Quote:
Originally Posted by davidfor
That shouldn't be happening. The driver has the sizes for each cover type and device and generates a cover image from the cover in the calibre library. Unless I messed this up in a change earlier this year to clean up the code a bit. I haven't tested this with my Aura ONE, so I'll have a look tonight.
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Hi Davidfor, thanks for looking into it, I've tried a number of different combinations on my KA1.
Any 'upload covers' option results in a lower-res screensaver. Specifically, the KT driver, the KTE driver, and/or Kobo Utilities.
Here is an example (
kobo link for preview), I used this book because it's easier to see in the gradients below the "P" of the title:
image 1: cover image inside the book (when I start the book for the first time, not the screensaver)
For reference, the cover image is 1000x1500 in Calibre, and the original file in Calibre is epub, converted to kepub on transfer
image 2: screensaver image of the cover using 'upload covers' option
note, this has the 'keep aspect ratio' option unchecked, but the quality is the same for aspect ratio on/off, and greyscale on/off. It is the same overall effect for the KT/KTE drivers, or manual send cover with Kobo Utilities
Quote:
Originally Posted by davidfor
With the way this works, there shouldn't be a difference between polishing first and relying on calibre to update the cover during the send. They do function differently, but the effect should be the same. During the send, calibre looks for the cover image in the book and replaces it.
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When I use polish books on the original epub, then send the book over using the KTE driver, but 'upload covers' off, I get a high quality cover, example:
Image 3: high quality screensaver cover image via polish books
I should clarify, when I use the polish books option, the cover is momentarily blank on the KA1 after sending the book over (≤1s, but noticeable), then it seems to generate the cover.
Quote:
Originally Posted by davidfor
If it can't find the cover, it will add the image and mark it in the OPF as the cover but it won't be displayed while reading the book. Some of this can be turned off. In older calibre, if calibre couldn't determine which image was the cover, nothing was done. This was changed as it caused problems on some devices, but an option was added to turn it off. With this, if calibre can't replace the cover, then it should mean that the device won't find it either and it will use the default cover (title plus format name)
The Polish does largely the same (looks for the cover and replaces it if it can find it), but makes sure the cover image is displayed as the first page of the book. If the current cover can't be found, it adds the cover and a new first page in the book. This cover could be resized based on the conversion settings you normally use. But, if you have the output profile set to Tablet, the cover should be left full size.
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I have no idea how to change those options, but the cover does show when I open/read the book. In fact, the best version of the cover is when I open the book, because it appears to fill the whole screen, in high quality vs the tall aspect ratio with the black bars on the screensaver.
Quote:
Originally Posted by davidfor
With all that, you should be getting exactly the same cover image in the book in either way. And the device should be using it and resizing it in the same way. And because of how the cover image is extracted from the kepub, sending the covers using the driver has never been as useful as for epubs and other formats.
I'll have a play and see if I can see anything. Finding a book suitable for testing could be the problem.
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I get a distinct difference between polish covers + no 'upload covers' option selected in driver (good outcome) vs. 'upload covers' with the driver or koboutilities (bad outcome).
Also, If I select 'upload covers' in the driver or koboutilities
after polishing the book I still get the bad outcome.
Thanks for looking into it, is there anything else I can do to help investigate?
edit, additional details:
Calibre 3.7
KTE 2.8.2
Kepub reader/writer 2.7.1
Polish Books 1.0.0
Kobo Utilities 2.5.2