Thread: Converting (Kobo) epubs to reduce file size?
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Old 02-06-2014, 01:34 PM   #4
BobC
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Quote:
Originally Posted by jackie_w View Post
It may well be because the html files in Kobo-style epubs (kepubs) are full of extra <span> tags, e.g. <span class="koboSpan" id="kobo.32.1">some paragraph text</span>. These wouldn't be removed by a calibre conversion as it is perfectly valid code. A long book may have many thousands of them, which adds up.
Edit: The other likely suspects are embedded fonts and/or a lot of images.
The extra HTML markup will not contribute as much bloat as you might expect to the TOTAL book size. This is because of the mechanism used in the final zip compression of the component HTML files which tokenises commonly used "words".

A total size of 2-3Mb is likely to be, as mentioned, embedded fonts, assuming that both the Kobo and the OmniLit books both have the same images (or none at all).

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