Each bitmap row is aligned to a word (16 bit) boundary.
It's easy to check - use Insider to open small icon for any app - the
rowBytes will be 0x0002
for 1 bpp bitmap.
Regards
Bozidar
> Hi Pete,
> Thanks for your reply, but I don't quite understand the calculation.
> I realise that the 8bpp played some part in the calculation, but in your
> WIDTHBYES macro, what does the "L" refer to? Would I be able to use that
> calculation for both 1bpp and 8bpp?
> How does it work out that for a 75 pixel wide bitmap, rowBytes is 10 for
> 1bpp, and 76 for 8bpp?
> Thanks,
> Trung
>
>
>
> From: GreatOwlS
> Date: Tue, 13 Jun 2000 10:35:15
>
> Each bitmap row is probably aligned to a 32-bit boundary (don't know for
> sure
> as I've never looked into it, but its not unreasonable). Your
> results are
> consistent with bitmap depths at various bits-per-pixel (in your
> case, 1bpp
> when < OS3.5 and 8bpp when OS3.5).
>
> The calculation for rowsize that you should be using is something like
>
> //Calculate DWORD-aligned bytecount based on a bitcount.
> #define WIDTHBYTES(bits) (((bits) + 31L) / 32L * 4)
>
> //Calculate DWORD-aligned bytecount based on pixel count and bitcount per
> pixel.
> #define ROWBYTES(cx, bpp) WIDTHBYTES(cx * bpp)
>
>
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