[nlist-mcc] Re: Recent WPAA implementation for OS3
- From: Ilkka Lehtoranta <ilkleht@xxxxxxxxxxx>
- To: NList-Mailingliste <nlist-mcc@xxxxxxxxxxxxx>
- Date: Fri, 22 Feb 2008 20:18:13 +0200 (EET)
On Wed, 20 Feb 2008, [ISO-8859-15] Thore Böckelmann wrote:
> Hi NList developers!
>
> itix recently supplied a custom WritePixelArrayAlpha() implementation for
> OS3. I
> think the idea is to provide alpha channel blitting for OS3 systems not
> running
> CGX or P96. So far so good. But the point is that one needs a
> picture.datatype
> being able to deliver proper alpha channel data at all. The picture.datatypes
> of
> OS4 and MOS do this by default, for OS3 AfAOS is necessary, especially its
> picture.datatype V46+.
>
> All in all, OS3 needs CGX V45+ and picture.datatype V46+ to handle alpha
> channel
> blitting itself. With just pic.dt V46+ and itix' WPAA() implementation
> (which
> should be renamed, to avoid confusion and compiler errors) alpha blitting
> should
> work even on plain AGA systems.
Custom WPAA() is included only in 68k builds. I dont know how it could
cause compiler errors. Confusion, possibly. Could be perhaps moved to
extrasrc.
On AGA you probably mean combining ARGB images and later remapping them to
CLUT format? Only problem there is that WPAA() requires
ReadPixelArray()/WritePixelArray()...
> Without pic.dt V46 all the work is senseless, since all older versions
> of picture.datatype will deliver a complete opaque alpha channel.
Hmm... I thought pic.dt on OS3 (with std CGX or P96 installation) returned
proper alpha channel with right datatypes. I remember Freeciv had PNG
graphics and it worked well once you had right datatypes installed. But
maybe they always returned only 0x00 or 0xff (transparency on/off) on
the alpha component. I havent used 68k system in six years.
Ilkka
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