEHEADER), &dwWritten, NULL); // 写入位图文件头
 WriteFile(hFile, (LPSTR)lpbi, dwDIBSize, &dwWritten, NULL);// 写入位图文件其余内容
 
 GlobalUnlock(hDib);   //清除  
 GlobalFree(hDib);
 CloseHandle(hFile);  
 
}