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Forums > C64 Coding > De-Exomize directly to color RAM?
2014-11-20 20:23
TSM

Registered: Jan 2007
Posts: 43
De-Exomize directly to color RAM?

1) Can I achieve this with the 'sfx' command?
2) Can I do it with the 'mem' command and the decruncher sources included in my project?
3) Is it impossible, i.e. am I forced to decrunch the data somewhere else and copy it to color RAM afterwards?
2014-11-20 20:27
algorithm

Registered: May 2002
Posts: 707
Not recommended to depack directly to color ram if there is anything that requires d800 (e.g mcol bitmap etc, mcol char) unless you want to code a "glitch" demo.

The sfx self extractor does not overwrite IO area when depacking but rather, the ram underneath (maybe there are flags where io can be switched in)

Recommended to depack somewhere else, and then to plot to $d800 after
2014-11-20 20:41
Oswald

Registered: Apr 2002
Posts: 5127
if pack ratio is important, better use a custome routine since d800 needs only 4 bits, that is instant 50% gain.
2014-11-20 20:46
spider-j

Registered: Oct 2004
Posts: 505
No. 2) would be possible, although maybe not with the best pack ratio like Oswald said.
2014-11-20 20:49
tlr

Registered: Sep 2003
Posts: 1814
As said above, possible but what are you trying to achieve? Maybe there is a better solution?
2014-11-20 20:57
TSM

Registered: Jan 2007
Posts: 43
Quote: As said above, possible but what are you trying to achieve? Maybe there is a better solution?

The idea was to use Exomizer both for compression and to put every block of data where I need it. They are bitmap, screen and color of a multicolor picture, which I want to place at $E000, $D000 and $D800 respectively.
2014-11-20 20:59
Mixer

Registered: Apr 2008
Posts: 460
Do 2) modify decruncher to write how you like where you like. Writing to IO d800 colorram only keeps low 4 bits of byte. If you need high bits during the process or after, then keep a copy.
2014-11-20 21:05
TSM

Registered: Jan 2007
Posts: 43
Thank you all for your replies! I'll probably follow Mixer's advice.
2014-11-20 21:25
Mr. SID

Registered: Jan 2003
Posts: 425
What you're describing is pretty much exactly what I do in Donkey Kong Junior.
2014-11-20 22:21
j0x

Registered: Mar 2004
Posts: 215
Isn't this risky? Assume you want to fill $d800-$e100 with $01. Exomizer (I'm assuming it's decompressing forward) will probably write $01 into $d800 and then make a copy of length $8ff. However, the value read from $d800 (and onward) and copied may be $f1, not $01, which will corrupt your bitmap data.

If the decompression happens backwards, the same applies, except your screen data may get corrupted because of the high bits of $d800.
2014-11-20 23:02
Mixer

Registered: Apr 2008
Posts: 460
Cat loses its skin a few times. Risk is when there are unknowns.
 
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