Quote:
Originally Posted by winstonma
- Support WebP, which is included in EPUB v3.3
- Support WebP within CBZ (reduce the size of comic book by 25-40%)
- (Nice to have) Support CB7
Using WebP can really reduce the image size, and thus shrink the size of the EPub/CBZ |
Ummm... you did notice the line that reads "
W3C Working Draft 06 April 2021"?
You might also want to check
Is WebP really better than JPEG? before repeating the 25% to 34% size savings claimed by Google.
In December, 2020, I did some testing on my epub collection with their average 1000-1125 x 1500 cover images which are compressed using the Mozilla JPEG compression. Using cwebp to compress 10,000 of the original cover files and resize them to match the current cover files yielded an output directory that was 5% larger than the directory with the mozjpeg compressed cover images.
As for supporting CB7? In compressing image files, I've found little advantage to using 7Zip's 7z archive over a more or less standard zip archive. The image files are already compressed and adding them to an archive does not yield much extra compression. In a quick test, I compressed 20 images from my camera. Using 7Zip's 7z archive format with everything set for maximum compression, the output archive was 197,101,971 bytes while using 7Zip's Zip format with normal compression yielded a 198,244,218 bytes output archive. I'm not sure if the time to create the 7z archive justified the 0.6% file size difference.