Re: A86: FindPixel
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Re: A86: FindPixel
On Tue, 23 Jun 1998 16:38:42 -0600 Dux Gregis <assets@eden.rutgers.edu>
writes:
>
>This looks like a find pixel routine: $4967
>Maybe for _plotSScreen?
yes, i've seen this routine, it treats it as a one-dimentional array, not
a grid like the screen. you can only get to the first 256 pixels, too.
there's also $496B which doesn't load hl to point to _FORMULA_BITMAP, if
you wanted to use this as find pixel, that's what you'd use.
$496B $24CD find bit hl+=a/8 a=1<<(a%8)
anyway call with:
hl->array ($4967 loads it as _FORMULA_BITMAP)
a=bit index
returns with:
a=bitmask
zero flag indicates bit status
de=bit # (original a&7)
bc is preserved
hl=byte where the bit is
>If its fp bits are in the same place in 1.2 as 1.3 (@ $24f6), then we
>can use those for a super fast video mem find pixel routine. Can
>someone check?
>BTW, the bits are in reverse.
well, in 1.2 at $24e8 there's 01 02 04 08 10 20 40 80
isn't there a rom 1.4? Thomas Bladh mentions it in the readme for BG
v1.0
-josh
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