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Re: Assembly Hi-Res Graphics, question about color patterns that seem to violate the "rules"

Newsgroups comp.sys.apple2.programmer
Subject Re: Assembly Hi-Res Graphics, question about color patterns that seem to violate the "rules"
From Michael J. Mahon <mjmahon@aol.com>
References <2b4d01aa-0679-404d-93a3-1813bc37e7ee@googlegroups.com> <1aa59295-b514-4d91-babf-3fb788e6cd15@googlegroups.com>
Message-ID <JYCdnRFWUq36mlXLnZ2dnUU7-RkAAAAA@giganews.com> (permalink)
Date 2016-02-20 00:27 -0600

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<denisbytezone@gmail.com> wrote:
> I've been trying to get the double byte method to work, and it mostly
> does work, but in some instances the resulting images look a bit off. So
> I was wondering if someone with a physical apple and a colour screen
> could try an experiment for me.
> 
> In the following description I have the bits ordered from most
> significant to least significant, which means the colour bit is on the
> left, and the pixels are interpreted in right-to-left order.
> 
> A byte with the value 0x06 converts to 0-0-0-0 0-1-1-0 in binary, which
> in my understanding means first pixel (column 0) equals 0 (black), the
> second pixel (column 1) equals 1 (green), the third pixel (column 2)
> equals 1 (violet) and the fourth pixel (column 3) equals 0 (black).
> However the two consecutive 1 bits (according to the apple manual)
> override the colours and become two consecutive white pixels.
> 
> So what actually appears on a physical apple? A green pixel followed by a
> violet pixel, or two white pixels? Because according to the double-byte
> method it should be two coloured pixels as they come from separate double-bytes.
> 
> For reference, I am using the Apple ][ Reference Manual 1979, pp 19.
> Please don't make me type in the entire section :)
> 

It's two white pixels. 

Two consecutive one bits produce *no* 3.58MHz frequency component, and
therefore no chroma signal. Since there two consecutive one bits produce
only one pulse, two pixels wide, there is only a two-pixel wide white
"dash", not two separate dots. 

Color in Apple II video is *entirely* a consequence of how an analog NTSC
monitor interprets the binary video bit stream. The luminance is determined
by the number of one bits in a "pixel group" (2 bits for HGR, 4 bits for
DHGR), the hue is determined by the phase of the 3.58MHz component of the
bit stream, and the saturation by the amplitude of the 3.58MHz component. 

There truly are no "colored pixels", only a monitor's interpretation of the
video bit stream as an analog composite video signal. If that signal
contains a color burst on the "back porch" of the horizontal blanking
pulse, the monitor will interpret any 3.58MHz frequency component in the
video as a chroma subcarrier and display colors. 

If it's what you intended, it's called color graphics, if not, it's called
"fringing" or "artifacts". ;-)

If you really want to understand, you need to study how NTSC video is
encoded/decoded, including the bandpass limitations on the luminance and
chrominance signals. Without that understanding, Apple II color just seems
"approximate" (which is good enough for pie charts, but insufficient for
subtle artistic effects. 

For example, the actual color displayed by an NTSC monitor depends on at
least 10-12 bits surrounding the "pixel". 
-- 
-michael - NadaNet 3.1 and AppleCrate II:  http://michaeljmahon.com

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Assembly Hi-Res Graphics, question about color patterns that seem to violate the "rules" Mark Lemmert <mark.lemmert@gmail.com> - 2016-02-15 11:40 -0800
  Re: Assembly Hi-Res Graphics, question about color patterns that seem to violate the "rules" gids.rs@sasktel.net - 2016-02-15 12:33 -0800
    Re: Assembly Hi-Res Graphics, question about color patterns that seem to violate the "rules" gids.rs@sasktel.net - 2016-02-15 12:38 -0800
      Re: Assembly Hi-Res Graphics, question about color patterns that seem to violate the "rules" Mark Lemmert <mark.lemmert@gmail.com> - 2016-02-15 14:11 -0800
        Re: Assembly Hi-Res Graphics, question about color patterns that seem to violate the "rules" dempson@actrix.gen.nz (David Empson) - 2016-02-16 14:22 +1300
          Re: Assembly Hi-Res Graphics, question about color patterns that seem to violate the "rules" Mark Lemmert <mark.lemmert@gmail.com> - 2016-02-15 18:33 -0800
    Re: Assembly Hi-Res Graphics, question about color patterns that seem to violate the "rules" Mark Lemmert <mark.lemmert@gmail.com> - 2016-02-15 14:08 -0800
      Re: Assembly Hi-Res Graphics, question about color patterns that seem to violate the "rules" gids.rs@sasktel.net - 2016-02-15 19:39 -0800
        Re: Assembly Hi-Res Graphics, question about color patterns that seem to violate the "rules" gids.rs@sasktel.net - 2016-02-15 19:47 -0800
          Re: Assembly Hi-Res Graphics, question about color patterns that seem to violate the "rules" David Schmidt <schmidtd@my-deja.com> - 2016-02-15 23:25 -0500
            Re: Assembly Hi-Res Graphics, question about color patterns that seem to violate the "rules" gids.rs@sasktel.net - 2016-02-16 08:42 -0800
        Re: Assembly Hi-Res Graphics, question about color patterns that seem to violate the "rules" Mark Lemmert <mark.lemmert@gmail.com> - 2016-02-16 11:28 -0800
        Re: Assembly Hi-Res Graphics, question about color patterns that seem to violate the "rules" denisbytezone@gmail.com - 2016-02-18 14:53 -0800
          Re: Assembly Hi-Res Graphics, question about color patterns that seem to violate the "rules" Mark Lemmert <mark.lemmert@gmail.com> - 2016-02-18 15:28 -0800
          Re: Assembly Hi-Res Graphics, question about color patterns that seem to violate the "rules" gids.rs@sasktel.net - 2016-02-18 15:31 -0800
            Re: Assembly Hi-Res Graphics, question about color patterns that seem to violate the "rules" denisbytezone@gmail.com - 2016-02-18 15:42 -0800
              Re: Assembly Hi-Res Graphics, question about color patterns that seem to violate the "rules" gids.rs@sasktel.net - 2016-02-18 15:52 -0800
                Re: Assembly Hi-Res Graphics, question about color patterns that seem to violate the "rules" gids.rs@sasktel.net - 2016-02-18 16:09 -0800
              Re: Assembly Hi-Res Graphics, question about color patterns that seem to violate the "rules" gids.rs@sasktel.net - 2016-02-18 16:42 -0800
              Re: Assembly Hi-Res Graphics, question about color patterns that seem to violate the "rules" Michael Pohoreski <michael.pohoreski@gmail.com> - 2016-02-22 11:01 -0800
          Re: Assembly Hi-Res Graphics, question about color patterns that seem to violate the "rules" dempson@actrix.gen.nz (David Empson) - 2016-02-19 12:47 +1300
          Re: Assembly Hi-Res Graphics, question about color patterns that seem to violate the "rules" gids.rs@sasktel.net - 2016-02-18 15:49 -0800
            Re: Assembly Hi-Res Graphics, question about color patterns that seem to violate the "rules" gids.rs@sasktel.net - 2016-02-18 16:02 -0800
  Re: Assembly Hi-Res Graphics, question about color patterns that seem to violate the "rules" Michael Pohoreski <michael.pohoreski@gmail.com> - 2016-02-16 11:34 -0800
    Re: Assembly Hi-Res Graphics, question about color patterns that seem to violate the "rules" Mark Lemmert <mark.lemmert@gmail.com> - 2016-02-16 12:00 -0800
      Re: Assembly Hi-Res Graphics, question about color patterns that seem to violate the "rules" Michael Pohoreski <michael.pohoreski@gmail.com> - 2016-02-16 13:47 -0800
  Re: Assembly Hi-Res Graphics, question about color patterns that seem to violate the "rules" Michael Pohoreski <michael.pohoreski@gmail.com> - 2016-02-16 13:41 -0800
    Re: Assembly Hi-Res Graphics, question about color patterns that seem to violate the "rules" Mark Lemmert <mark.lemmert@gmail.com> - 2016-02-16 19:02 -0800
    Re: Assembly Hi-Res Graphics, question about color patterns that seem to violate the "rules" Mark Lemmert <mark.lemmert@gmail.com> - 2016-02-17 18:09 -0800
      Re: Assembly Hi-Res Graphics, question about color patterns that seem to violate the "rules" marc.depeo@brbent.com - 2016-02-18 00:43 -0800
        Re: Assembly Hi-Res Graphics, question about color patterns that seem to violate the "rules" wssimms@gmail.com - 2016-02-18 01:48 -0800
          Re: Assembly Hi-Res Graphics, question about color patterns that seem to violate the "rules" AppleIIGSMarc <appleiigsmarc@gmail.com> - 2016-02-18 08:50 -0800
            Re: Assembly Hi-Res Graphics, question about color patterns that seem to violate the "rules" AppleIIGSMarc <appleiigsmarc@gmail.com> - 2016-02-18 10:45 -0800
              Re: Assembly Hi-Res Graphics, question about color patterns that seem to violate the "rules" Michael Pohoreski <michael.pohoreski@gmail.com> - 2016-02-18 20:24 -0800
                Re: Assembly Hi-Res Graphics, question about color patterns that seem to violate the "rules" wssimms@gmail.com - 2016-02-18 20:32 -0800
                Re: Assembly Hi-Res Graphics, question about color patterns that seem to violate the "rules" AppleIIGSMarc <appleiigsmarc@gmail.com> - 2016-02-18 21:05 -0800
            Re: Assembly Hi-Res Graphics, question about color patterns that seem to violate the "rules" gids.rs@sasktel.net - 2016-02-18 15:08 -0800
            Re: Assembly Hi-Res Graphics, question about color patterns that seem to violate the "rules" Mark Lemmert <mark.lemmert@gmail.com> - 2016-02-18 15:31 -0800
          Re: Assembly Hi-Res Graphics, question about color patterns that seem to violate the "rules" Michael Pohoreski <michael.pohoreski@gmail.com> - 2016-02-18 13:18 -0800
            Re: Assembly Hi-Res Graphics, question about color patterns that seem to violate the "rules" wssimms@gmail.com - 2016-02-18 18:15 -0800
          Re: Assembly Hi-Res Graphics, question about color patterns that seem to violate the "rules" Michael Pohoreski <michael.pohoreski@gmail.com> - 2016-03-01 11:58 -0800
  Re: Assembly Hi-Res Graphics, question about color patterns that seem to violate the "rules" Michael Pohoreski <michael.pohoreski@gmail.com> - 2016-02-16 14:05 -0800
    Re: Assembly Hi-Res Graphics, question about color patterns that seem to violate the "rules" Mark Lemmert <mark.lemmert@gmail.com> - 2016-02-16 19:12 -0800
      Re: Assembly Hi-Res Graphics, question about color patterns that seem to violate the "rules" "Michael J. Mahon" <mjmahon@aol.com> - 2016-02-17 15:22 -0800
        Re: Assembly Hi-Res Graphics, question about color patterns that seem to violate the "rules" Mark Lemmert <mark.lemmert@gmail.com> - 2016-02-17 16:14 -0800
  Re: Assembly Hi-Res Graphics, question about color patterns that seem to violate the "rules" denisbytezone@gmail.com - 2016-02-19 14:34 -0800
    Re: Assembly Hi-Res Graphics, question about color patterns that seem to violate the "rules" Mark Lemmert <mark.lemmert@gmail.com> - 2016-02-19 16:17 -0800
      Re: Assembly Hi-Res Graphics, question about color patterns that seem to violate the "rules" denisbytezone@gmail.com - 2016-02-19 19:19 -0800
        Re: Assembly Hi-Res Graphics, question about color patterns that seem to violate the "rules" Michael Pohoreski <michael.pohoreski@gmail.com> - 2016-02-19 22:25 -0800
          Re: Assembly Hi-Res Graphics, question about color patterns that seem to violate the "rules" denisbytezone@gmail.com - 2016-02-19 23:12 -0800
            Re: Assembly Hi-Res Graphics, question about color patterns that seem to violate the "rules" Michael Pohoreski <michael.pohoreski@gmail.com> - 2016-02-19 23:27 -0800
              Re: Assembly Hi-Res Graphics, question about color patterns that seem to violate the "rules" Michael Pohoreski <michael.pohoreski@gmail.com> - 2016-02-19 23:31 -0800
                Re: Assembly Hi-Res Graphics, question about color patterns that seem to violate the "rules" wssimms@gmail.com - 2016-02-20 04:02 -0800
                Re: Assembly Hi-Res Graphics, question about color patterns that seem to violate the "rules" Michael Pohoreski <michael.pohoreski@gmail.com> - 2016-02-20 11:40 -0800
                Re: Assembly Hi-Res Graphics, question about color patterns that seem to violate the "rules" Michael Pohoreski <michael.pohoreski@gmail.com> - 2016-02-20 11:48 -0800
        Re: Assembly Hi-Res Graphics, question about color patterns that seem to violate the "rules" Mark Lemmert <mark.lemmert@gmail.com> - 2016-02-20 08:10 -0800
          Re: Assembly Hi-Res Graphics, question about color patterns that seem to violate the "rules" denisbytezone@gmail.com - 2016-02-20 16:25 -0800
            Re: Assembly Hi-Res Graphics, question about color patterns that seem to violate the "rules" Michael Pohoreski <michael.pohoreski@gmail.com> - 2016-02-20 16:37 -0800
            Re: Assembly Hi-Res Graphics, question about color patterns that seem to violate the "rules" Mark Lemmert <mark.lemmert@gmail.com> - 2016-02-20 18:29 -0800
              Re: Assembly Hi-Res Graphics, question about color patterns that seem to violate the "rules" gids.rs@sasktel.net - 2016-02-20 20:00 -0800
                Re: Assembly Hi-Res Graphics, question about color patterns that seem to violate the "rules" Mark Lemmert <mark.lemmert@gmail.com> - 2016-02-20 20:53 -0800
                Re: Assembly Hi-Res Graphics, question about color patterns that seem to violate the "rules" gids.rs@sasktel.net - 2016-02-20 23:11 -0800
                Re: Assembly Hi-Res Graphics, question about color patterns that seem to violate the "rules" denisbytezone@gmail.com - 2016-02-21 00:23 -0800
                Re: Assembly Hi-Res Graphics, question about color patterns that seem to violate the "rules" wssimms@gmail.com - 2016-02-21 01:41 -0800
                Re: Assembly Hi-Res Graphics, question about color patterns that seem to violate the "rules" wssimms@gmail.com - 2016-02-21 01:43 -0800
                Re: Assembly Hi-Res Graphics, question about color patterns that seem to violate the "rules" denisbytezone@gmail.com - 2016-02-21 02:29 -0800
                Re: Assembly Hi-Res Graphics, question about color patterns that seem to violate the "rules" denisbytezone@gmail.com - 2016-02-21 02:40 -0800
                Re: Assembly Hi-Res Graphics, question about color patterns that seem to violate the "rules" wssimms@gmail.com - 2016-02-21 08:03 -0800
                Re: Assembly Hi-Res Graphics, question about color patterns that seem to violate the "rules" gids.rs@sasktel.net - 2016-02-21 09:55 -0800
                Re: Assembly Hi-Res Graphics, question about color patterns that seem to violate the "rules" gids.rs@sasktel.net - 2016-02-21 10:28 -0800
                Re: Assembly Hi-Res Graphics, question about color patterns that seem to violate the "rules" gids.rs@sasktel.net - 2016-02-21 14:42 -0800
                Re: Assembly Hi-Res Graphics, question about color patterns that seem to violate the "rules" Michael J. Mahon <mjmahon@aol.com> - 2016-02-22 14:13 -0600
                Re: Assembly Hi-Res Graphics, question about color patterns that seem to violate the "rules" Michael Pohoreski <michael.pohoreski@gmail.com> - 2016-02-21 20:49 -0800
                Re: Assembly Hi-Res Graphics, question about color patterns that seem to violate the "rules" anthonypaulo@gmail.com - 2017-06-22 17:19 -0700
                Re: Assembly Hi-Res Graphics, question about color patterns that seem to violate the "rules" Mark Lemmert <mark.lemmert@gmail.com> - 2017-06-22 18:05 -0700
                Re: Assembly Hi-Res Graphics, question about color patterns that seem to violate the "rules" awanderin <awanderin@gmail.com> - 2017-06-22 23:00 -0600
                Re: Assembly Hi-Res Graphics, question about color patterns that seem to violate the "rules" Michael J. Mahon <mjmahon@aol.com> - 2017-06-23 12:59 -0500
                Re: Assembly Hi-Res Graphics, question about color patterns that seem to violate the "rules" David Schmenk <dschmenk@gmail.com> - 2017-06-23 13:12 -0700
                Re: Assembly Hi-Res Graphics, question about color patterns that seem to violate the "rules" Michael Pohoreski <michael.pohoreski@gmail.com> - 2017-06-25 07:30 -0700
                Re: Assembly Hi-Res Graphics, question about color patterns that seem to violate the "rules" anthonypaulo@gmail.com - 2017-06-25 08:30 -0700
                Re: Assembly Hi-Res Graphics, question about color patterns that seem to violate the "rules" Michael J. Mahon <mjmahon@aol.com> - 2017-06-25 13:55 -0500
                Re: Assembly Hi-Res Graphics, question about color patterns that seem to violate the "rules" Charlie <charlieDOTd@verEYEzon.net> - 2017-06-23 11:26 -0400
                Re: Assembly Hi-Res Graphics, question about color patterns that seem to violate the "rules" Michael Pohoreski <michael.pohoreski@gmail.com> - 2017-06-25 07:45 -0700
                Re: Assembly Hi-Res Graphics, question about color patterns that seem to violate the "rules" anthonypaulo@gmail.com - 2017-06-25 08:33 -0700
                Re: Assembly Hi-Res Graphics, question about color patterns that seem to violate the "rules" anthonypaulo@gmail.com - 2017-06-25 08:38 -0700
                Re: Assembly Hi-Res Graphics, question about color patterns that seem to violate the "rules" David Schmenk <dschmenk@gmail.com> - 2017-06-25 12:07 -0700
                Re: Assembly Hi-Res Graphics, question about color patterns that seem to violate the "rules" anthonypaulo@gmail.com - 2017-06-25 16:29 -0700
    Re: Assembly Hi-Res Graphics, question about color patterns that seem to violate the "rules" Michael J. Mahon <mjmahon@aol.com> - 2016-02-20 00:27 -0600
      Re: Assembly Hi-Res Graphics, question about color patterns that seem to violate the "rules" denisbytezone@gmail.com - 2016-02-19 23:14 -0800
  Re: Assembly Hi-Res Graphics, question about color patterns that seem to violate the "rules" Michael Pohoreski <michael.pohoreski@gmail.com> - 2016-03-01 11:48 -0800
    Re: Assembly Hi-Res Graphics, question about color patterns that seem to violate the "rules" Michael J. Mahon <mjmahon@aol.com> - 2016-03-01 16:24 -0600
    Re: Assembly Hi-Res Graphics, question about color patterns that seem to violate the "rules" Mark Lemmert <mark.lemmert@gmail.com> - 2016-03-02 10:05 -0800
      Re: Assembly Hi-Res Graphics, question about color patterns that seem to violate the "rules" Michael Finger <mike.finger@gmail.com> - 2016-04-06 13:21 -0700
        Re: Assembly Hi-Res Graphics, question about color patterns that seem to violate the "rules" Michael Pohoreski <michael.pohoreski@gmail.com> - 2016-04-06 13:32 -0700
        Re: Assembly Hi-Res Graphics, question about color patterns that seem to violate the "rules" gids.rs@sasktel.net - 2016-04-06 15:15 -0700
          Re: Assembly Hi-Res Graphics, question about color patterns that seem to violate the "rules" Michael Pohoreski <michael.pohoreski@gmail.com> - 2017-06-25 06:17 -0700
            Re: Assembly Hi-Res Graphics, question about color patterns that seem to violate the "rules" gids.rs@sasktel.net - 2017-06-25 21:33 -0700
              Re: Assembly Hi-Res Graphics, question about color patterns that seem to violate the "rules" Michael Pohoreski <michael.pohoreski@gmail.com> - 2017-06-26 11:12 -0700

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