Kobo Aura 6" thumbnails and tiles

[PYL]

Hi everyone,

I have recently bought a Kobo Aura, and I have a recurrent problem with books thumbnails and tiles that I don't seem to be able to solve, with personal epub books that I upload on the device.

Namely, I initially did not get the formatting of the covers right in my epub files, and neither the covers nor the thumbnails would show up right; by right, I mean that I expected the cover to be centered when opening the book, and the thumbnails to be maximized (except for the white borders which I have seen in this forum to be a recurrent problem, but I am not trying primarily to address this white border issue, although I would be interested in a fix if one is produced at some point).

I did solve the cover problem by proper modification of the epub source, but for some reason, the device does not update properly the thumbnails and tiles, even if I manually remove the images in the .kobo-images folder. The behavior shows up whether I remove the book from the device menu, or manually. I use Calibre (latest version) to upload the books.

As a matter of fact, the device is able to display thumbnails and tiles even though the associated images (.parsed files) are no longer present on the disk, so that the problem is not due to any css/html syntax problem. I did not find any other place in the accessible disk space where these could be stored (I even looked in the database), so I gather that they are stored in the hidden system partition, somehow, and for some reason don't get updated when the book is updated.

The only workaround I have found is to make the book appear as completely new, either by changing the author name (changing the first name by its initials, for example) or the title itself. I tried to modify the book structure (number of text files, for example) but this did not seem to improve the problem. However, this is clearly not a very satisfactory way to address this issue.

Apparently, the thumbnails and tiles seem to be updated after some time through some seemingly random access to the relevant books either through collections, home menu or whatever, but I have not been able to understand what triggers this update, and this does not seem to be systematically the case anyway, at least from the limited number of random tries I have made.

My kobo device runs on the latest firmware (as noted elsewhere on this forum, there is no choice about this, the device asks an update at first start). Epub editing is performed either with Sigil (last available version) or Calibre's internal epub editor.

Thanks in advance for any insight into this problem.
PYL

[davidfor]

You have tried a lot of things but missed one: power off and on.

The device caches the cover images for a few books in memory. Removing the book or the images will not remove them from the cache. They will eventually drop out of the cache as you open other books, but, I don't know how many covers are kept in the cache. Powering off and on will mean the cache is restarted and covers are read from the saved image files or regenerated from the books.

The white strips down the side are not a bug. The device generates the covers by rendering the first page of the book and using what would be displayed. If that has stripes down the side, then that is what is shown in the covers. That might not seem smart, but if that first page is something other than a single image, it works well. If you don't like this, you either create covers that fill the screen or you send the covers with the book from calibre. The Kobo driver has options to do this.

Also, as you are using calibre, you might want to try my Kobo Utilities plugin. Among other things, it has options to send the covers separately or remove them from the device so they can be regenerated. This doesn't cause the cache to be refreshed, but, it is usually easier to do than track down the covers on the device and do this manually.

[PYL]

Thanks for the quick answer. Old, but nice trick; I am still not used to think of these devices as specialized computers.

Thanks also for the other piece of advice about Kobo Utilities. I actually did use it (after quite a few manual uploadings and further search on the forum), but as I did not think of restarting the device, it did not help (yet). About the image white borders, I am not sure that we speak of the same thing here. The kobo device creates thumbnails and tiles .parsed files without white borders for 4:3 images aspect ratio, but they nevertheless show up with a thin white strip. Same thing if I create the images manually (correct size and then correct renaming) or if I use the Kobo utilities. I have read somewhere on this forum that some people are bugged by this behavior, especially that it does not happen with kepub (as I don't yet have a kepub book, I can't check this statement), but for now, this is alright with me, even though I am interested in any possible fix (assuming that this is indeed some kind of a bug and not a "feature").

Last but not least: would you by chance know of a reasonably simple and reasonably fast way of looking at the content of the hidden firmware partition: it does not show up, either in Windows or Linux (Ubuntu) disk management utilities. I saw on the forum that there is a way to dump the content on a micro-SD card, but this seems to be a lengthy process.

Best
PYL

[GeoffR]

If you send the epub covers with Calibre, their thumbnails will appear identical to kepub thumbnails.

The "white strips" that people (myself included) don't like are more apparent in older firmware, for example see the centre photo in this old thread. With the current firmware there is a white border around all thumbnails, so the white strips (which only occur when the device generates the cover, never when the cover is sent by Calibre) are not so obvious.

[PYL]

Thanks. I think I did not express myself correctly. I mean a thin white "border" (not strip) all around the cover in the thumbnails or tiles, even for 4:3 aspect ratio images, and even if I send the cover with Kobo utilities. I do see on your screen captures that there is indeed no such border, but there is one for mine. I just removed and resent a cover for one of my books which has a 4:3 cover, shut off and on the device, just to be sure I am not making wrong statements here, but this did not improve the problem. This issue may be specific for the Kobo Aura, I do not know.

Thanks for your help.
PYL

[davidfor]

If the device generates the cover for an epub, it depends on how the cover image is displayed. Some people like to fill the screen even if it distorts the cover image. With this, the generated cover will fill the screen during sleep or the space it is displayed in on the home screen. Personally, I display the cover image so that it is not distorted. This generally means space down either side. And that is displayed whenever the cover image is needed.

There are two options when sending the covers from calibre. One will resize them to be 4:3. That will fill the areas the covers are displayed in in, but will distort the cover if it is not originally 4:3. The other option will send it and respect the aspect ratio. That means the covers are not distorted, but when used as the screensaver, doesn't fill the screen.

Kepubs are different. An image file inside the book is marked as being the cover. This is extracted from the file and used. It is used at whatever aspect ration so when displayed as a screensaver will not fill the screen.

The post GeoffR pointed to shows examples of the three different cases using the old home screen.

As to access to the hidden partitions, it depends on what you want. The firmware update package contains the contents of the rootfs partition. Just unpack it to see what is on the partition. Or you can enable telnet and get access to it that way. I don't have a link for this, but a search here should find it.

[GeoffR]

Originally Posted by PYL

Thanks. I think I did not express myself correctly. I mean a thin white "border" (not strip) all around the cover in the thumbnails or tiles, even for 4:3 aspect ratio images, and even if I send the cover with Kobo utilities. I do see on your screen captures that there is indeed no such border, but there is one for mine. I just removed and resent a cover for one of my books which has a 4:3 cover, shut off and on the device, just to be sure I am not making wrong statements here, but this did not improve the problem. This issue may be specific for the Kobo Aura, I do not know.

The thin, even white border on all four sides appears on all book cover thumbnails in the current firmware, including kepubs bought from Kobo. This border is not the same thing as the white strips that occur when the device creates the cover from the first page of the book.

The pictures that show the thumbnails without the border are from older firmware, there is nothing you can do to remove the border in the current firmware, unless perhaps someone finds a firmware patch for it.

[PYL]

Thank you both. Quite helpful.

PYL