Viewing KEPUBs in Calibre

BobC · 05-03-2014, 04:44 AM

I usually generate KEPUB files before transferring to my Glo, however I can't find a way to actually view the generated KEPUB on my PC before uploading.

As the KEPUB file within Calibre is structurally an EPUB, though with a different file extension, I would have hoped to be able to view it via the internal viewer but not so. In fact the only viewer I can find that will actually display them is CoolReader and that is by no means ideal as for some reason it won't display the TOC and also seems to ignore the internal css, preferring to rely on its own preferences.

Is it possible to allow the internal viewer to open these KEPUB files ?

BobC

davidfor · 05-03-2014, 05:47 AM

I don't think there is any real reason that the viewer couldn't open kepubs. It just needs someone to write some code. I'll have a look at it.

BobC · 05-03-2014, 05:56 AM

Thanks for the offer - if I simply change the extension to epub the viewer will open the file, it appears to be just allowing it to do that for a KEPUB extension that is needed.

BobC

BetterRed · 05-03-2014, 07:05 AM

Quote:

Originally Posted by BobC

Thanks for the offer - if I simply change the extension to epub the viewer will open the file, it appears to be just allowing it to do that for a KEPUB extension that is needed.

BobC

@BobC - when non EPUB formats are viewed in the calibre viewer they are first converted to temporary EPUB file - sometimes called a mini conversion. Assuming a KEPUB is just an EPUB with customisations the Kobo, then I imagine its a fairly faithful conversion - unlike a typical PDF.

BR

davidfor · 05-03-2014, 08:43 AM

Yes, because a kepub is basically an epub with some extras, that works. I can do it as an input plugin that subclasses the epub input plugin. The only complication is there needs to be something that detects and throws an error if there is DRM.

BobC: I'll send you a PM with something to test in a few minutes.

kovidgoyal · 05-03-2014, 08:55 AM

@davidfor: If you want to make it an input plugin, the input plugin will have to remove the kobo specific markup so that what it outputs is suitable for the rest of the conversion pipeline.

davidfor · 05-03-2014, 10:38 AM

Kovid: The extra markup are spans. The spans have a class and an id. They wrap each sentence in the book. Strictly, they are legal markup for an epub. If the input plugin was purely used by the viewer, it would be OK to leave them in. But, as it would also be used for conversions, it would be rude to leave them. There was some discussion in the Modify epub plugin thread on how to remove them. I'll have another look at this.

I also need to detect the Kobo DRM so that an error can be displayed. It isn't immediately obvious how as there isn't anything like the encryption.xml file.

The other thing that is needed with this is a metadata reader plugin. Again, subclassing the epub plugin works. The only thing that needs to be handled is the encrypted covers if there is DRM.

kovidgoyal · 05-03-2014, 10:41 AM

If the spans have some kind of consistent class/id name scheme they should be easy to identify and remove? If not, then I dont see how it is possible at all.

BobC · 05-03-2014, 11:12 AM

@Kovid
@Davidfor

I think this is getting away from my original ask. All I wanted was for the viewer to recognise that a file with a KEPUB extension doesn't need any sort of change to be viewable. This is easily proved when I rename these files (all of which have been created from an EPUB in the first place).

If the viewer would treat them as EPUB I can then associate KEPUB with the viewer at O.S level and be able to view the actual (un-reconverted) file by clicking on the KEPUB format in Calibre.

AIUI files from Kobo won't have .KEPUB extensions anyway (though I may be wrong as I have never bought one) so DRM isn't an issue.

If a small change to the viewer isn't practical then please, on my account, don't spend any more time on this - I'll live with CR3 and its imperfections as my check viewer. I only wanted it for simple checks not to read whole books; that's what I have the Glo for.

Thanks both.

@BR
I was aware of the "mini-conversion" carried out on non-EPUB books but as KEPUBs are EPUBS with a different file extension no conversion should be needed.

BobC

kovidgoyal · 05-03-2014, 11:56 AM

Simply viewing kepub files by treating them as epub is fairly easy to do. But I have no idea if kepubs can deviate significantly from epubs or not. In any case I have committed a change to have the viewer open kepubs by treating them as simple epubs.

cybmole · 05-03-2014, 12:05 PM

Quote:

Originally Posted by BobC

I usually generate KEPUB files before transferring to my Glo, however I can't find a way to actually view the generated KEPUB on my PC before uploading.

can't they simply be dropped into the Kobo desktop app, or would that be too good to be true?

BobC · 05-03-2014, 12:57 PM

Quote:

Originally Posted by cybmole

can't they simply be dropped into the Kobo desktop app, or would that be too good to be true?

I don't think so - these are not "official" KOBO KEPUBS but ones generated by jgoguen's conversion plug-in. In any case it would defeat the object of being able to look at the KEPUB with the same viewer as EPUB so I could see if anything had got changed in the conversion.

BobC

BobC · 05-03-2014, 12:59 PM

Quote:

Originally Posted by kovidgoyal

Simply viewing kepub files by treating them as epub is fairly easy to do. But I have no idea if kepubs can deviate significantly from epubs or not. In any case I have committed a change to have the viewer open kepubs by treating them as simple epubs.

@kovid,

Thanks - I'll see how it goes next week when the next version comes out.

BobC

cybmole · 05-03-2014, 01:45 PM

Quote:

Originally Posted by BobC

..... being able to look at the KEPUB with the same viewer as EPUB so I could see if anything had got changed in the conversion.

BobC

Well that is easy to do - you enable the extended driver preference that saves a copy of the kepub.epub to a folder after conversion , before sending it to device.Then you open that with sigil.
IF you use two instances of sigil, side by side , you can open the "before version" in the calibre library folder & the "after" version from wherever you specified & put them up in two windows.

davidfor · 05-03-2014, 09:44 PM

Quote:

Originally Posted by kovidgoyal

Simply viewing kepub files by treating them as epub is fairly easy to do. But I have no idea if kepubs can deviate significantly from epubs or not. In any case I have committed a change to have the viewer open kepubs by treating them as simple epubs.

A big thank you for that. I have just tested it from source and it is working perfectly.

As to the differences, other than the spans, the only thing I have been able to find is an attribute added to the manifest entry for the cover in the OPF. They have properties="cover-image" added. That won't pass an epub2 validator, but it doesn't seem to harm anything.

05-03-2014, 04:44 AM	#1
BobC Guru Posts: 691 Karma: 3026110 Join Date: Dec 2008 Location: Lancashire, U.K. Device: BeBook 1, BeBook Pure, Kobo Glo, (and HD),Energy Sistem EReader Pro +	Viewing KEPUBs in Calibre I usually generate KEPUB files before transferring to my Glo, however I can't find a way to actually view the generated KEPUB on my PC before uploading. As the KEPUB file within Calibre is structurally an EPUB, though with a different file extension, I would have hoped to be able to view it via the internal viewer but not so. In fact the only viewer I can find that will actually display them is CoolReader and that is by no means ideal as for some reason it won't display the TOC and also seems to ignore the internal css, preferring to rely on its own preferences. Is it possible to allow the internal viewer to open these KEPUB files ? BobC

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05-03-2014, 05:47 AM	#2
davidfor Grand Sorcerer Posts: 24,905 Karma: 47303824 Join Date: Jul 2011 Location: Sydney, Australia Device: Kobo:Touch,Glo, AuraH2O, GloHD,AuraONE, ClaraHD, Libra H2O; tolinoepos	I don't think there is any real reason that the viewer couldn't open kepubs. It just needs someone to write some code. I'll have a look at it.

05-03-2014, 05:56 AM	#3
BobC Guru Posts: 691 Karma: 3026110 Join Date: Dec 2008 Location: Lancashire, U.K. Device: BeBook 1, BeBook Pure, Kobo Glo, (and HD),Energy Sistem EReader Pro +	Thanks for the offer - if I simply change the extension to epub the viewer will open the file, it appears to be just allowing it to do that for a KEPUB extension that is needed. BobC

05-03-2014, 08:43 AM	#5
davidfor Grand Sorcerer Posts: 24,905 Karma: 47303824 Join Date: Jul 2011 Location: Sydney, Australia Device: Kobo:Touch,Glo, AuraH2O, GloHD,AuraONE, ClaraHD, Libra H2O; tolinoepos	Yes, because a kepub is basically an epub with some extras, that works. I can do it as an input plugin that subclasses the epub input plugin. The only complication is there needs to be something that detects and throws an error if there is DRM. BobC: I'll send you a PM with something to test in a few minutes.

05-03-2014, 08:55 AM	#6
kovidgoyal creator of calibre Posts: 45,252 Karma: 27110894 Join Date: Oct 2006 Location: Mumbai, India Device: Various	@davidfor: If you want to make it an input plugin, the input plugin will have to remove the kobo specific markup so that what it outputs is suitable for the rest of the conversion pipeline.

05-03-2014, 10:38 AM	#7
davidfor Grand Sorcerer Posts: 24,905 Karma: 47303824 Join Date: Jul 2011 Location: Sydney, Australia Device: Kobo:Touch,Glo, AuraH2O, GloHD,AuraONE, ClaraHD, Libra H2O; tolinoepos	Kovid: The extra markup are spans. The spans have a class and an id. They wrap each sentence in the book. Strictly, they are legal markup for an epub. If the input plugin was purely used by the viewer, it would be OK to leave them in. But, as it would also be used for conversions, it would be rude to leave them. There was some discussion in the Modify epub plugin thread on how to remove them. I'll have another look at this. I also need to detect the Kobo DRM so that an error can be displayed. It isn't immediately obvious how as there isn't anything like the encryption.xml file. The other thing that is needed with this is a metadata reader plugin. Again, subclassing the epub plugin works. The only thing that needs to be handled is the encrypted covers if there is DRM.

05-03-2014, 10:41 AM	#8
kovidgoyal creator of calibre Posts: 45,252 Karma: 27110894 Join Date: Oct 2006 Location: Mumbai, India Device: Various	If the spans have some kind of consistent class/id name scheme they should be easy to identify and remove? If not, then I dont see how it is possible at all.

05-03-2014, 11:12 AM	#9
BobC Guru Posts: 691 Karma: 3026110 Join Date: Dec 2008 Location: Lancashire, U.K. Device: BeBook 1, BeBook Pure, Kobo Glo, (and HD),Energy Sistem EReader Pro +	@Kovid @Davidfor I think this is getting away from my original ask. All I wanted was for the viewer to recognise that a file with a KEPUB extension doesn't need any sort of change to be viewable. This is easily proved when I rename these files (all of which have been created from an EPUB in the first place). If the viewer would treat them as EPUB I can then associate KEPUB with the viewer at O.S level and be able to view the actual (un-reconverted) file by clicking on the KEPUB format in Calibre. AIUI files from Kobo won't have .KEPUB extensions anyway (though I may be wrong as I have never bought one) so DRM isn't an issue. If a small change to the viewer isn't practical then please, on my account, don't spend any more time on this - I'll live with CR3 and its imperfections as my check viewer. I only wanted it for simple checks not to read whole books; that's what I have the Glo for. Thanks both. @BR I was aware of the "mini-conversion" carried out on non-EPUB books but as KEPUBs are EPUBS with a different file extension no conversion should be needed. BobC

05-03-2014, 11:56 AM	#10
kovidgoyal creator of calibre Posts: 45,252 Karma: 27110894 Join Date: Oct 2006 Location: Mumbai, India Device: Various	Simply viewing kepub files by treating them as epub is fairly easy to do. But I have no idea if kepubs can deviate significantly from epubs or not. In any case I have committed a change to have the viewer open kepubs by treating them as simple epubs.

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