[GUI Plugin] EpubSplit

[JimmXinu]

Functioning as designed, actually.

The checkboxes are for adding to the lines you have selected (and are turned blue). It's intended for users wanting to always include some of the front/end matter while using the normal (blue) select to choose for each individual split book.

If you don't need that feature, you can disable it to avoid confusion. The EpubSplit dialog has a Configure button for convenience.

[theducks]

I have been using it wrong accidentally all this time

[theducks]

I have been splitting a number of Amazon Boxed sets and noticed that once split, the fonts fail the check in the Calibre Editor (The EPUB source is still OK)
I tried copying (adding) the missing encryption.xml from the source (attached. The path matches).
No Joy. Is there another entry needed (and can the PI do this in the future )

[JimmXinu]

I have no idea what's in the source epub, let alone what's missing when split.

EpubSplit already copies over a number of different font file types. It should be possible to add more, if they can be identified:

Spoiler:

        ## always include font files for embedded fonts
        for key, value in six.iteritems(self.manifest_items):
            #print("manifest:%s %s"%(key,value))
            if key.startswith('i:') and value[1] in ('application/vnd.ms-opentype',
                                                     'application/x-font-ttf',
                                                     'application/x-font-truetype',
                                                     'application/font-sfnt'):
                self.add_linked_file(value[0])

Can you ScrambleEbook the source epub for me to look at?

[theducks]

It is a TTF
(<item id="id1" href="fonts/00017.ttf" media-type="application/x-font-truetype"/>)

But I think I spotted something (attached) in the full EPUB (it is 3.3M, which is why I did not scramble) . I tried a normal Add files (the font is there) and that does not put it in the META-INF (AFAIK split does not even try)

[JimmXinu]

I thought you said copying the encryption.xml file over didn't help? Does it work if it's in META-INF?

I'm not opposed to trying to copy over that file, but before you said copying it over didn't work...

[theducks]

Originally Posted by JimmXinu

I thought you said copying the encryption.xml file over didn't help? Does it work if it's in META-INF?

I'm not opposed to trying to copy over that file, but before you said copying it over didn't work...

I used the editor File Add. That did put it into META-INF , but it still did not work (when I open the Editor again).

calibre, version 7.5.1
ERROR: Failed to open book: Failed to open book, it has obfuscated fonts, but the obfuscation key is missing from the OPF. Do an EPUB to EPUB conversion before trying to edit this book.

But I can't see that in the source EPUB (and it works: attached)

[jhowell]

One thing to check is that splitting the EPUB did not change the identifiers in the OPF, specifically the one pointed to by unique-identifier in the package element. That identifier is used as the encryption key for font obfuscation.

[JimmXinu]

EpubSplit does set the identifier in content.opf. Since it's meant to be unique and all.
Example:

<?xml version="1.0" ?>
<package version="2.0" xmlns="http://www.idpf.org/2007/opf" unique-identifier="epubsplit-id">
   <metadata xmlns:dc="http://purl.org/dc/elements/1.1/" xmlns:opf="http://www.idpf.org/2007/opf">
      <dc:identifier id="epubsplit-id">epubsplit-uid-1707591258</dc:identifier>

But that could be (optionally?) copied from the source.

theducks, I'm still confused. You seem to be saying that you don't know how to make the split book work with encrypted fonts?

If you can't tell me exactly what needs to be copied/changed, and you can't share a source epub (or a scrambled version) so I can try to figure it out, I'm not going to be able to help you.

[theducks]

Even weirder. I went to scramble the split output (using scramble plugin) book
and

calibre, version 7.5.1
ERROR: ScrambleEbook [v0.6.0]: Source ebook must be de-DRM'd and in one of these formats:
- azw3
- epub
- kepub
- kepub.epub.

Please select another.

I can View the (split) book in Calibre.
It does split. Just fails the font (shows red shield until I added the encryption.xhtml), then it fails to load in the editor the next time
I just ran Scramble on the full Calibre Converted to EPUB (from AZW3) and that ran.

I will attach the scrambled source. Let me know, and I (or you can) remove it after you have grabbed it

Moderator Notice
attached epub removed as requested -- Jimm

[JimmXinu]

Okay, it looks like:

1. EpubSplit is copying the encrypted TTF file from the source, exactly as it is in the source epub.
2. For the split epub to use that TTF file, it needs the META-INF/encryption.xml file and the same <dc:identifier ...> value, as jhowell pointed out.

The exact problem, for me at least, was initially being masked by the fact that Calibre's Edit book automatically decrypts the TTF file when you open the epub and re-encrypts it again on save. (The older Explode book tool does not do that, BTW.)

Which leads to a couple interesting work arounds:

• You can copy the TTF file from the source epub while in Edit book because it's already decrypted at that point.
• You can delete META-INF/encryption.xml from the epub while in Edit book and when you save the epub, it won't re-encrypt the TTF file again. Splits after that are fine.

Clearly, Calibre knows how to decrypt the TTF file. The question then is whether EpubSplit should:

1. Copy the encryption.xml file and unique-id value.
2. Decrypt the TTF file like Edit book does, leaving it decrypted.
3. Re-encrypt the TTF file to the new unique-id value.
4. Do nothing and refer users to the work arounds above. Will DeDRM do anything about encrypted fonts?

I also have to consider what, if anything, should be done with EpubMerge about this. Multiple merged epubs will have different encryption.xml file and unique-id values.

While I think about think it, see the work arounds above.

[theducks]

(And I am glad you figured it out. I had no clue)
I am going to keep your suggested work around notes handy the next time it shows.
And I am sorry for opening the EPUB Merge can-o-worms

[Quoth]

Will DeDRM do anything about encrypted fonts?

I doubt it, but I don't know. I also doubt any Kindle mobi/azw or azw3/KF8 uses them.
I suppose an epub with Adobe DRM might.

[theducks]

Those books were part of a Amazon boxed set that I 'cleaned' so I could convert. Not the first time I have run into this, just got round-tuit in reporting.

[JimmXinu]

Originally Posted by Quoth

I doubt it, but I don't know. I also doubt any Kindle mobi/azw or azw3/KF8 uses them.
I suppose an epub with Adobe DRM might.

An epub->azw3 convert, the font file is left decrypted and there's not encryption.xml file.

Doing an epub->epub convert, the font file is still encrypted (or encrypted again).

Using DeDRM plugin and adding the epub to a library--if there's a way to invoke DeDRM other than file import I don't know it--the encryption on the TTF file is removed.

theducks - Did you need to DeDRM the original (prescrambled) epub? Can you confirm with the original epub that DeDRM removes the font encryption?