CbxConverter is a simple tool for converting comics (or other ) in CBR/ CBZ format to use WebP.
The program looks very basic, and isn't doing anything particularly clever. Essentially it's just converting JPGs to WebP, with some optional resampling to shrink file sizes even further.
This can still be enough to deliver good results. Our eight test files fell to 49.1% of their original size with the default compression settings, and only 16.7% after setting "Resize" to 50%.
Making this happen is more hassle than it should be, thanks to CbxConverter largely unfinished interface (all the basic tools are there, but you'll have to find them first, and even then they won't always work as you expect).
If you'd like to use this then you should also be sure your CBR/ CBZ reader can handle WebP images.
CbxConverter carries out its core function well enough, though, and if you need to batch process a group of comics then it could be all you need.
Version 0.8 brings (Changelog):
cwebp replaced with ImageMagick to allow more flexibility for input and output formats, in particular using CbxConverter only to resize and repack to cbz, keeping images in jpg format for platforms for which it may be hard to find reader with WebP support (iOS)
added "Output extension" (by default defining compression method) to settings
ImageMagick comes with most likely better resampling algorithms and overhelming list of options that may be even not possible to use at the moment, e.g. I don't know of comic book reader with support for FLIF
if upgrading - add -quality 75 in settings as extra parameter to keep same compression level
this version is not tested as much as 0.8.1 that emerged after several iterations with bugs fixed after reporting by users - if you need only WebP output you may prefer previous version or do not delete original files until checking content and compression level of files produced
The interface is horribly basic, but CbxConverter's resampling and JPG > WebP process really can cut CBR/ CBZ files down to size.