Thank you very much for this plugin, i've been enjoying books in kfx format on my kindle for a while now thanks to you. I always convert my books from epub 3 and the conversion goes well most of the time. There are just a few small things that i don't understand, mainly about the landmark elements of the toc/nav and a discrepancy between the results i get from converting the epub directly with Kindle previewer (v3.38) and the results i get from converting them with this plugin and reading them on my kindle (paperwhite 10th gen).
In old epub books that use the old method for landmarks in the .opf file like the example below, both kindle previewer and the converted kfx book give me the same result and everything works fine.
<guide>
<reference type="cover" title="Cover" href="cover.xhtml"/>
<reference type="toc" title="Table of Contents" href="toc.xhtml"/>
<reference type="text" title="Beginning" href="chapter001.xhtml"/>
</guide>
One cover, toc works, beginning points to the first chapter, everything's fine.
If the epub book uses the newer landmarks in the toc/nav file instead like the example below, kindle previewer will recognize the landmarks properly just like with the old method, but the converted kfx will not.
<nav epub:type="landmarks" class="hidden-tag" hidden="hidden">
<h1>Navigation</h1>
<ol class="none" epub:type="list">
<li><a epub:type="cover" href="cover.xhtml">Cover</a></li>
<li><a epub:type="toc" href="toc.xhtml">Table of Contents</a></li>
<li><a epub:type="text" href="chapter001.xhtml">Beginning</a></li>
</ol></nav>
With these new landmarks the kfx book on my kindle will display the cover twice and the "beginning" will point to the second cover instead of the first chapter. The cover link in the toc also points to the second cover. The toc seems to work fine otherwise. One weird thing i found is that if i flag the cover page as cover in calibre (adding the properties="calibre:title-page" to the cover.xhtml entry of the <manifest> in the .opf file), the double cover will be gone, but the "beginning" will still point to whatever page comes after the cover instead of the first chapter. Any idea why this is happening?
Another curiosity about images, it seems to me like the images in the kfx book are getting converted from rgb to grayscale (instead of simply making it a black and white rgb mode jpg) and gaining quite a bit of brightness in the process. Is it just my impression?