Re: A89: 5 level grayscale

To: <assembly-89@lists.ticalc.org>
Subject: Re: A89: 5 level grayscale
From: "Miles Raymond" <m_rayman@bigfoot.com>
Date: Wed, 24 Feb 1999 00:31:46 -0600
Delivered-To: assembly-89-outgoing@towerguard.unix.edu.sollentuna.se
Delivered-To: assembly-89@lists.ticalc.org
Reply-To: assembly-89@lists.ticalc.org


You have forgotten one key aspect of greyscale, and that is the time that
each plane is displayed.  The basic 4-level greyscale works like this:

Plane0    Plane1
(2/3)     (1/3)     [number of cycles out of 3]

0         0         White
0         1         Light Grey
1         0         Dark Grey
1         1         Black

In the 7-level greyscale system, I believe it is like this:

Plane0    Plane1    Plane2
(2/4)     (1/4)     (1/4)     [number of cycles out of 4]

0         0         0         White
0         0         1         Very Light Grey
0         1         0         Light Grey
0         1         1         Grey    \______These are the same
1         0         0         Grey    /
1         0         1         Dark Grey
1         1         0         Very Dark Grey
1         1         1         Black

011 and 100 are the same, because they both remain on the screen for the
same ammount of time (2 out of 4 cycles).  In an 8-level greyscale system,
it would look like this:

Plane0    Plane1    Plane2
(6/9)     (2/9)     (1/9)     [number of cycles out of 9]

0         0         0         White
0         0         1         Very Light Grey
0         1         0         Light Grey
0         1         1         Dark Light Grey
1         0         0         Light Dark Grey
1         0         1         Dark Grey
1         1         0         Very Dark Grey
1         1         1         Black

This would result in a major increase in flicker, due to the higher number
of cycles.  I believe that 7-level greyscale is the best solution to a level
of greyscale greater than 4 because of the small number of cycles (only 4)
compared to the number of cycles required for 8-level (9 cycles).  Any level
of greyscale between 4 and 7 (ie:5 and 6), will produce the same ammount of
flicker as 7-level greyscale does, because the number of cycles is the same.
I hope this clears any confusion about greyscale.

-Miles Raymond      EML: m_rayman@bigfoot.com
ICQ: 13217756       IRC: Killer2        AIM: MRayMan
http://www.bigfoot.com/~m_rayman/

-----Original Message-----
From: TGaArdvark@aol.com <TGaArdvark@aol.com>
To: assembly-89@lists.ticalc.org <assembly-89@lists.ticalc.org>
Date: Tuesday, February 23, 1999 10:02 PM
Subject: Re: A89: 5 level grayscale


>> 5 level would be kinda dumb.  it's just a waste of a bit.  with 4 level,
you
>>  have 2 bits coding for 4 different shades.  if you up that to just 3
bits (
>> one
>>  bit more), you get 7 levels.  finding an intermediate would either mean
>>  sharing bits or wasting bits.  sorry if it's a "bit" confusing.  hahaha.
i
>>  kill myself.
>
>No, 3 bits is 8 levels.
>000  White
>001  Very light gray
>010  Light gray
>011  Medium light gray
>100  Medium dark gray
>101  Dark gray
>110  Very dark gray
>111  Black