Apple II resolution (was Apple IIe power questions)

["Roger Johnstone" <rojaws@es.co.nz>]

----------
In article <388A3B50.AE515FAE@dcnet2000.com>, Phoenyx <quazar@dcnet2000.com>
wrote:


>Jeff Blakeney wrote:
>> By the way, that brings up another nit pick.  :-)
>> 
>> Hi-res mode can actually display 560x192 in black and white but with
>> some limitations.  It has to do with the fact that plotting a white
>> dot only displays half a pixel.  HCOLOR=3 draws the dot of the left
>> half of the pixel and HCOLOR=7 draws the dot on the right half.  This
>> is a simplification of the method but it does exist.  :-)
>
>You know, this has been debated in the Apple2 arena ever since the
>computer was designed. Many people vehemently deny that the Apple can
>display more than 280 pixels, but I have seen software which proves
>differently. In fact, in the old Nibble there was a program which could
>draw very fine lines and circles based upon this.
>
>Which brings up the argument of how many colors can the Apple display
>in hi-res mode?
>
>Phoenyx

That program sounds like Hyper-Res Plus by Alvin Tutas, from the
May 1990 edition of Nibble. It adds new ampersand HPLOT and HCOLOR commands
to BASIC which use the colour half-pixel shift to double the hi-res screen
resolution to 560 pixels across. It works well on a monochrome monitor, but
this method has a draw back. If two lines cross through the same screen byte
(each 7 pixel group) then the half-shift may get changed. This is the same
effect that happens on a colour screen when you draw lines from the low and
high colour groups too close together.

I remember once seeing a game title screen which used the half-shift to very
good
effect. I'm sure it was Archon. The title screen was in black and white. If
you look
at the edges of the diagonals they are twice as smooth (or half as jagged)
as you would normally get. I liked the picture so much I printed it out, and
was very disappointed at how jagged it became. The printer dump program knew
nothing about the half-shift!


Roger Johnstone, Invercargill, New Zealand
http://homepages.ihug.co.nz/~rojaws
------------------------------------------
Programming today is a race between software engineers striving to build
bigger and better idiot-proof programs, and the Universe trying to produce
bigger and better idiots. So far, the Universe is winning. - Rich Cook