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#267025 ChenThread Image Format - Quality images on 1.8 ComputerCraft!

Posted by asie on 14 May 2017 - 03:28 PM in Programs

View PostBomb Bloke, on 14 May 2017 - 12:58 AM, said:

top left corner of the re-paletted image veers towards red.

#22282b is very slightly bluish. I am aware of what you're trying to point out, but I think I explained fully as to why it happens and how to mitigate it if such an effect is undesired.



#266990 ChenThread Image Format - Quality images on 1.8 ComputerCraft!

Posted by asie on 13 May 2017 - 05:46 AM in Programs

View PostBomb Bloke, on 13 May 2017 - 02:04 AM, said:

Did you maybe get the images mixed up? 0.2.0's non-paletted output is apparently showing lots more out-of-place blue / green pixels than 0.1.1's did?

They are not out of place, they're the best approximation of the given color. That's how error diffusion works - notice that the original color, more visible in the paletted output, is a little bit bluish. Applying heavy blur shows the same thing, like so. You can use --dither-level 0.7 or so to decrease that effect, however, like so:

Posted Image

You can also use the newly introduced ordered dither, because - due to a different algorithm - they do not propagate error in the same way error diffusion does, and as such avoid this side-effect. They also use a pattern for dithering, but at this time it is unfortunately not implemented as well as error diffusion, like so:

Posted Image

However, when the palette is closer to the original image, the ordered dithering algorithm shows results which are not far off in terms of quality from error diffusion, like so:

Posted Image



#266893 ChenThread Image Format - Quality images on 1.8 ComputerCraft!

Posted by asie on 08 May 2017 - 07:52 PM in Programs

View PostLignum, on 08 May 2017 - 07:48 PM, said:

Wow that was fast. I did expect the palettes to make a difference, but not to this degree. Kudos!

Actually, the CTIF rewrite made a fair amount of improvements as well!

Here's a comparison of the same image (almost) converted with CTIF 0.2.0 for non-paletted and paletted ComputerCraft:

Posted Image

Posted Image

And here's the same picture converted with CTIF 0.1.1 for non-paletted CC:

Posted Image

Ouch! As you can hopefully see, it's not just the addition of palettes; the algorithm improvements helped a lot as well.



#266890 ChenThread Image Format - Quality images on 1.8 ComputerCraft!

Posted by asie on 08 May 2017 - 06:33 PM in Programs

CTIFConverter 0.2.0 has been released! See the link in the first post (then go to Releases to download it).

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#266867 ChenThread Image Format - Quality images on 1.8 ComputerCraft!

Posted by asie on 07 May 2017 - 07:11 PM in Programs

It appears that ComputerCraft has added palettes in the latest Git version. I'll hopefully release an updated CTIF before that version comes out.

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