Bitmap biHeight Negative or Positive?

[lily311]

As I observed, most bitmaps are bottom-up DIB and the biHeight
of BITMAPINFOHEADER are positive. After scanned a bitmap,
I have to save the RGB data in a top-down way because of time issue.
So I set the biHeight negative. If I double-click the bmp file
directly, it can be shown correctly, but can't load it with ::LoadImage();
If I change biHeight to positive, I can load it with ::LoadImage(),
but the bitmap is upside-down.

Any help be appreciated.