Native or computer processed dithering for CBZ manga books?

[Jwing]

I have been reading manga on kindle. Processing the files with KCC.

In the last KOreader User Guide, there are steps for dither images using ImageMagick. Although, there is a native dithering function on koreader.

My question is which one is better? Native or Imagemagick? Or should I use both (process the image on computer and toggle on dithering on KOreader

Another question: jpg or png? Which is better on koreader (on kindle)?

Thank you

[NiLuJe]

The algorithm used in KOReader on devices without hardware dithering (i.e., yours) is actually ImageMagick's 8x8 ordered dithering .

It's pretty damn fine for this purpose; but Riemersma will look ever so subtly more natural (except it's been broken for years, so, use FloydSteinberg, which is almost as nice).

The main gain in going with preprocessing is the scaling process, though, not dithering; you'll get much nicer (and expensive) scaling with heavy-duty ImageMagick scalers.

(e.g., I use this script myself. Spoiler alert: it'll chomp on your CPU. A lot.).

[NiLuJe]

Originally Posted by Jwing

Another question: jpg or png?

PNG.

JPEG is lossy, and feeding it dithered content is the absolute worst thing you can do to a lossy compression algorithm: it'll absolutely ruin the dithering and fidelity, and make it very hard for the codec to actually do its job.

You're even likely to see *lower* filesizes with a properly encoded PNG for content dithered to the eInk palette anyway.