[GUI Plugin] Quality Check - Page 86

JSWolf · 10-18-2025, 05:02 PM

Are these eBooks displaying the cover twice doing so using the same cover image?

theducks · 10-18-2025, 05:52 PM

Quote:

Originally Posted by JSWolf

Are these eBooks displaying the cover twice doing so using the same cover image?

Jon If the cover (image and/or page was not declared properly, Calibre will not be able to replace it (cuz it does not know it IS a 'cover' ). Thus a cover and a image of a cover (the page with the image and the image file used)

It would take me about 1 minute to open the book in the editor (T), look at the first few entries and do what is needed (split out the cover image if part of a bigger file. This would also prevent the declaration of that file AS 'cover' since replacing that would delete all the rest that WAS NOT the cover), Run the debug and correct any other errors (leftovers).
IF the false cover was just a single file, using the browser part of the editor to delete, will also correct the TOC (if it referenced that file)

JSWolf · 10-21-2025, 11:04 AM

Quote:

Originally Posted by theducks

Jon If the cover (image and/or page was not declared properly, Calibre will not be able to replace it (cuz it does not know it IS a 'cover' ). Thus a cover and a image of a cover (the page with the image and the image file used)

It would take me about 1 minute to open the book in the editor (T), look at the first few entries and do what is needed (split out the cover image if part of a bigger file. This would also prevent the declaration of that file AS 'cover' since replacing that would delete all the rest that WAS NOT the cover), Run the debug and correct any other errors (leftovers).
IF the false cover was just a single file, using the browser part of the editor to delete, will also correct the TOC (if it referenced that file)

You can have the cover properly defined in the OPF and still have it displayed a second time. This is not about replacing the cover. This is about trying to automate removing the second display of the cover.

I know it's easy to fix this manually. But it's not currently possible to do this automatically.

Trester99 · Yesterday, 01:34 PM

My apologies, for such a delayed response. I didn’t know that that I had to “follow” my own thread to get notifications, I watched the thread for a couple of days and ended up working on other projects.

My knowledge of Calibre and ebook components is minuscule compared to you guys, but I “think” there are 3 different scenarios for duplicate covers. The following are notes that I had written back when I created the thread.

1.Embedded in HTML???
A 2nd cover (bad cover) shows up when viewing book, but it is not in the editor files.

Can be deleted using “Editing meta data for one book >>> Basic Metadata
1.select: "Set from ebook files"

2. The first two xhtml files will contain two different covers
A 2nd cover (bad cover) shows up when viewing book, The two covers are contained within the first two xhtml files when editing the book

Can be deleted by "Converting" the book
1. select: "Convert Books"
2. Select "Structure Detection"
3. Select "Remove First Image"

3. The two covers are located in the files "titlepage.xhtml" and "cover.xhtml". The cover name is always "cover.jpeg" (same cover) and is used in both files.
"In Calibre, a duplicate cover in an EPUB typically appears as an extra HTML file containing only the cover image, which results in the cover being displayed twice when viewing the book. This occurs because the EPUB format already specifies a cover through its metadata, and a separate HTML file for the cover creates a redundant entry.
You can remove the duplicate cover by using the Edit Book feature in Calibre and applying a regular expression in the Search and replace tool.
How a duplicate cover is embedded
When an EPUB is created or converted, a cover image is defined in the book's package file (content.opf) with an id and marked with properties=""cover-image"". Some programs, including Calibre during certain conversions, will also generate a separate HTML file (cover.xhtml) with an <img> tag pointing to the same cover image. The ebook reader then displays both the cover specified in the metadata and the cover in the HTML file, showing the same image twice. "

During this time, I found out about the option of “Removing First Image” in the Conversion process. I didn’t do a lot of sampling, but the option seemed to fix most/all of the duplicate cover issues. Having to convert all of the files is definitely not the preferred option, but most importantly some really smart person has already identified a methodology that can select ebooks with duplicate covers. My next step is to try and find the algorithm and see if it could be used in a plugin.

Yesterday I kinda glanced at the Polish feature of Calibre’s. I noticed the option to “update the cover in the book files”. I believe that this option is just updating the cover from what is stored in the metadata? How is it that the cover as listed in the html file can differ from the metadata?

Anyway, that is where I am at. Not sure when I’ll get back on it, but my plan was to develop a plugin that would at a minimum identify books with dup covers. If during the process I am able to figure out how to fix the issues, I would work towards that. As mentioned before, I don’t have a lot of background in Calibre and ebook structure so if anyone feels like taking on this type of project, I would be ecstatic!

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10-18-2025, 05:02 PM	#1276
JSWolf Resident Curmudgeon Posts: 80,903 Karma: 150249631 Join Date: Nov 2006 Location: Roslindale, Massachusetts Device: Kobo Libra 2, Kobo Aura H2O, PRS-650, PRS-T1, nook STR, PW3	Are these eBooks displaying the cover twice doing so using the same cover image?

Yesterday, 01:34 PM	#1279
Trester99 Member Posts: 15 Karma: 10 Join Date: Jun 2024 Device: Kindle Paperwhite	My apologies, for such a delayed response. I didn’t know that that I had to “follow” my own thread to get notifications, I watched the thread for a couple of days and ended up working on other projects. My knowledge of Calibre and ebook components is minuscule compared to you guys, but I “think” there are 3 different scenarios for duplicate covers. The following are notes that I had written back when I created the thread. 1.Embedded in HTML??? A 2nd cover (bad cover) shows up when viewing book, but it is not in the editor files. Can be deleted using “Editing meta data for one book >>> Basic Metadata 1.select: "Set from ebook files" 2. The first two xhtml files will contain two different covers A 2nd cover (bad cover) shows up when viewing book, The two covers are contained within the first two xhtml files when editing the book Can be deleted by "Converting" the book 1. select: "Convert Books" 2. Select "Structure Detection" 3. Select "Remove First Image" 3. The two covers are located in the files "titlepage.xhtml" and "cover.xhtml". The cover name is always "cover.jpeg" (same cover) and is used in both files. "In Calibre, a duplicate cover in an EPUB typically appears as an extra HTML file containing only the cover image, which results in the cover being displayed twice when viewing the book. This occurs because the EPUB format already specifies a cover through its metadata, and a separate HTML file for the cover creates a redundant entry. You can remove the duplicate cover by using the Edit Book feature in Calibre and applying a regular expression in the Search and replace tool. How a duplicate cover is embedded When an EPUB is created or converted, a cover image is defined in the book's package file (content.opf) with an id and marked with properties=""cover-image"". Some programs, including Calibre during certain conversions, will also generate a separate HTML file (cover.xhtml) with an <img> tag pointing to the same cover image. The ebook reader then displays both the cover specified in the metadata and the cover in the HTML file, showing the same image twice. " During this time, I found out about the option of “Removing First Image” in the Conversion process. I didn’t do a lot of sampling, but the option seemed to fix most/all of the duplicate cover issues. Having to convert all of the files is definitely not the preferred option, but most importantly some really smart person has already identified a methodology that can select ebooks with duplicate covers. My next step is to try and find the algorithm and see if it could be used in a plugin. Yesterday I kinda glanced at the Polish feature of Calibre’s. I noticed the option to “update the cover in the book files”. I believe that this option is just updating the cover from what is stored in the metadata? How is it that the cover as listed in the html file can differ from the metadata? Anyway, that is where I am at. Not sure when I’ll get back on it, but my plan was to develop a plugin that would at a minimum identify books with dup covers. If during the process I am able to figure out how to fix the issues, I would work towards that. As mentioned before, I don’t have a lot of background in Calibre and ebook structure so if anyone feels like taking on this type of project, I would be ecstatic!