Calibre reducing cover resolution.

[pdurrant]

Originally Posted by dvpzoey

Ok, let me rephrase my question.

Let's take example of Kindle Paperwhite. It has a screen res. of 1448 x 1078 pixels (6" display).

For this device, cover res. should be at least 1448 x 1078 pixels.

I am getting a lot of info over this post. Thank you everyone: @Kovid, @pdurrant, @stumped, @JSWolf.

On a side note: how do I enter username in my post. does @user_name work here? Or do enter names manually.

There's no way to reference a member in a post so that they know about it. The best you can do is give Karma to someone by clicking on the Karma button on one of their posts that has been helpful (or amusing).

Bear in mind that the picture, unless it exactly matches the pixels of the display, will be getting resized by the (often low powered) processor of the ebook reader. For paperwhite it's even worse, as a colour image will be rendered as greyscale by that same low-power processor.

If you're only worried about how they look on the paperwhite, do some tests, and double-check that the size you quote won't get resized. Then create images of exactly that pixel count, and manually convert it to 16-level greyscale, using a high contrast filter in something like photoshop. You might also need to tweak the colour->greyscale conversion filter if there are some colours which need to be distinguished but come out at the same greylevel with the default.

But honestly, I doubt you'll see much difference from just havinga large pixel colour JPEG. So long as the cover is 1000 pixels in the long direction, I doubt you'll notice. Do some tests and find out if you can see the difference, and whether it' matters to you if you can!

[stumped]

There is definitely a case for making the image match the native resolution of the device. That is even more important with video, and gaming.
But for future proofing, if you have a larger image , store that also in calibre for use with some future device
Much also depends on how much time you will ever spend admring the cover image.
In my case that is never
I see thumbnails when choosing what to read next but my device sleep/wake cover hides the full screen cover image and opens to where I left off
To benefit from having excellent cover images you have to forgo using a cover ?

[dvpzoey]

thanks a lot everyone. Stumped, pdurrant thanks for your valuable and informative comments.

[michaelmcdonald]

I'm bringing this thread back to life because I seem to have a similar issue and I'm not entirely positive of how to correct it. In my library I have all my book with a cover image that matches size 1264x1680:



However, upon sending the book to the device (a Kindle Oasis) the cover art size is reduced to 376x500:



I'm not sure what's going on here or what I'm missing. I ran the Welcome Wizard and have selected the Kindle Oasis. Any thoughts on what's happening? Appreciate the help!!

[kovidgoyal]

The latter is a thumbnail. The kindles use much smaller thumbnails.

[michaelmcdonald]

Originally Posted by kovidgoyal

The latter is a thumbnail. The kindles use much smaller thumbnails.

Ah! So if I understand correctly: Calibre is showing the thumbnail version of the image when looking at the book that's on the device, while the image displayed as the "cover" while the screensaver is on will be the actual full-size image?

[kovidgoyal]

yes . though note that screensaver display in the Kindle is very flaky.

[michaelmcdonald]

I guess what's throwing me off is when I hover over the image while looking at the book on the device it's telling me "Cover size: 376x500".

[michaelmcdonald]

Originally Posted by kovidgoyal

yes . though note that screensaver display in the Kindle is very flaky.

As an additional follow-up question (really appreciate your assistance and great applications BTW! Kitty is outstanding!!): is there a way for me to verify the cover size for a file that's on my Kindle?

[kovidgoyal]

Use the ebook-meta --get-cover command on the file. It will extract the cover image.