[Conversion Output] KFX Output

[jhowell]

Version 1.52.0 - 17 May 2021

Detect Kindle Previewer versions up to 3.52.1. Version 3.52.1 removes YJImageLayoutEnhancer.

Better preserve the formatting of books from Standard Ebooks by allowing <br> elements with display:none styling. That styling was being removed by the plugin as part of the work around for a different problem.

Eliminate unnecessary Kindle Previewer conversion retries for unsupported book types such as comics.

[jhowell]

Amazon has released Kindle Previewer version 3.53.0. It is compatible with the current version of this plugin.

[Jaws]

Originally Posted by jhowell

That doesn’t work. It has to be a visible character or it is removed.

I don't have a recent (post-2015!) Kindle so I cannot test this on a current device, but the workaround I've used before in both straight-HTML (web page) applications and epubs is to define a one-point-line-height style and set the font color equal to the background. That "fools" the parser — that is definitely a "displaying" element between the <br/>s! — and it's easy to make into a simple cut-and-paste.

Here's one way to implement it, in HTML/epub code intended as input (and it also makes epubs work, since "number of paragraphs" can create problems):
<br/><span class="fnnewpar">.</span><br/>
and, in the stylesheet:
.fnnewpar {font-size: 1pt; line-height: 1pt; color: white}

One could also code this inline if there are only a few footnotes in the book, leaving the stylesheet alone:
<br/><span style="font-size: 1pt; line-height: 1pt; color: white">.</span><br/>
but that is a little more prone to errors and typos, and harder to deal with when proofreading.

Both methods work on a variety of .epub readers. So, over to you Kindle users for field testing...

[jhowell]

Originally Posted by Jaws

I don't have a recent (post-2015!) Kindle so I cannot test this on a current device, but the workaround I've used before in both straight-HTML (web page) applications and epubs is to define a one-point-line-height style and set the font color equal to the background. That "fools" the parser — that is definitely a "displaying" element between the <br/>s! — and it's easy to make into a simple cut-and-paste.

Doing that better hides the period, but it is not completely effective because KFX renderer is designed to try to make text more readable. For example, setting the text color to white does not hide it because the renderer adjusts colors for contrast against the current background color.

Even if the period is hidden the result will be footnote paragraphs with a full line of spacing between them, which is unlikely to match the formatting of the rest of the book. Further tweaks to the styling could improve this, but the result will probably not be consistent across the various Kindle apps, devices, and formats.

Doing this is fine for someone's own use, but if the intent is to format a book for publishing on the Kindle platform then it is best for now to avoid having multi-paragraph footnotes.

[jhowell]

Back to the original question...

Originally Posted by replicant

recently i started reading a book that has long footnotes and somehow the popups show only one paragraph of text (some footnotes have more than one parapragh). if the footnote has more than one <p> tag (thus another paragraph) the popup won't show it.

do you happen to know a way to fix that without having to remove the additional <p> tags?

I played around with this a bit more and came up with a hack that allows pop-up footnotes with multiple paragraphs in KFX format. The trick it to put a hidden border around the paragraphs that make up the footnote. This causes the KFX converter to group them together into a single block that will display in the footnote pop-up. Here is an example:

<p>This footnote example uses the aside element with the epub:type attribute and bi-directional
hyperlinks.<sup><a id="source" href="#ft-1-1" epub:type="noteref">1</a></sup></p>

...

<aside epub:type="footnote" style="border-style: hidden">
<p id="ft-1-1"><a epub:type="noteref" href="#source">1.</a> This is the footnote text.</p>
<p>This is another paragraph in the same footnote.</p>
</aside>

I tested it using current software. There is no guarantee that it will work in books converted by older or newer versions of the Kindle Previewer or displayed on older or newer versions of the KFX renderer. This works somewhat by chance so it would not be a great idea to rely on it in a published book.

[Jaws]

Originally Posted by jhowell

Doing that better hides the period, but it is not completely effective because KFX renderer is designed to try to make text more readable. For example, setting the text color to white does not hide it because the renderer adjusts colors for contrast against the current background color. {...}

I did say it was a workaround that I couldn't test on a recent Kindle...

Would using the HTML nonbreaking-space entity work better for Kindle users? Substituting & nbsp; (without the space) for the period works on the old Kindle that I have access to, including when the background is a different color. It works perfectly for .epubs and web-viewed HTML, and according to the old .mobi spec I looked at should work for .azw and .kfx (but like I said, I can't test it on anything that wouldn't qualify as a special deal from Honest Al's Used Cars).

Another alternative might be the Unicode en-space character U+2002 (& #8194; again without the space), but entering that can be tricky depending on the native keyboard setup on the machine used to edit the file so I defaulted to an entity designation. Same caveat: I can't test this on current equipment; I'm just suggesting it as a workaround that will be easy to modify later (because the code is so easy to search for and unlikely to overlap anything else).

The issue with a "full line space between" does not show up on the older Kindle that I'm using, or Kindle-for-PC. So I'm not sure about that...

[jhowell]

Originally Posted by Jaws

Would using the HTML nonbreaking-space entity work better for Kindle users?

Not for KFX format. It seems that two line breaks separated by non-breaking spaces are turned into a new paragraph in that format.

At this point I am done trying things out. If someone else does some testing of various alternatives perhaps other workable alternatives could be found.

[devil2trap]

Hi Jhowell,

Bro, first of all, I wanna thank you a lot for the KFX plugin. It really enhances the reading experience. Jhowell, I just have one question whether it is better to convert the book from epub to kfx OR from (mobi or azw3) to Kfx for Kindle reading. Does output quality get affected in any way or it remains the same irrespective of input format?

For instance, I have the same book in two formats in good quality
1) Epub size 10MB
2) Mobi size 6 MB

And I want to convert them into KFX format (for Kindle reading). So which one should I prefer or it doesn't matter.

[Axymeus]

Hello. I'm encountering an error when converting one of my EPUB with KFX Plugin. I've had no issue with my previous conversions and I can't pinpoint what exactly is different with this one. This is the output I'm getting

calibre, version 5.6.0
ERROR: KFX conversion failed: <p><b>Cannot convert</b><br><br><b>Conversion error:</b> Kindle Previewer error: Error:E00150: Internal error occured. java.lang.NullPointerException Exception in thread "main" java.lang.Exception: Failing conversion as the file was gracefully handled at com.amazon.adapter.common.app.EpubAdapterApp.b(Unk nown Source) at com.amazon.adapter.common.app.EpubAdapterApp.main( Unknown Source)</p>

Any help would be much appreciated thank you.

[JSWolf]

Originally Posted by devil2trap

Hi Jhowell,

Bro, first of all, I wanna thank you a lot for the KFX plugin. It really enhances the reading experience. Jhowell, I just have one question whether it is better to convert the book from epub to kfx OR from (mobi or azw3) to Kfx for Kindle reading. Does output quality get affected in any way or it remains the same irrespective of input format?

For instance, I have the same book in two formats in good quality
1) Epub size 10MB
2) Mobi size 6 MB

And I want to convert them into KFX format (for Kindle reading). So which one should I prefer or it doesn't matter.

Use ePub as the source format.

[JSWolf]

Originally Posted by Axymeus

Hello. I'm encountering an error when converting one of my EPUB with KFX Plugin. I've had no issue with my previous conversions and I can't pinpoint what exactly is different with this one. This is the output I'm getting

calibre, version 5.6.0
ERROR: KFX conversion failed: <p><b>Cannot convert</b><br><br><b>Conversion error:</b> Kindle Previewer error: Error:E00150: Internal error occured. java.lang.NullPointerException Exception in thread "main" java.lang.Exception: Failing conversion as the file was gracefully handled at com.amazon.adapter.common.app.EpubAdapterApp.b(Unk nown Source) at com.amazon.adapter.common.app.EpubAdapterApp.main( Unknown Source)</p>

Any help would be much appreciated thank you.

I suggest you try the latest Calibre, latest Kindle Previewer, and the latest version of the plugin. I cannot say this will work, but then it's a starting point instead of at least an older version of Calibre.

[jhowell]

Originally Posted by devil2trap

Jhowell, I just have one question whether it is better to convert the book from epub to kfx OR from (mobi or azw3) to Kfx for Kindle reading. Does output quality get affected in any way or it remains the same irrespective of input format?

It is usually better to convert from either EPUB or KF8 (azw3) since these support more rich formatting features, such as drop caps, that are not supported in MOBI format. MOBI is based on a very old HTML standard.

The provenance of files should also be considered. For example an EPUB that was created by conversion from MOBI format will convert no better than the original MOBI. Conversion can remove formatting in some cases, but it won't add it back in.

[jhowell]

Originally Posted by Axymeus

Kindle Previewer error: Error:E00150: Internal error occured. java.lang.NullPointerException

That error is caused by a failure of the Kindle Previewer. As JSWolf wrote check that you have the most recent version of the Kindle Previewer (3.53.0) installed. Amazon has fixed many bugs over time.

If that does not help then see the topic "Dealing with Conversion Errors" in the first post in this thread for other suggestions.

[devil2trap]

Originally Posted by jhowell

It is usually better to convert from either EPUB or KF8 (azw3) since these support more rich formatting features, such as drop caps, that are not supported in MOBI format. MOBI is based on a very old HTML standard.

The provenance of files should also be considered. For example an EPUB that was created by conversion from MOBI format will convert no better than the original MOBI. Conversion can remove formatting in some cases, but it won't add it back in.

Thanks for the reply Jhowell. I need to know one more thing, you have recommended using the " Tablet" instead of "Kindle" in page setup while conversion. But if I have a kindle paperwhite 3, won't it affect the quality of the page in kindle.

[jhowell]

Originally Posted by devil2trap

Thanks for the reply Jhowell. I need to know one more thing, you have recommended using the " Tablet" instead of "Kindle" in page setup while conversion. But if I have a kindle paperwhite 3, won't it affect the quality of the page in kindle.

The Output Profile conversion setting is used to determine how much to downsize images so that their resolution is no higher than the screen resolution of the device. This reduces file sizes, but these days e-readers have more storage available than in the past so that is no longer a very important consideration.

There is a downside to doing this in that it will prevent the use of the pinch-to-zoom function to magnify images to show more detail on the reading device.

The Paperwhite 3 output profile downsizes images to no more than 1072x1430 pixels. If you use that profile on a book contains a detailed map you will no longer be able to expand it see the fine detail. And even if you never zoom images, if you ever by a newer Kindle with a higher resolution screen you will need to reconvert your books to take advantage of it.

The Tablet profile essentially does no downsizing, leaving images at their original resolution. I recommend that for the highest quality results.