Aura Aura One: Epub Covers too small

[Gogolo]

Hi

As you can see in the attachment all the covers of my epubs are shown too small. I even created 1200x1600 covers in calibre but they are all too small. pdfs are ok.

Do you know the problem and solution?

Im on the latest firmware, ksm, autoshelf. Everything is working fine besides of this.

thx for your help.
Olivier

[GeoffR]

In your Calibre conversion settings make sure you have Page Setup > Output Profile set to Tablet. Don't use the Kobo Reader profile, that is only for old low-resolution Kobo devices, and will make the covers too small on newer devices.

But beware, if you have already converted books using the wrong profile then Calibre might keep using that same profile the next time you convert, it will only use the new profile for new conversions, so for those books you might need to manually change the output profile when you re-do the conversion.

Note that the above applies to the cover inside the book. Normally the device will use that cover to generate the thumbnail images. For better results with cover thumbnails you might also try enabling the "Upload covers" option in the KoboTouch driver. This causes Calibre to send the cover image to the device directly and so avoids the whitespace caused by the book's page margins.

Edit: Also beware that when you change the covers, you might need to turn the device off and restart it before the new covers will show up.

[Terisa de morgan]

Originally Posted by GeoffR

In your Calibre conversion settings make sure you have Page Setup > Output Profile set to Tablet. Don't use the Kobo Reader profile, that is only for old low-resolution Kobo devices, and will make the covers too small on newer devices.

My output profile is Kobo Reader, the same for all my devices (I think), and for what it matters Kobo Aura and Kobo Aura One and it was for a Kobo Mini before. I have selected the option, however, for upload covers.

[GeoffR]

Originally Posted by Terisa de morgan

My output profile is Kobo Reader, the same for all my devices (I think), and for what it matters Kobo Aura and Kobo Aura One and it was for a Kobo Mini before. I have selected the option, however, for upload covers.

With the upload covers option your thumbnails will be fine, but the Kobo Reader output profile will mean the images inside the book are be scaled down by Calibre during conversion and then (depending on the book's stylesheet) scaled up again to display. I think that will result in very poor image quality inside the book.

[JSWolf]

Not even about scaling up. It's about the loss of resolution and loss of readability. So for eBooks with images larger than 800x600, they get reduced. It's best to leave the images alone and set your output profile to tablet.

For a cover, you do want (if you can get) it to be at least the resolution of the device.

[Terisa de morgan]

Originally Posted by GeoffR

With the upload covers option your thumbnails will be fine, but the Kobo Reader output profile will mean the images inside the book are be scaled down by Calibre during conversion and then (depending on the book's stylesheet) scaled up again to display. I think that will result in very poor image quality inside the book.

I don't know, this is one of the covers in the Aura One (I'm not a good photographer).

[JSWolf]

Originally Posted by Terisa de morgan

I don't know, this is one of the covers in the Aura One (I'm not a good photographer).

You can see it's being scaled up.

[Terisa de morgan]

Originally Posted by JSWolf

You can see it's being scaled up.

Yes, but scaled up doesn't equal bad quality. Anyway, the user has the two options, I only wanted to confirm that the option for upload covers was enough and it worked well.

[Gogolo]

Thx for all your kind help! I directely copied the epubs to the device with windows explorer. Am I getting this right: 1. delete all epubs on aura one. 2. install kobo driver (how?) 3. export everything via calibre with tablet page layout.

ok? sorry, I'm all new to this.

[GeoffR]

Originally Posted by Gogolo

Thx for all your kind help! I directely copied the epubs to the device with windows explorer. Am I getting this right: 1. delete all epubs on aura one. 2. install kobo driver (how?) 3. export everything via calibre with tablet page layout.

ok? sorry, I'm all new to this.

You need to use Calibre to make use of the Upload cover options, if you copy the books to the device manually then you are stuck with whatever cover the device generates from the first page of the book, which is what you have now. You don't need to install any driver though, it comes built into Calibre.

The screenshot in this post shows the Upload covers configuration option in the KoboTouch driver.

You can also use the KoboUtilties plugin (which needs to be installed separately) to send the covers without re-sending the book, but you stillneed to have the book in Calibre and associated with the book on the device for that to work.

[GeoffR]

Originally Posted by Terisa de morgan

Yes, but scaled up doesn't equal bad quality. Anyway, the user has the two options, I only wanted to confirm that the option for upload covers was enough and it worked well.

You are reading kePubs, which are a bit different. The KePub reader will usually scale up the cover page to fill the screen even if the publisher has not done that in the stylesheet, so an undersize cover in a KePub is not such a big problem, it just results in lower image quality.

But with ePubs the cover is displayed at whatever size the publisher has set, which is sometimes too small because they have forgotton to specify a size relative to the screen size. In that case using the Kobo Reader output profile can result in an even smaller image size, not just a lower image quality. I think that is why the cover images in the OPs screenshot only occupy a small part of the screen.

[davidfor]

There has been a point missed.

For epubs, the cover image is created by rendering the first page. So, while the cover image size is important, just as important is how it is shown in the page. From the original screenshot, the cover images are just on the first page using an img tag. And there is nothing there to resize the image to fit the screen. Using calibre to add the cover will use an SVG wrapper to resize the cover image to fit the screen.

The other thing is that looking at the covers, they appear to be simple text covers with the title and author on them. It makes me think that somewhere along the line, the cover images have been generated from the text page and added to the book. I wouldn't be surprised if the books still had both. I'd probably look at removing those covers and letting the text cover stay and the device generating the cover image from that. Of course, you would need to make sure the text cover did size properly.

[Gogolo]

Thx! Exporting with tablet setting did the trick. Now 2k books to convert...

I wonder if conversion could not be archieved without converting the whole book. Is it not only a setting somewhere in a css style?

[GeoffR]

Originally Posted by Gogolo

Thx! Exporting with tablet setting did the trick. Now 2k books to convert...

I wonder if conversion could not be archieved without converting the whole book. Is it not only a setting somewhere in a css style?

Yes, the fact that changing the output profile caused the cover to change size on the page suggests that the books' stylesheets are not properly setting the image size. Probably all you need to do is change the image style to set the size using a percentage, so its size is relative to the size of the screen. The problem is that every publisher does things a little differently, makes slightly different mistakes, so it might take a lot of manual editing.

The two most common forms of cover page I've seen are roughly like these examples, but there are an infinite number of variations. Note the "100%" sizes to make the cover as big as will fit on the available screen.

Example using <img>

<html xmlns="http://www.w3.org/1999/xhtml">
<head>
  <title>Cover</title>
  <style type="text/css">@page {margin:0px;}</style>
</head>
<body style="margin:0px;">
  <div style="text-align:center;">
    <img style="height:100%;max-width:100%;" src="cover.jpg"/>
  </div>
</body>

Example using <svg>

<html xmlns="http://www.w3.org/1999/xhtml">
<head>
  <title>Cover</title>
  <style type="text/css">@page {margin:0px;}</style>
</head>
<body style="margin:0px;">
  <svg xmlns="http://www.w3.org/2000/svg"
       xmlns:xlink="http://www.w3.org 1999/xlink"
       width="100%" height="100%" version="1.1"
       viewBox="0 0 1080 1440" preserveAspectRatio="xMidYMid meet">
    <image width="1080" height="1440" xlink:href="cover.jpg"/>
  </svg>
</body>

[davidfor]

Originally Posted by Gogolo

Thx! Exporting with tablet setting did the trick. Now 2k books to convert...

I wonder if conversion could not be archieved without converting the whole book. Is it not only a setting somewhere in a css style?

You can use Polish books or the Modify ePub plugin to just change the cover page. Polish books inserts a page using the conversion code. It is the same cover inserted by a conversion. It's similar to GeoffR's SVG example, but the styles are different.

It's been to long since I used the Modify ePub plugin for this. I think it does the same, but I'd have to check.