[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 <><
>
>
Interresting... do you have any source code examples of this? (too lazy to
find marspatrol =D)
- - Joe

--------------------------------
Joe Pemberton
http://tiworld.calc.org
--------------------------------


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