EPUB to AZW3: font sizes changed -- AGAIN!

Phssthpok · 12-22-2018, 09:03 AM

I had a problem earlier with this earlier (see this thread) which turned out to be due to not having checked "Disable font size rescaling" under Look & feel > Fonts.

Since then I have made this the default, and I spent three days reconverting all my EPUBs with "Use saved conversion settings" unchecked, to make sure that I don't get hit by a book which uses some old settings with font size rescaling enabled.

However, I now have another font size rescaling issue. One of my EPUBs (which looks perfectly normal) has <body> tags with no associated CSS. Looking at it with the Calibre editor, the "computed final style" text font size is 18pt (the usual default 1em size), but the converted AZW3 has <body class="calibre">, and the generated "calibre" CSS class contains a line which says "font-size: 12pt". On my Kindle, this is unreadably small, and I have to zoom in to size 11 (on a scale of 1 to 14) before it looks normal, which is size 4 for any other book.

I've looked at all the conversion settings and have tried various things to get rid of this (e.g. specifying a CSS rule for <body> with font-size: 1em in the EPUB), but it keeps insisting on generating an AZW3 with a 12pt font size, and the only way I can get rid of it is to manually edit the AZW3 after converting.

I've only found this one book with this problem so far, but I have no idea how many others might be affected...

Has anyone got any idea why this might be happening?

Phssthpok · 12-22-2018, 11:52 AM

I've just found another example. A chapter heading and subheading use these rules in the original EPUB:

Code:

.h2 {
  font-family: serif;
  text-align: center;
  text-indent: 0;
  margin-top: 3em;
  margin-left: 0;
  margin-right: 0;
  margin-bottom: 3em;
  font-weight: normal;
}
.h2a {
  font-family: serif;
  font-size: x-large;
  text-align: center;
  text-indent: 0;
  margin-top: 0;
  margin-left: 0;
  margin-right: 0;
  margin-bottom: 2em;
  font-weight: bold;
}

After conversion, what I end up with in the AZW3 is this:

Code:

.h2 {
    display: block;
    font-weight: bold;
    text-align: center;
    text-indent: 0;
    margin: 2em 0 1em
    }
.h2a {
    display: block;
    font-family: serif;
    font-size: 17pt;
    font-weight: bold;
    line-height: 1.2;
    text-align: center;
    text-indent: 0;
    margin: 0 0 2em
    }

So the main heading (<h2 class="h2">) ends up with the default H2 font size, but the subheading is reduced to 17pt, which looks tiny on my Kindle (about 50% of the size of the text in the chapter). In the Calibre editor, it looks quite normal: 17pt = 23px. The chapter text is 1em = 18px.

The margins are also changed in the main heading from 3em top and bottom to 2em top and 1em bottom.

It seems that all font sizes are being expressed in points, and 1em is being treated as equivalent to 12pt, and Kindle points are nothing like 1/72in. And it's also got its own ideas about what margins I should be allowed to have.

Phssthpok · 12-22-2018, 12:11 PM

As a sanity check, I converted again but with font size scaling enabled. (I disabled it earlier because my chapter headings were being shrunk). Suddenly all the generated font-size rules are expressed in ems instead of points, and it looks sensible again.

So it would seem that there is no way to get the font sizes in the EPUB accurately translated to the AZW3 -- either I end up with sizes in ems translated into incorrect sizes in points, or I let it change font sizes in ems into different font sizes in ems. Apart from which, it also changes my margins, whether I use font size rescaling or not.

It looks like I'll have to go for font rescaling, and waste another three days reconverting everything, unless someone can suggest an alternative...

Brett Merkey · 12-22-2018, 12:29 PM

Quote:

As a sanity check, I converted again but with font size scaling enabled. ... Suddenly all the generated font-size rules are expressed in ems instead of points, and it looks sensible again.

My work flow is much like yours, so I have been following and trying to understand the issues you have brought up in two threads. I edit in ePub and then convert to AZW3 for reading.

I always have "Disable Font Size Rescaling" checked in my Calibre "Common Options" dialog. The font sizes always emerge as em units--never pts or anything else. There may be some other issue at work here.

Phssthpok · 12-22-2018, 01:57 PM

Quote:

Originally Posted by Brett Merkey

My work flow is much like yours, so I have been following and trying to understand the issues you have brought up in two threads. I edit in ePub and then convert to AZW3 for reading.

I always have "Disable Font Size Rescaling" checked in my Calibre "Common Options" dialog. The font sizes always emerge as em units--never pts or anything else. There may be some other issue at work here.

Hmm, interesting. Do your margins stay the same size too?

As a kindness, could you please try creating a couple of <h2>s using the EPUB CSS I posted above and convert it, and see whether the resulting CSS comes out anything like mine?

Brett Merkey · 12-22-2018, 03:35 PM

Quote:

As a kindness, could you please try creating a couple of <h2>s using the EPUB CSS I posted above and convert it, and see whether the resulting CSS comes out anything like mine?

I did that and your snippet "font-size: x-large;" got converted to 17pt (!!!)

That is unexpected behavior to say the least. CSS keywords are meant to be translated at the user agent level, not in the stylesheet.

[This brings up a related issue: I have found that the Kindle PaperWhite does not handle CSS font-size keywords well. If your device font settings are not the default, the Kindle will display fonts at uncomfortably extreme sizes. I have created a Calibre regex-function which maps keywords to ems. I will post this in the Editor section.]

kovidgoyal · 12-22-2018, 10:05 PM

https://www.mobileread.com/forums/sh...d.php?t=186697

stumped · 12-23-2018, 01:55 AM

a 2 step work around to be going on with
1. calibre epub to epub conversion will replace the font size large, Xx large etc styles with sensible numbers... in Ems
2. then converting that output epub to azw should work well. ( everything i have used this workflow on, then placed on my Kindle PW3 has looked ok

I do step one will all newly added books,. arguably it is overkill but it clears out many glitches and annoyances before I even see them, and the output file CSS is easier to understand than some horrible publisher versions.
It also, with my additional settings, gets rid of any embedded fonts and simplifies font styles, and standardizes justification to what I want for reading fiction

Brett Merkey · 12-23-2018, 04:35 AM

@Phssthpok,
If Calibre routinely alters CSS font-size keywords during conversion, this could explain both the readability issues in the conversion result and the fact, as you report, that only some books have the problem.

I did not notice this Calibre behavior before you brought the issue up because I always convert those CSS keywords to ems in the epub *before* conversion to AZW3. I recommend avoiding this Calibre issue by using regex to blast away those CSS keywords in the epub. I posted my own workflow solution in the Editor section of this forum. This will allow you to maintain a more fluid control of typography. The translation of keywords to point units for a screen medium does not make much sense and should be avoided.

Phssthpok · 12-23-2018, 07:07 AM

Quote:

Originally Posted by kovidgoyal

https://www.mobileread.com/forums/sh...d.php?t=186697

"It is particularly important that you provide us with a way to reproduce your problem."

Done that, and problem was reproduced by Brett (to whom my thanks).

Phssthpok · 12-23-2018, 07:09 AM

Quote:

Originally Posted by stumped

a 2 step work around to be going on with
1. calibre epub to epub conversion will replace the font size large, Xx large etc styles with sensible numbers... in Ems
2. then converting that output epub to azw should work well. ( everything i have used this workflow on, then placed on my Kindle PW3 has looked ok

I do step one will all newly added books,. arguably it is overkill but it clears out many glitches and annoyances before I even see them, and the output file CSS is easier to understand than some horrible publisher versions.
It also, with my additional settings, gets rid of any embedded fonts and simplifies font styles, and standardizes justification to what I want for reading fiction

I think I'll do the same from now on.

Phssthpok · 12-23-2018, 07:13 AM

Quote:

Originally Posted by Brett Merkey

I did that and your snippet "font-size: x-large;" got converted to 17pt (!!!)

That is unexpected behavior to say the least. CSS keywords are meant to be translated at the user agent level, not in the stylesheet.

Thanks for verifying that this is something generic, not something specific to my setup.

I'm intrigued by the fact that it outputs ems with font rescaling turned on -- I presume the rescalingis done in ems, even though the rescaly wizard is in points.

And I still don't like the way it decides that it doesn't approve of my margin settings and changes them.

Brett Merkey · 12-23-2018, 07:45 AM

@Phssthpok,

Quote:

doesn't approve of my margin settings and changes them

When user agents (browsers; e-readers) deal with pts units, they seem to translate pts to absolute units--pixels. The results can be bizarre. A 150-px top margin for a 300dpi PaperWhite is 1\2 of an inch on the screen. For a 150dpi Samsung tablet, that translates to a full inch. Perhaps an unwanted difference.

Relative units like ems and %, in the long run, offer better solutions for screen devices.

Phssthpok · 12-24-2018, 08:38 AM

Quote:

Originally Posted by Brett Merkey

@Phssthpok,

When user agents (browsers; e-readers) deal with pts units, they seem to translate pts to absolute units--pixels. The results can be bizarre. A 150-px top margin for a 300dpi PaperWhite is 1\2 of an inch on the screen. For a 150dpi Samsung tablet, that translates to a full inch. Perhaps an unwanted difference.

Relative units like ems and %, in the long run, offer better solutions for screen devices.

Except my margins were in ems -- 3em top, 3em bottom, if you look above -- and these were translated into 2em top, 1em bottom. I could perhaps understand it if I started off in points (but I would still expect the top and bottom margins to come out the same size), but I don't understand why it takes it on itself to make arbitrary changes to my preferred settings.

Brett Merkey · 12-24-2018, 09:55 AM

Quote:

I don't understand why it takes it on itself to make arbitrary changes to my preferred settings

My conversion with your code respected your original values. No changes in the margins. Sorry I did not clarify that before. I was so shocked by the 17pt business! Remember also that I always have "font rescaling" turned off. In fact, over time, I have turned off any Calibre features I possibly can that contradict my desire to have full control over my code.

12-22-2018, 09:03 AM	#1
Phssthpok Age improves with wine. Posts: 559 Karma: 95229 Join Date: Nov 2014 Device: Kindle Oasis, Kobo Libra II	EPUB to AZW3: font sizes changed -- AGAIN! I had a problem earlier with this earlier (see this thread) which turned out to be due to not having checked "Disable font size rescaling" under Look & feel > Fonts. Since then I have made this the default, and I spent three days reconverting all my EPUBs with "Use saved conversion settings" unchecked, to make sure that I don't get hit by a book which uses some old settings with font size rescaling enabled. However, I now have another font size rescaling issue. One of my EPUBs (which looks perfectly normal) has <body> tags with no associated CSS. Looking at it with the Calibre editor, the "computed final style" text font size is 18pt (the usual default 1em size), but the converted AZW3 has <body class="calibre">, and the generated "calibre" CSS class contains a line which says "font-size: 12pt". On my Kindle, this is unreadably small, and I have to zoom in to size 11 (on a scale of 1 to 14) before it looks normal, which is size 4 for any other book. I've looked at all the conversion settings and have tried various things to get rid of this (e.g. specifying a CSS rule for <body> with font-size: 1em in the EPUB), but it keeps insisting on generating an AZW3 with a 12pt font size, and the only way I can get rid of it is to manually edit the AZW3 after converting. I've only found this one book with this problem so far, but I have no idea how many others might be affected... Has anyone got any idea why this might be happening? Last edited by Phssthpok; 12-22-2018 at 09:11 AM.

12-22-2018, 11:52 AM	#2
Phssthpok Age improves with wine. Posts: 559 Karma: 95229 Join Date: Nov 2014 Device: Kindle Oasis, Kobo Libra II	I've just found another example. A chapter heading and subheading use these rules in the original EPUB: Code: .h2 { font-family: serif; text-align: center; text-indent: 0; margin-top: 3em; margin-left: 0; margin-right: 0; margin-bottom: 3em; font-weight: normal; } .h2a { font-family: serif; font-size: x-large; text-align: center; text-indent: 0; margin-top: 0; margin-left: 0; margin-right: 0; margin-bottom: 2em; font-weight: bold; } After conversion, what I end up with in the AZW3 is this: Code: .h2 { display: block; font-weight: bold; text-align: center; text-indent: 0; margin: 2em 0 1em } .h2a { display: block; font-family: serif; font-size: 17pt; font-weight: bold; line-height: 1.2; text-align: center; text-indent: 0; margin: 0 0 2em } So the main heading (<h2 class="h2">) ends up with the default H2 font size, but the subheading is reduced to 17pt, which looks tiny on my Kindle (about 50% of the size of the text in the chapter). In the Calibre editor, it looks quite normal: 17pt = 23px. The chapter text is 1em = 18px. The margins are also changed in the main heading from 3em top and bottom to 2em top and 1em bottom. It seems that all font sizes are being expressed in points, and 1em is being treated as equivalent to 12pt, and Kindle points are nothing like 1/72in. And it's also got its own ideas about what margins I should be allowed to have. Last edited by Phssthpok; 12-22-2018 at 12:01 PM.

12-22-2018, 12:11 PM	#3
Phssthpok Age improves with wine. Posts: 559 Karma: 95229 Join Date: Nov 2014 Device: Kindle Oasis, Kobo Libra II	As a sanity check, I converted again but with font size scaling enabled. (I disabled it earlier because my chapter headings were being shrunk). Suddenly all the generated font-size rules are expressed in ems instead of points, and it looks sensible again. So it would seem that there is no way to get the font sizes in the EPUB accurately translated to the AZW3 -- either I end up with sizes in ems translated into incorrect sizes in points, or I let it change font sizes in ems into different font sizes in ems. Apart from which, it also changes my margins, whether I use font size rescaling or not. It looks like I'll have to go for font rescaling, and waste another three days reconverting everything, unless someone can suggest an alternative... Last edited by Phssthpok; 12-22-2018 at 12:20 PM.

12-23-2018, 04:35 AM	#9
Brett Merkey Not Quite Dead Posts: 194 Karma: 654170 Join Date: Jul 2015 Device: Paperwhite 4; Galaxy Tab	@Phssthpok, If Calibre routinely alters CSS font-size keywords during conversion, this could explain both the readability issues in the conversion result and the fact, as you report, that only some books have the problem. I did not notice this Calibre behavior before you brought the issue up because I always convert those CSS keywords to ems in the epub before conversion to AZW3. I recommend avoiding this Calibre issue by using regex to blast away those CSS keywords in the epub. I posted my own workflow solution in the Editor section of this forum. This will allow you to maintain a more fluid control of typography. The translation of keywords to point units for a screen medium does not make much sense and should be avoided. Last edited by Brett Merkey; 12-23-2018 at 04:39 AM.

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12-22-2018, 10:05 PM	#7
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12-23-2018, 01:55 AM	#8
stumped Wizard Posts: 3,305 Karma: 10259306 Join Date: May 2016 Device: kobo forma, Kobo Libra, Huawei media Tab, fire HD10, PW3 HDX8.9,	a 2 step work around to be going on with 1. calibre epub to epub conversion will replace the font size large, Xx large etc styles with sensible numbers... in Ems 2. then converting that output epub to azw should work well. ( everything i have used this workflow on, then placed on my Kindle PW3 has looked ok I do step one will all newly added books,. arguably it is overkill but it clears out many glitches and annoyances before I even see them, and the output file CSS is easier to understand than some horrible publisher versions. It also, with my additional settings, gets rid of any embedded fonts and simplifies font styles, and standardizes justification to what I want for reading fiction

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