What ePub page/position calculation methods are there?

[mattcurtis]

Hey guys,

I'm building an ePub reader, and I need to calculate and display the user's position inside of that ePub. However, ePub section/chapter size/word per page and and styling vary, which makes this a bit more difficult than I'd like.

I'm using a web-based solution, and since my implementation is page-oriented, I know what page a user is in, but only inside that section/chapter. Displaying all sections and calculating full number of pages and current page constantly uses too much memory. I was considering simply going with "Chapter X, Page X/X", but then this made me consider what other methods have been employed, or are recommended for letting the user know where they are in a book.

Thanks for any advice!

[DaleDe]

Adobe Digital Editions is the most popular reader for ePub. They use 1024 readable characters to determine a page size so no matter what size screen or font size there will be a one to one correspondence to the page number. You can read about this in our wiki and other issues with page numbers.

Dale

[Jellby]

Originally Posted by DaleDe

Adobe Digital Editions is the most popular reader for ePub. They use 1024 readable characters to determine a page size so no matter what size screen or font size there will be a one to one correspondence to the page number.

Not exactly that way. If I remember correctly, it's one page per 1024 bytes in the compressed file (so changing the compression level does change the number of pages), and then the pages are more or less evenly distributed by displayed characters (or maybe just characters, so comments and HTML code would count).

Ah, the relevant information is in the wiki: https://wiki.mobileread.com/wiki/Adob...s#Page_numbers

Originally Posted by mattcurtis

I'm building an ePub reader, and I need to calculate and display the user's position inside of that ePub. However, ePub section/chapter size/word per page and and styling vary, which makes this a bit more difficult than I'd like

Well, why not use a percent position? Beware of using the word "chapter", as not all books are split at chapter level, and even when they are the numbering could not match the actual chapter numbering, and that would be confusing.

[mattcurtis]

Originally Posted by Jellby

Not exactly that way. If I remember correctly, it's one page per 1024 bytes in the compressed file (so changing the compression level does change the number of pages), and then the pages are more or less evenly distributed by displayed characters (or maybe just characters, so comments and HTML code would count).

Ah, the relevant information is in the wiki: https://wiki.mobileread.com/wiki/Adob...s#Page_numbers



Well, why not use a percent position? Beware of using the word "chapter", as not all books are split at chapter level, and even when they are the numbering could not match the actual chapter numbering, and that would be confusing.

I've decided to go with percents.

[JSWolf]

Originally Posted by Jellby

Well, why not use a percent position? Beware of using the word "chapter", as not all books are split at chapter level, and even when they are the numbering could not match the actual chapter numbering, and that would be confusing.

Discworld books do not have chapters. So in the case of all of those books, using the term chapter would be incorrect. There also no X/X until the next chapter so that doesn't work as well.

[JSWolf]

Originally Posted by mattcurtis

I've decided to go with percents.

% alone is not OK. I'd prefer ADE style page numbers. Both would do very well.

[mattcurtis]

Originally Posted by JSWolf

% alone is not OK. I'd prefer ADE style page numbers. Both would do very well.

I'm using a sort of compromise: inside of a section, you see both where you are inside of its pages, and your overall percent inside of the book. Similar to Stanza.

Exact ADE style is a bit harder for me to implement at this point, but it's something I have planned out for the future.

[JSWolf]

Take a look at the count pages plugin for Calibre. It has the code to do the page count the ADE way and you can then implement it in your program from the start instead of in some update. Best do it that way then similar to Stanza (lousy program).

[Jellby]

Originally Posted by JSWolf

% alone is not OK. I'd prefer ADE style page numbers. Both would do very well.

Yes, "pages" would be fine to get an idea of the total length of the book. And it's very easy to calculate the total number of ADE-style pages, so one could have "95.00% of 20 pages" or "1.00% of 1900 pages" (both are "page 19"). Better yet, don't use the word "page", as it's misleading, maybe something like "block".

And having the relative position inside the current "chapter" is also a very useful feature, at least for the books that have chapters.

[mattcurtis]

Originally Posted by JSWolf

Take a look at the count pages plugin for Calibre. It has the code to do the page count the ADE way and you can then implement it in your program from the start instead of in some update. Best do it that way then similar to Stanza (lousy program).

I wish it was written in something more accessible than Python

[JSWolf]

Originally Posted by mattcurtis

I wish it was written in something more accessible than Python

You could ask the author for help with how its done to get the same page number as ADE.

[mattcurtis]

And part of my problem is that my reader will allow for extensive CSS customization (well, at least above the norm), and every time the user changes those CSS settings I will have to recalculate the number of pages, and ADE probably won't cut it if it's going to be accurate. I'll have to experiment with how long it takes to get full number of pages in large ePubs, see if that's feasible :/

[PeterT]

Actually I wold have thought that with the ADE style of page numbering, no degree of changes to the CSS would affect the page number. After all that is the whole idea behind the synthetic numbering. This is as opposed to the page numbers in (for instance) the Kobo ePub variant which reflects the actual screen count of pages.

[mattcurtis]

Originally Posted by PeterT

Actually I wold have thought that with the ADE style of page numbering, no degree of changes to the CSS would affect the page number. After all that is the whole idea behind the synthetic numbering. This is as opposed to the page numbers in (for instance) the Kobo ePub variant which reflects the actual screen count of pages.

Your saying that makes me think I don't understand ADE paging fully.

Back to researching.

[PeterT]

ADE page numbers are constant, regardless of things like font sizes / screen size etc. Roughly speaking, as others have said, they are based on a 1024 character chunk of the text; each 1k is a page.