The best way to do transparancies is with masking.
I don't know if the PalmOS supports masking, so you'd
probably have to implement it yourself.
The basic idea is that you create two bitmaps, one
with your image and the other with a mask designating
which parts of the final image should come from your
bitmap and which parts should come from the background
that you are drawing it onto.
If I remember correctly, the equation for masking,
assuming monochrome background & bitmap, looks something
like this:
*pFinal = (*pBitmap && *pMask) | (*pBackground && ~(*pMask));
(This, of course, ignores the finer points of positioning
bitmaps at anywhere other than byte boundries on the
target screen, etc.)
--
-Richard M. Hartman
[EMAIL PROTECTED]
186,000 mi./sec ... not just a good idea, it's the LAW!
> -----Original Message-----
> From: David Korus [mailto:[EMAIL PROTECTED]]
> Sent: Thursday, November 18, 1999 12:35 PM
> To: '[EMAIL PROTECTED]'
> Subject: the BitBlt OR transparent bitmaps
>
>
> Hi all,
> I'm trying to do some graphics for a game, mainly trying to draw
> bitmaps with transparency. First of all, is there a function
> somewhere that
> can draw bitmaps with transparency? Say for example not
> overwriting any
> white pixels.
>
> Our other alternative is to use a BitBlt from the bitmap to the
> screen memory. Do any of you know of any BitBlt or RasterOps
> type code that
> I could use? I looked in the palm docs as well as the 6800 docs and
> couldn't find any functions that could do a BitBlt for me.
> There are plenty
> of mem-copy type operations, but I can't find any that work
> on non-byte
> aligned memory.
>
> It really seems like someone must have written some code to work
> with transparency before. I'm really not looking forward to
> writing my own
> BitBlt function...
>
>
> David Korus
>
