Re: [Plib-devel] Texture loading problems (bmp/rgb)

[Jan R. <slo...@gm...>]

Am Sat, 18 Nov 2006 09:08:35 -0600 schrieb steve <sjb...@ai...>:

> Yes - that's it exactly.  There is an 'upside down' flag.  This
> is a typically stupid Microsoftian coding stupidity.   It makes
> it very fractionally easier for some programs to write out images
> if they store them that way up internally - at the price of
> belabouring every single image reading program with the additional
> code to conditionally flip them back the right way around.

> Worse still, the BMP file format is a horrible mess with
> multiple headers inside other headers - each of which can have
> duplicates of that flag bit.  Some programs set all of the
> flag bits - others set only one of them - some seem to treat
> the bit as applying consecutively so two 'invert' flags are
> supposed to flip it back the right way up.

Steve,

I found some more detailed information on the .bmp (DIB) format on
MSDN:

http://msdn2.microsoft.com/en-us/library/ms532290.aspx

But I didn't find any information about nested headers with duplicate
"upside down" flags. I only found this:

"biHeight
Specifies the height of the bitmap, in pixels. 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."

The biHeight field can only appear once in a bmp file, so it
shouldn't be a problem to get the orientation right. I think I'll
prepare a patch, but I guess this will breakt 3ds loading until
we also remove the forced bmp texture flipping there...

Kind regards,
Jan R.

-- 
Jan Reucker
email: jan dot reucker at web dot de
web:   http://www.reucker-online.de