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Forums > CSDb Discussions > A little gfx conversion experiment..
2003-07-28 11:08
Vent

Registered: Jul 2003
Posts: 6
A little gfx conversion experiment..

On this page is presented step by step a conversion of a 24 bit test image to Drazlace format. Includes different C64 palettes for Adobe Photoshop etc.

I'd be glad to get ideas concidering the topic.

http://www.cs.tut.fi/~vtr/c64conv/
 
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2003-08-05 09:21
Ninja

Registered: Jan 2002
Posts: 411
if groepaz somewhen moves his ass away from the gamecube and continues working on his c64-projects, you can expect the ultimate converter tool somewhen. Well, if.. ;)
2003-08-05 22:55
White Flame

Registered: Sep 2002
Posts: 136
As far as the aspect ratio goes, every time I program some C64 graphics stuff on the PC, I set the screenmode to 640x400. Same aspect ratio as 320x200, but you get plenty of "offscreen" space, and you don't get that ugly scandoubling. I also run VICE in 640x400 (with Double Size turned off), getting the full border and proper aspect ratio.
2003-08-06 07:46
chatGPZ

Registered: Dec 2001
Posts: 11364
Oswald: the feature you mean is "despeckle" no? :o)

i would suggest some matrix/convolve based blur that preserves edges and blurs at adjustable radius and threshold.... some gaussian blur variants are good at this aswell.

Ninja: patience :o) atm its way to hot for _any_ sort of coding anyway :=P
2003-08-06 08:02
Oswald

Registered: Apr 2002
Posts: 5086
Groepaz: coreldraw simply calls it "smart blur", dunno what the algo's name could be.. but it also has a jaggy despeckle effect, so I think it would call it simply despeckle if it would be that :)
2003-08-06 08:59
MagerValp

Registered: Dec 2001
Posts: 1074
First of all, any graphics converter that works with RGB values is fundamentally flawed. Colour 0 is black, colour 1 is white, etc, regardless of the RGB values of the palette. Anything else is just silly, and leads to a dithered mess.

As for the aspect ratio, no, VGA 320x200 is not very close to the C64's aspect ratio, at least not on a PAL machine. The visible C64 resolution is closer to 384 x 288, with perfectly square pixels. It all depends on your TV/monitor of course, but it's not as stretched as a PC's 320x200.
2003-08-06 11:14
algorithm

Registered: May 2002
Posts: 705
Overall, The best results are achieved when actually drawing the picture from scratch rather than converting it. A good graphic artist will be able to utilise their own color transitions methods (hashing, stipples etc) on the image which in nearly all cases will look better than floyd steinberg dithering using conversion programs.

2003-08-06 12:09
Vent

Registered: Jul 2003
Posts: 6
Oh yes! And the conclusion is:
There should be a converter which works the way MagerValp described. And it should _not_ try to alter the picture in any way. If there are blocks with more colours than possible in the original image, the converter should just give an error message, and not try to fix or dither the image. This would prevent all the flaws.

In practice, that means that one could completely draw a picture on a decent pixelling program, and then just save the picture in a c64-compatible file format with this "converter" tool.

That kind of program should not be too hard to write? ;)

I think I have repeated myself.
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