Why, During ePub to ePub Conversion does Calibre changes existing CSS classes?

JSWolf · 08-05-2011, 05:24 PM

I know is is off-topic, but it does have to do with converting ePub to ePub.

Why is it that when one converts ePub to ePub, that Calibre changes some of e existing CSS classes? Why can't Calibre leave things be and just modify what's been asked to be modified? Like if I specified to have different margins just change the margins or I just want to add in a cover image. To me, this makes no sense. It also makes changes that I don't actually want.

DoctorOhh · 08-05-2011, 06:41 PM

Moderator Notice
If you know it's off topic, then please create a new thread. Post moved to its own thread.

JSWolf · 08-05-2011, 10:23 PM

Because it just fit better over there.

DoctorOhh · 08-05-2011, 10:47 PM

Quote:

Originally Posted by JSWolf

Because it just fit better over there.

You added this to a thread about the "Original_ePub" feature. Not only didn't it fit better over there, the two topics are not related.

I hope you get your question answered by someone in the know.

Good Luck.

ldolse · 08-06-2011, 12:28 AM

I can see how the two topics are related, but the feature in that thread doesn't really address Calibre's css handling.

Anyway the css manipulation is integral to the conversion pipeline, as the css needs to be flattened and merged to support various conversion features. An ePub to ePub conversion which doesn't manipulate css would require a completely different conversion framework, which doesn't exist.

This is part of why the Modify ePub plugin is being developed, to cherry pick various pieces of the conversion pipeline and allow ePub manipulation without flattening the css.

itimpi · 08-06-2011, 03:05 AM

To rephrase Idolse's answer in a different way, it is worth remembering that the Conversion pipeline in Calibre at core is a three stage process:

Convert input into a common underlying representation (XHMTL) based
Carry out standarised manuiplulations of the XHTML internal representation. This stage woul dbe working on flattened CSS, and possibly producing revised CSS.
Convert XHTML based internal representation to a given output representation.

The phases are completely independent of each other. That is why the calibre plugin architecture works so well in providing great flexibility of conversion combinations as there are separate plugins for each input type and each output type. In fact there is no technical reason why you could not have a particular format with only an input or output type if the complementary plugin does not exist.

The fact that in an EPUB->EPUB conversion the input and output formats are the same does not change the overall process. Therefore the same manipulations of CSS and the like take place even if to a human perception they might be avoidable. The part that is doing that manipulation is not aware of the fact that the user selected the same input and output formats and that in this 'special' case that might not ALWAYS be necessary

JSWolf · 08-06-2011, 04:45 PM

But, can't things be changed so an ePub > ePub doesn't modify things that aren't asked to be modified? For one thing, if I have embedded font code, I end up with that being a really big mess. There is no way I want embedded font code in every XML file when it only needs to be in the CSS once. I cannot stand the 5pt margins added to every XML file. I don't like that some CSS gets modified and changed to calibre1 calibre2 etc while other CSS code is left alone.

The idea here is to get Calibre to not touch anything that's not being asked to be touched.

itimpi · 08-06-2011, 07:32 PM

I am afraid that the change you are asking for would not be practical without a radical design change to the way calibre operates.

As has been mentioned there are a number of initiatives to provide plugins that allow limited customisation of ePub files without running a conversion.

08-05-2011, 05:24 PM	#1
JSWolf Resident Curmudgeon Posts: 78,940 Karma: 144284074 Join Date: Nov 2006 Location: Roslindale, Massachusetts Device: Kobo Libra 2, Kobo Aura H2O, PRS-650, PRS-T1, nook STR, PW3	Why, During ePub to ePub Conversion does Calibre changes existing CSS classes? I know is is off-topic, but it does have to do with converting ePub to ePub. Why is it that when one converts ePub to ePub, that Calibre changes some of e existing CSS classes? Why can't Calibre leave things be and just modify what's been asked to be modified? Like if I specified to have different margins just change the margins or I just want to add in a cover image. To me, this makes no sense. It also makes changes that I don't actually want.

08-06-2011, 03:05 AM	#6
itimpi Wizard Posts: 4,553 Karma: 950151 Join Date: Nov 2008 Device: Sony PRS-950, iphone/ipad (Marvin/iBooks/QuickReader)	To rephrase Idolse's answer in a different way, it is worth remembering that the Conversion pipeline in Calibre at core is a three stage process: Convert input into a common underlying representation (XHMTL) based Carry out standarised manuiplulations of the XHTML internal representation. This stage woul dbe working on flattened CSS, and possibly producing revised CSS. Convert XHTML based internal representation to a given output representation. The phases are completely independent of each other. That is why the calibre plugin architecture works so well in providing great flexibility of conversion combinations as there are separate plugins for each input type and each output type. In fact there is no technical reason why you could not have a particular format with only an input or output type if the complementary plugin does not exist. The fact that in an EPUB->EPUB conversion the input and output formats are the same does not change the overall process. Therefore the same manipulations of CSS and the like take place even if to a human perception they might be avoidable. The part that is doing that manipulation is not aware of the fact that the user selected the same input and output formats and that in this 'special' case that might not ALWAYS be necessary

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08-05-2011, 06:41 PM	#2
DoctorOhh US Navy, Retired Posts: 9,888 Karma: 13806776 Join Date: Feb 2009 Location: North Carolina Device: Icarus Illumina XL HD, Kindle PaperWhite SE 11th Gen	Moderator Notice If you know it's off topic, then please create a new thread. Post moved to its own thread.

08-05-2011, 10:23 PM	#3
JSWolf Resident Curmudgeon Posts: 78,940 Karma: 144284074 Join Date: Nov 2006 Location: Roslindale, Massachusetts Device: Kobo Libra 2, Kobo Aura H2O, PRS-650, PRS-T1, nook STR, PW3	Because it just fit better over there.

08-06-2011, 12:28 AM	#5
ldolse Wizard Posts: 1,337 Karma: 123455 Join Date: Apr 2009 Location: Malaysia Device: PRS-650, iPhone	I can see how the two topics are related, but the feature in that thread doesn't really address Calibre's css handling. Anyway the css manipulation is integral to the conversion pipeline, as the css needs to be flattened and merged to support various conversion features. An ePub to ePub conversion which doesn't manipulate css would require a completely different conversion framework, which doesn't exist. This is part of why the Modify ePub plugin is being developed, to cherry pick various pieces of the conversion pipeline and allow ePub manipulation without flattening the css.

08-06-2011, 04:45 PM	#7
JSWolf Resident Curmudgeon Posts: 78,940 Karma: 144284074 Join Date: Nov 2006 Location: Roslindale, Massachusetts Device: Kobo Libra 2, Kobo Aura H2O, PRS-650, PRS-T1, nook STR, PW3	But, can't things be changed so an ePub > ePub doesn't modify things that aren't asked to be modified? For one thing, if I have embedded font code, I end up with that being a really big mess. There is no way I want embedded font code in every XML file when it only needs to be in the CSS once. I cannot stand the 5pt margins added to every XML file. I don't like that some CSS gets modified and changed to calibre1 calibre2 etc while other CSS code is left alone. The idea here is to get Calibre to not touch anything that's not being asked to be touched.

08-06-2011, 07:32 PM	#8
itimpi Wizard Posts: 4,553 Karma: 950151 Join Date: Nov 2008 Device: Sony PRS-950, iphone/ipad (Marvin/iBooks/QuickReader)	I am afraid that the change you are asking for would not be practical without a radical design change to the way calibre operates. As has been mentioned there are a number of initiatives to provide plugins that allow limited customisation of ePub files without running a conversion.

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