win32 bitmap erroneously converted to monochrome - c++

Question

I'm trying to get the bits of a window icon, in order to send them through a socket. To test if I'm hable to get the BITMAP corresponding to the HICON, I save it on a file.
The problem is that, opening the file where I've saved the bitmap, it appear monochrome (black and white, not grey scale).
Here is the BITMAPINFO struct:
info.biSize = sizeof(BITMAPINFOHEADER);
info.biWidth = bitmap.bmWidth;
info.biHeight = bitmap.bmHeight;
info.biPlanes = 1;
info.biBitCount = 32;
info.biCompression = BI_RGB;
info.biSizeImage = 0;
info.biXPelsPerMeter = 0;
info.biYPelsPerMeter = 0;
info.biClrUsed = 0;
info.biClrImportant = 0;
And I compute the size of the bitmap as:
DWORD dwBmpSize2 = ((bitmap.bmWidth * bi.biBitCount + 31) / 32) * 4 * bitmap.bmHeight;
Then:
// Starting with 32-bit Windows, GlobalAlloc and LocalAlloc are implemented as wrapper functions that
// call HeapAlloc using a handle to the process's default heap. Therefore, GlobalAlloc and LocalAlloc
// have greater overhead than HeapAlloc.
HANDLE hDIB = GlobalAlloc(GHND, dwBmpSize);
char *lpbitmap = (char *)GlobalLock(hDIB);
//Prendo i bit dell'icona
HDC hdc = GetDC(hwnd);
GetDIBits(hdc, hbit, 0, (UINT)bitmap.bmHeight, lpbitmap, (BITMAPINFO*)&bi,DIB_RGB_COLORS);
wcout « "lpbitmap buffer: "« lpbitmap « endl;
// A file is created, this is where we will save the screen capture.
HANDLE hFile = CreateFile(L"captureqwsx.bmp",
GENERIC_WRITE,
0,
NULL,
CREATE_ALWAYS,
FILE_ATTRIBUTE_NORMAL, NULL);
// Add the size of the headers to the size of the bitmap to get the total file size
DWORD dwSizeofDIB = dwBmpSize + sizeof(BITMAPFILEHEADER) + sizeof(BITMAPINFOHEADER);
//Offset to where the actual bitmap bits start.
bmfHeader.bfOffBits = (DWORD)sizeof(BITMAPFILEHEADER) + (DWORD)sizeof(BITMAPINFOHEADER);
//Size of the file
bmfHeader.bfSize = dwSizeofDIB;
//bfType must always be BM for Bitmaps
bmfHeader.bfType = 0x4D42; //BM
DWORD dwBytesWritten = 0;
WriteFile(hFile, (LPSTR)&bmfHeader, sizeof(BITMAPFILEHEADER), &dwBytesWritten, NULL);
WriteFile(hFile, (LPSTR)&bi, sizeof(BITMAPINFOHEADER), &dwBytesWritten, NULL);
WriteFile(hFile, (LPSTR)lpbitmap, dwBmpSize, &dwBytesWritten, NULL);