Re: DHGR Color Question

[mjmahon@aol.com (Michael J. Mahon)]

Bryan Parkoff wrote:

>    I always use Aux Bank first.  Take a look.
>
>    1/2000: 7F 7F
>    0/2000: 11
>
>    First $7F displays 7 white pixels.
>    Second $11 displays 1st - white, 2nd - yellow, 3rd - orange, and
>4th-7th - DeepRed
>    Third $7F displays 7 white pixels.
>
>    If I change from white to deep red, take a look below.
>
>    1/2000: 08 22
>    0/2000: 11
>
>    First $08 displays 7 deep red pixels.
>    Second $11 displays 7 deep red pixels.
>    Third $22 displays 7 deep red pixels.
>
>    Please explain why second 7 pixels do not have solid deep red between
>white pixels.  Why first pixel is white, second pixel is yellow, third pixel
>is orange, and then fourth-seventh pixels are red.  Study 128 x 16 matrix
>and you can see randomized colors.

Bryan, I'm not willing to do the detailed research required to set
you straight here--_you_ should do it.  Then you will have a much
better understanding of what's going on.  (That, by the way, is what
Kent meant when he said that a careful reading of the source of
KEGS would answer many of your questions--KEGS is a software
implementation of an Apple IIgs, including DHGR mode.)

Some things to keep in mind:

1) The bits are shifted out LSB-first, so you have to account for that.

2) The DHGR color interpretation is not based on individual bits, but
on groups of 4 sequential bits.  It is intended to be displayed on an
NTSC color monitor and anything else will be an approximation--
including RGB.

3) the table you have shown does not have the bits positioned
correctly according to 1) above.  I think you'll find that that fixes
the problem.

The way to learn about these things is to try something and see
if it does what you expect.  If it doesn't (as in this case), try other
things and other ways of understanding what it _does_ do until
you figure it out.  Only by doing additional experiments until you
have clarified the situation will you learn what is actually going on.
(_Not_ by asking someone else as soon as an experiment does
something you don't expect.)

If you assume that the hardware is working perfectly, and it is
your understanding that is deficient, then you will learn quickly.

If, whenever an experiment produces an unexpected result, you
assume that the hardware is working improperly, then you will
learn nothing.

Try this approach and see if it doesn't yield dividends.  ;-)

-michael

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