[A83] Re: greyscale
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[A83] Re: greyscale
> Van: Olle Hedman <alh@home.se>
>
> At 20:46 2001-12-20, you wrote:
> >It's different lcd drivers. We've talked about this before, but this is
> >the basic idea:
> >the 89 has a method that tells the driver that it is time to update
> >on the 83, the driver is independent of the calc(and this varies
> >depending on how new the batteries are).
> >
> >Thats why the 89 has 7 scale grey scale and we only have 2 colors :P
>
> Yes.
> But suckers idea is still right. On the 89 for 4 level gray you basicly
> have two buffers for the screen contents, and on an interrupt, you
> switch between the two. 2/3 of the time it displays one buffer, 1/3
> of the time the other.
> (there is other switching schemes but this is the most simple)
> The 89 lcd driver has a port where you set from which adress in
> memory to read the screen contents.
Nice grayscale on the Ti82/83(+) is also possible. The thing that can be
improved upon former approaches is that you don't write the entier buffer
to the screen at once. Do a some bit-masking between the buffers and you
get nice 4-level grayscale. 8-level is also possible that way, but then you
already see the bitmasking...
Basicaly you add interlace to the picture. On CRT monitors this is good for
bad headaches. But since the pixels of an LCD are much slower than one on
your CRT, the pixels get a gray'ish look. It's much like the grayscale used
in Marspatrol on the Ti83.
A drawback is that for a fast routine you need to use the graph-buffers
'the other way around' (byte order is different). Which means you need to
write new sprite routines.
Henk Poley <><