Font size changes when using rem (azw3 to epub)

patrik · 02-17-2017, 09:32 AM

I noticed a new book had a larger than usual base font size and thought that the original book was made like that. But when I compared (with Calibre viewer) the original azw3 the font size is smaller than for the converted epub.

After comparing and testing css's etc. it seems that the original has a base font size set to 0.83rem. This becomes 1.2rem in the converted epub resulting in the larger font size.

Why is this? I have searched the forum and read the calibre manual without finding any clue. The "Disable font size rescaling" is on. I buy most of my books from Amazon and convert books regularly which almost always work fine.

After checking some other books that had the same font size for azw3 and epub, I noticed that all those books have the base font set in em. The problematic book is set in rem. If I just change "rem" to "em", the converted epub uses the exact same value. (There is no font size set in html.)

azw3 font-size: 0.83rem; becomes epub font-size: 1.2rem;
azw3 font-size: 0.83em; becomes epub font-size: 0.83em;

The css class is used in <body class="xxx".

Not a big problem and easily changed, but I'm curious why this happens and what is the best way to get the same font size in the converted epub.

JSWolf · 02-17-2017, 09:41 AM

Do not convert KF8 to ePub. That's not the best way to do it. Install the KindleUnpack and do a KF8 to ePub and KindleUnpack will shift the KF8 code to ePub. Then load the ePub into the Calibre Editor and check the eBook. Fix any errors that show and when the check shows no errors, you are done and you'll have an ePub that's just like the KF8.

kovidgoyal · 02-17-2017, 09:48 AM

I cannot reproduce, converting the following html

Code:

<!DOCTYPE html>
<html>
    <head>
        <title>test</title>
        <meta charset="utf-8" />
    </head>
    <body>
        <p style="font-size: 0.8rem">Hello i love yuou</p>
    </body>
</html>

results in the following stylesheet.css (with font rescaling turned off)

Code:

.calibre {
    display: block;
    padding-left: 0;
    padding-right: 0;
    margin: 0 5pt
    }
.calibre1 {
    display: block;
    font-size: 0.8rem;
    margin: 1em 0
    }

patrik · 02-17-2017, 09:50 AM

I do that sometimes but most of the time you get one huge xhtml-file which you may want to split in separate files which takes time, and Calibre-conversions seem to work almost always.

But I just tried doing it with this book, and the font-size in the resulting epub retained the same font size (0.83rem).

But why did Calibre change it? Still curious...

Thanks.

patrik · 02-17-2017, 09:58 AM

Hmm, I just used the ScrambleEbook to send you a copy, but when I convert _that_ azw3 the resulting epub has the same font-size (0.83rem)...???

Is there something strange in my original azw3?

JSWolf · 02-17-2017, 10:38 AM

When you get a single HTML, it's usually a self-published eBook because a lot of self-published authors have no clue how to make an eBook. The real publishers use their ePub version as the source and those ePubs are already split.

I still suggest code shifting even if you have to split into the various chapters/parts.

kovidgoyal · 02-17-2017, 10:48 AM

Impossible to say without access to the original azw3 -- the one thing to check is to make sure that font rescaling was actually turned off, look at the job log for the ocnversion and search for font_rescaling

BetterRed · 02-17-2017, 03:16 PM

Quote:

Originally Posted by patrik

I do that sometimes but most of the time you get one huge xhtml-file which you may want to split in separate files which takes time, and Calibre-conversions seem to work almost always.

@patrik : for conversion to EPUB, try setting the following preferences to create a file per chapter

Conversion->Structure->Detect chapters at (XPath expression): to something other than '/', I use a slightly modified version of the default.

Conversion->Structure->Chapter mark: to pagebreak

Conversion->EPUB Output->Do not split on page breaks : unchecked

BR

patrik · 02-18-2017, 05:13 AM

Thanks BetterRed.

I do get split files when I use the normal Calibre conversion. It is when I use kindleunpack I end up with the whole book in one single xhtml-file. It is then I want to split up the file, and doing an epub->epub Calibre conversion I assume would negative the point of using kindleunpack in the first place?

(This is mostly a "problem" for me for one certain author-group that makes non-fiction books I like. It seems they start with Word and end up with an azw3 without any headers or internal toc. Since it's an non-fiction I tend to read every now and then and use the toc. Sometimes I have edited a book, changed all title headings to actual <h#> and created a toc. Maybe this can be done automatically by Calibre?)

BetterRed · 02-18-2017, 04:05 PM

Quote:

Originally Posted by patrik

It is when I use kindleunpack I end up with the whole book in one single xhtml-file. It is then I want to split up the file, and doing an epub->epub Calibre conversion I assume would negative the point of using kindleunpack in the first place?

I don't buy ebooks from Amazon so I'm not familiar with kindleunpack, but as far as I can make out it converts Amazon's proprietary formats into epub. I wouldn't think a subsequent epub->epub conversion would do any harm, it may even do some good

Give it a try.

Quote:

Originally Posted by patrik

(This is mostly a "problem" for me for one certain author-group that makes non-fiction books I like. It seems they start with Word and end up with an azw3 without any headers or internal toc. Since it's an non-fiction I tend to read every now and then and use the toc. Sometimes I have edited a book, changed all title headings to actual <h#> and created a toc. Maybe this can be done automatically by Calibre?)

It should be possible to solve the missing h# headers problem via the Conversion->Structure->Chapter Detection expression, see the XPath Tutorial and that should give you an internal (ncx) TOC. There's also a TOC Tool feature, you may need to add it to a toolbar (that's as much as I know about it).

BR

JSWolf · 02-18-2017, 06:08 PM

Quote:

Originally Posted by patrik

Thanks BetterRed.

I do get split files when I use the normal Calibre conversion. It is when I use kindleunpack I end up with the whole book in one single xhtml-file. It is then I want to split up the file, and doing an epub->epub Calibre conversion I assume would negative the point of using kindleunpack in the first place?

Yes, converting would negate using KindleUnpack. Use KindleUnpack and then load the ePub into the Editor. If you find it to be too much of a problem to split, then dump the ePub and convert. Otherwise, split. In most cases, it will be OK. So try it.

Quote:

(This is mostly a "problem" for me for one certain author-group that makes non-fiction books I like. It seems they start with Word and end up with an azw3 without any headers or internal toc. Since it's an non-fiction I tend to read every now and then and use the toc. Sometimes I have edited a book, changed all title headings to actual <h#> and created a toc. Maybe this can be done automatically by Calibre?)

With these author group, code shift is best as you'll need to fix it up anyway.

02-17-2017, 09:32 AM	#1
patrik Guru Posts: 682 Karma: 4568205 Join Date: Jan 2010 Location: Sweden Device: Kobo Forma	Font size changes when using rem (azw3 to epub) I noticed a new book had a larger than usual base font size and thought that the original book was made like that. But when I compared (with Calibre viewer) the original azw3 the font size is smaller than for the converted epub. After comparing and testing css's etc. it seems that the original has a base font size set to 0.83rem. This becomes 1.2rem in the converted epub resulting in the larger font size. Why is this? I have searched the forum and read the calibre manual without finding any clue. The "Disable font size rescaling" is on. I buy most of my books from Amazon and convert books regularly which almost always work fine. After checking some other books that had the same font size for azw3 and epub, I noticed that all those books have the base font set in em. The problematic book is set in rem. If I just change "rem" to "em", the converted epub uses the exact same value. (There is no font size set in html.) azw3 font-size: 0.83rem; becomes epub font-size: 1.2rem; azw3 font-size: 0.83em; becomes epub font-size: 0.83em; The css class is used in <body class="xxx". Not a big problem and easily changed, but I'm curious why this happens and what is the best way to get the same font size in the converted epub.

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02-17-2017, 09:41 AM	#2
JSWolf Resident Curmudgeon Posts: 79,680 Karma: 145864619 Join Date: Nov 2006 Location: Roslindale, Massachusetts Device: Kobo Libra 2, Kobo Aura H2O, PRS-650, PRS-T1, nook STR, PW3	Do not convert KF8 to ePub. That's not the best way to do it. Install the KindleUnpack and do a KF8 to ePub and KindleUnpack will shift the KF8 code to ePub. Then load the ePub into the Calibre Editor and check the eBook. Fix any errors that show and when the check shows no errors, you are done and you'll have an ePub that's just like the KF8.

02-17-2017, 09:50 AM	#4
patrik Guru Posts: 682 Karma: 4568205 Join Date: Jan 2010 Location: Sweden Device: Kobo Forma	I do that sometimes but most of the time you get one huge xhtml-file which you may want to split in separate files which takes time, and Calibre-conversions seem to work almost always. But I just tried doing it with this book, and the font-size in the resulting epub retained the same font size (0.83rem). But why did Calibre change it? Still curious... Thanks.

02-17-2017, 09:58 AM	#5
patrik Guru Posts: 682 Karma: 4568205 Join Date: Jan 2010 Location: Sweden Device: Kobo Forma	Hmm, I just used the ScrambleEbook to send you a copy, but when I convert _that_ azw3 the resulting epub has the same font-size (0.83rem)...??? Is there something strange in my original azw3?

02-17-2017, 10:38 AM	#6
JSWolf Resident Curmudgeon Posts: 79,680 Karma: 145864619 Join Date: Nov 2006 Location: Roslindale, Massachusetts Device: Kobo Libra 2, Kobo Aura H2O, PRS-650, PRS-T1, nook STR, PW3	When you get a single HTML, it's usually a self-published eBook because a lot of self-published authors have no clue how to make an eBook. The real publishers use their ePub version as the source and those ePubs are already split. I still suggest code shifting even if you have to split into the various chapters/parts.

02-17-2017, 10:48 AM	#7
kovidgoyal creator of calibre Posts: 45,320 Karma: 27111242 Join Date: Oct 2006 Location: Mumbai, India Device: Various	Impossible to say without access to the original azw3 -- the one thing to check is to make sure that font rescaling was actually turned off, look at the job log for the ocnversion and search for font_rescaling

02-18-2017, 05:13 AM	#9
patrik Guru Posts: 682 Karma: 4568205 Join Date: Jan 2010 Location: Sweden Device: Kobo Forma	Thanks BetterRed. I do get split files when I use the normal Calibre conversion. It is when I use kindleunpack I end up with the whole book in one single xhtml-file. It is then I want to split up the file, and doing an epub->epub Calibre conversion I assume would negative the point of using kindleunpack in the first place? (This is mostly a "problem" for me for one certain author-group that makes non-fiction books I like. It seems they start with Word and end up with an azw3 without any headers or internal toc. Since it's an non-fiction I tend to read every now and then and use the toc. Sometimes I have edited a book, changed all title headings to actual <h#> and created a toc. Maybe this can be done automatically by Calibre?)

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