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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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algorithm
Registered: May 2002
Posts: 705 |
The BMP2IFLI utility dithers the image based on pepto's C64 colour palette. |
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HCL
Registered: Feb 2003
Posts: 727 |
My thoughts as a coder (and sometimes gfxer): No converter will ever be able to *see* if it does well or not. All we can do is more or less smart algorithms that will optimize the conversion in some or another way. From an artistic point of view, this is useless.
Still i can imagine that a converter may be cool to have, and would do about 90% of the job. But *PLEASE* do those last 10% with your own hands, if you don't want to do all 100%. |
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Oswald
Registered: Apr 2002
Posts: 5086 |
jailbird:
increasing contrast and hue comes from experience...
ofcourse I didnt mean to turn the contrast to the maximum that your high tech gfx tool is capable of. just as much as the picture still looks good (=as much as possible).
and I still think increasing the hue level helps, as these operations will get all colors in the picture closer to the c64's palette. (wich has lot of maximum colors in rgb I mean f.e. max green 0 255 0.. )
also I didnt mean that usual blur routine, that you can find in all of those gfx tools. this is a special one wich will kill only the almost anyway invisible little details (low contrast stuffs, with almost no color differences.. but depends also on the settings), but it KEEPS the important details edges, etc. |
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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.. ;) |
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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. |
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chatGPZ
Registered: Dec 2001
Posts: 11352 |
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 |
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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 :) |
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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.
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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.
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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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