BITMAPINFOHEADER 中的biHeight 高度参数决定数据存储方向,一般情况 biHeight > 0
If biHeight is positive, the bitmap is a bottom-up DIB and its origin is the lower-left corner. If biHeight is negative, the bitmap is a top-down DIB and its origin is the upper-left corner.
biBitCount :Specifies the number of bits-per-pixel.