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

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On Thursday, February 18, 2016 at 4:53:50 PM UTC-6, denisb...@gmail.com wrote:
> On Tuesday, 16 February 2016 14:39:28 UTC+11, gid...@sasktel.net  wrote:
> > bit #
> > 0 1 2 3 4 5 6 7   0 1 2 3 4 5 6 7
> > 
> >          color bit          color bit
> >               |                 |    
> > 0 0 0 0 0 0 0 0   0 0 0 0 0 0 0 0
> > |_| |_| |_| |_____| |_| |_| |_| 
> > 
> >  0   1   2     3     4   5   6
> > 
> 
> Is this to do with double hi-res, or something else I completely misunderstand? Because according to the Apple II reference manual every bit maps to a pixel and there is no concept of odd/even bytes.
> 
> In the scheme described above, which color bit controls pixel #3?

The original poster of the above and I were discussing single hi-res at the time, so I'd say it's safe to assume it has nothing to do with hi-res.

As to the bit/pixel mapping, here is how I learned it from several graphics books. I'm doing a lot of graphics programming right now and have found this model to be very accurate. 


COL# = column 

              BYTE 0                BYTE1
COL# 0 1 2 3 4 5 6       7 8 9 A B C D   
BIT#   0 1 2 3 4 5 6  7   0 1 2 3  4 5 6 7

This is an extract of bit map of the first two bytes in the upper left corner of the screen.

Bit #7 in byte0 controls the color for bits in byte0. Bit #7 in byte1 controls the color for bits in byte1

So for example you asked about pixel #3:

00010001

This binary would turn on pixel #3 and would turn on the color bit that affects it.

Regarding odd/even bytes. It is really odd/even columns that is the consideration. Blue/violet can only be drawn in even columns and green/orange can only be drawn in odd columns. There are a few quirks but I've found in practice this to be generally accurate. 

Also note how the first bit in the byte 0 is column #0 (an even numbered column) and how the first bit in byte 1 is column #7 (an odd column). This is because the color bits don't "count" for purposes of counting columns.

In this way, the layout of the odd/even columns follows a pattern that repeats every 2 bytes. This is relevant when drawing color, because in essence, which bits turn on the odd vs. even pixels are different depending on where on the screen the byte is mapped to. 

Converting the binary to a hex value to store in memory is a whole other topic, it's not a simple as calculating the hex equivalent of the binary number as written (happy to elaborate if that's of interest).  



Here are few graphics books I found very helpful. They are game focused, but the concepts are relevant for many graphics applications. They really break it all down.

Apple Graphics & Arcade Game Design (Jeffery Stanton)
Hi-Res Graphics and Animation Using Assembly Language (Leonard Malkin)

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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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