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Forums > C64 Pixeling > converting graphics...
2006-01-15 21:58
spinal
Account closed

Registered: Jan 2005
Posts: 47
converting graphics...

I've started a GFX converter, just for fun.

I started by calculating the possible colors mixable from a fairly accurate C64 palette, and came up with the following 135 color palette (including the origional 16 C64 colors).


Using it, I did an RGB comparison to the 135 colors, an plotted the two colors which compose the mixed color on odd or even lines, ie, if the line being drawn was even, then color 1 was plotted, if odd, color 2. The result follows...

I have yet to do lo-res color reduction(3+background), but there is plenty of time for that.

I was wondering if anyone can offer advice for better quality output, I read in another post, that a luminosity check should be done first, then an RGB check (I assume only checking close luma values), I gave that a go first, but ended up with a very similar output.
 
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2006-01-20 00:46
algorithm

Registered: May 2002
Posts: 702
For heavens sake, forget the aspect ratio. just concentrate on good conversion.!! hybrid color dithering taking into account the mix colours will achieve good results..... wait and see
2006-01-20 12:26
Spinball

Registered: Sep 2002
Posts: 87
an optinal (and user-configurable) aspect ratio would be a nice and handy feature in a converter, me thinks.
2006-01-22 02:41
Nemezis
Account closed

Registered: Jan 2002
Posts: 22
I've tried to convert this picture in my way just to check the difference between this line-convertion and standard one. And here is the result (reduced color-set to 16, not prepared for C64 multicolor mode)


2006-01-22 14:52
Graham
Account closed

Registered: Dec 2002
Posts: 990
I would not compare colors in RGB space but in YUV space where Y is the dominant part. Also, you should weight colors to their flicker, for example white+black should never be used for lace.
2006-01-22 19:07
Oswald

Registered: Apr 2002
Posts: 5007
YUV space.. now thats a very nice info, I didnt thought of that. I will check how this method performs.
2006-01-23 08:09
MagerValp

Registered: Dec 2001
Posts: 1055
Colour space reduction is an interesting topic and all, but what we really need are good converters that work with 16-colour palettized images. This lets the artist draw in DPaint or whatever, and then have the results converted to a C64 format, without any dithering or other crap. Preferably it should generate an error if it can't fit all the colours in a cell, and not try to hide it with dithering or by choosing the nearest colour. Why aren't there more tools like this? There are 20-odd utilities that work with RGB/YUV and try to approximate stuff, but no one ever likes the result.
2006-01-23 10:16
Frantic

Registered: Mar 2003
Posts: 1626
Magervalp.. So unbelievably true. I really hate those tools that won't generate a 1:1 c64 image out of a 16 color palettized pc/amiga image. (Unless dithering and all that is explicitly turned on, as an option.)
2006-01-23 12:57
A Life in Hell
Account closed

Registered: May 2002
Posts: 204
Quote: Colour space reduction is an interesting topic and all, but what we really need are good converters that work with 16-colour palettized images. This lets the artist draw in DPaint or whatever, and then have the results converted to a C64 format, without any dithering or other crap. Preferably it should generate an error if it can't fit all the colours in a cell, and not try to hide it with dithering or by choosing the nearest colour. Why aren't there more tools like this? There are 20-odd utilities that work with RGB/YUV and try to approximate stuff, but no one ever likes the result.


Can't the gimp cbm file filters do this already?
2006-01-23 13:18
chatGPZ

Registered: Dec 2001
Posts: 11088
yes, and countless other tools. also such a converter is trivial to write for any format if you really want it :)
2006-01-23 19:27
Oswald

Registered: Apr 2002
Posts: 5007
Magervalp, my tool P1 lets you convert (dithered/not) AND rightaway edit the picture with the c64 restrictions in lot of formats. Then you may save it in bmp or c64 format.

/me rules
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