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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