Re: [cc65] Colormania (was: TGI summary)

From: Mark J. Reed <markjreed1mail.com>
Date: 2009-11-02 16:00:11
On Mon, Nov 2, 2009 at 9:51 AM, Groepaz <groepaz@gmx.net> wrote:
> On Montag 02 November 2009, Oliver Schmidt wrote:
>
>> - the next pixels to the right are in the byte with the next address
>> - there's a certain address offset to the bytes representing the
>> pixels in the next row
>
> both not true for c64 :)

Beat me to it.

C64 is organized in character-sized blocks:

AAAAAAAAIIIIIIII
BBBBBBBBJJJJJJJJ
CCCCCCCCKKKKKKKK
DDDDDDDDLLLLLLLL
EEEEEEEEMMMMMMMM
FFFFFFFFNNNNNNNN
GGGGGGGGOOOOOOOO
HHHHHHHHPPPPPPPP
aaaaaaaaiiiiiiii

If the A-pixels are in location $0400, then the B-pixels are in $0401, the
C-pixels in $0402, ... and the I-pixels in $0409.  Assuming the standard
320x200 resolution, the a-pixels are in $0428 and the i-pixels in $0430.  So
given an arbitrary point (x,y) and its location (say byte B bit b), you
can't assume anything about the location of any of its neighbor pixels
without special-casing on both x mod 8 and y mod 8.

-- 
Mark J. Reed <markjreed@gmail.com>

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Received on Mon Nov 2 16:00:17 2009

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