Groups > comp.sys.apple2.programmer > #4557

Re: Retrieve hires pixel value

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From	Michael J. Mahon <mjmahon@aol.com>
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Michael Pohoreski <michael.pohoreski@gmail.com> wrote:
> If you don't want the flickering, and want something faster, it is rather
> trivial to piggy-back upon Applesoft's HPOSN @ $F411.  Any non zero
> values means the pixel is on.
> 
> Treating the screen as monochrome 280x192 image here is a demo program: HGR.PIXEL
> 
> 1 GOTO 10
> 2 X0=X:X1=X>255:IF X1 THEN X0=X-256
> 3 POKE 769,Y:POKE 771,X0:POKE 773,X1:CALL 768:P=PEEK(785)
> 4 PRINT "X=";X;" Y=";Y;" P=";P:GET A$:RETURN
> 10 FOR I=0 TO 16:READ B:POKE 768+I,B:NEXT
> 20 HGR
> 30 POKE  8192, 1:X=  0:Y=  0:GOSUB 2
> 40 POKE  8231,64:X=279:Y=  0:GOSUB 2
> 50 POKE 15824, 1:X=  0:Y=159:GOSUB 2
> 60 POKE 15863,64:X=279:Y=159:GOSUB 2 
> 99 DATA 169,0,162,0,160,0,32,17,244,177,38,37,48,141,17,3,96
> 
> 
> The corresponding Merlin HGR pixel test assembly and ML code @ $300:
> 
>                 ; === Applesoft ROM ===
>                 GBASL   EQU $26
>                 COLOR   EQU $30
>                 HPOSN   EQU $F411  ; A=row, X=low  byte column, Y=high byte column
> 
>                 ; Variables
>                 y       EQU 0
>                 x       EQU 279
>                 x0      EQU x&255
>                 x1      EQU x/256
> 
>                         ORG $300
> 300:A9 00               LDA #y
> 302:A2 17               LDX #x0
> 304:A0 01               LDY #x1
> 306:20 11 F4            JSR HPOSN
> 308:B1 26               LDA (GBASL),Y
> 30B:25 30               AND COLOR
> 30D:8D 11 03            STA Results
> 310:60                  RTS
> 311:00          Results DB 00
> 
> It's a pity Bill Gates couldn't shoe-horn this into Applesoft.  I guess
> he would rather waste bytes with an encrypted reverse "MICROSOFT!"
> signature at $F094 and unused HLINRL @ $F530. :-/
> i.e.
> http://www.txbobsc.com/scsc/scdocumentor/F49C.html
> http://www.txbobsc.com/scsc/scdocumentor/EFEA.html
> 
> Cheers
> Michael
> 
> 
> 

As I understand it, Bill Gates (or Microsoft) didn’t have anything to do
with the hi-res graphics extensions—that was Apple’s (mostly Woz’s)
contribution. 

-- 
-michael - NadaNet 3.1 and AppleCrate II:  http://michaeljmahon.com

Thread

Retrieve hires pixel value Zellyn <zellyn@gmail.com> - 2018-05-23 10:56 -0700
  Re: Retrieve hires pixel value D Finnigan <dog_cow@macgui.com> - 2018-05-23 18:41 +0000
  Re: Retrieve hires pixel value Michael J. Mahon <mjmahon@aol.com> - 2018-05-23 18:56 -0500
    Re: Retrieve hires pixel value Zellyn <zellyn@gmail.com> - 2018-05-23 20:52 -0700
    Re: Retrieve hires pixel value Michael Pohoreski <michael.pohoreski@gmail.com> - 2018-05-26 11:07 -0700
      Re: Retrieve hires pixel value Michael J. Mahon <mjmahon@aol.com> - 2018-05-26 16:53 -0500
        Re: Retrieve hires pixel value D Finnigan <dog_cow@macgui.com> - 2018-05-28 22:55 +0000
          Re: Retrieve hires pixel value Andy McFadden <thefadden@gmail.com> - 2018-05-29 07:59 -0700
            Re: Retrieve hires pixel value Antoine Vignau <antoine.vignau@laposte.net> - 2018-05-29 11:46 -0700
          Re: Retrieve hires pixel value Michael J. Mahon <mjmahon@aol.com> - 2018-05-29 10:47 -0500
          Re: Retrieve hires pixel value Antoine Vignau <antoine.vignau@laposte.net> - 2018-05-29 11:48 -0700
            Re: Retrieve hires pixel value D Finnigan <dog_cow@macgui.com> - 2018-05-29 19:46 +0000

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