Re: A83: Re: Check this Pixel Routine. =)
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Re: A83: Re: Check this Pixel Routine. =)
Just wanted to let you know that ld a,(hl) should have been a ld (hl),a...
Joe Wingbermuehle
http://www.usmo.com/~joewing/
----- Original Message -----
From: Joe Wingbermuehle <joewing@usmo.com>
To: <assembly-83@lists.ticalc.org>
Sent: Saturday, December 19, 1998 8:09 PM
Subject: Re: A83: Re: Check this Pixel Routine. =)
>
>Just insert the cpl and leave the and (hl) as well. I'll show you why:
>let's say that the byte on the screen ( (hl) after running getPixel) is
>%00101111 and you want to change bit 3 (the output from getPixel is
>%00001000). This is what will happen:
> call getPixel ; (hl)=%00101111 | a=%00001000
> cpl ; (hl)=%00101111 | a=%11110111
> and (hl) ; (hl)=%00101111 | a=%00100111
> ld a,(hl) ; (hl)=%00100111
>So what basically happened was we turned off bit 3 of (hl).
>
>Joe Wingbermuehle
>http://www.usmo.com/~joewing/
>
>----- Original Message -----
>From: <Jkhum98@aol.com>
>To: <assembly-83@lists.ticalc.org>
>Sent: Saturday, December 19, 1998 7:57 PM
>Subject: Re: A83: Re: Check this Pixel Routine. =)
>
>
>>
>>Hey Joe (or anybody else who may have some time to) could you elaborate on
>>that change a little more...? All I should do is _Insert_ the "CPL"
>command,
>>but also leave the "AND (hl)" ? The function I want to take place is that
>the
>>specific Bit will become Cleared no matter what the original byte
>contained,
>>but not Every bit in that byte. Will that "AND (hl)" operation do this for
>me
>>along with the CPL? Thanks for the correction though. =)
>> --Jason K.
>>
>>In a message dated 12/19/98 8:04:15 PM, joewing@usmo.com writes:
>>
>>>Just a minor change, everything else looks like it should work though.
>>>Sorry about not responding sooner, I just don't much time lately.
>>>
>>>Joe Wingbermuehle
>>>http://www.usmo.com/~joewing/
>>
>>>> . . .
>>>>PIXEL_WHITE:
>>>> ld a, d ; 'a' now has X Coordinate
>>>> call GETPIX ; Call the Pixel Routine from ZLIB
>>>
>>> cpl ; compliment output so that we have a pixel mask
>>>
>>>> AND (hl) ; 'AND' to clear pixel
>>>> ld (hl), a ; Write the new byte to Graph Buffer
>>>> ld a, 0 ; Reload this for use with the CPs above
>>>> ret
>>>> . . .
>>
>
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