Thank you all for your responses.
@davidfor
Thanks for taking the time to provide such an extensive explanation. I learned a lot.
For a good understanding: I'm based in Belgium and bought my Glo at Fnac in Antwerp (a so-called FNAC-Book). It had a modified version of the firmware (version 1.9 or something). My computer OS is Linux, as is the OS of the Kobo. I "liberated" the Glo thanks to some instructions here on MR. This was a very fast, painless operation, completed without a hitch. Current version is 2.1.5 (r43939). I installed a few fonts of my own.
Re: Different cover images.
I noticed that the cover renders as good as can be expected in sleep modus. The library view is so small it hardly matters, but even so it seems to be all right. The problem is only with the cover view in reading modus.
On one hand I'm happy because there seems to be nothing wrong with my cover image. The problem is with the Kobo, and more specifically when it adds margins to the picture. This is confirmed by another experience I had. My book(s) contain full-page maps. When I just use the image-tag and add a "{text-align: center;}" class to the page, they appear smaller but sharper. When wrapped in svg-tags, sharpness is lost and they appear ragged, but bigger.
There are three possibilities, as far as I can see:
- The Kobo doesn't handle svg-tags well, or
- the Kobo borks the images by adding margins, or
- the Kobo borks the images by adding the extra "page"-margin
For the cover it doesn't help to omit svg-tags (let alone you then lose scalability which you need for display on other devices like tablets, iPads and mobile phones) because the Kobo forces the margins on the cover page.
Question: Is there a css code that could overrule the Kobo's page settings?
I have a few other remarks and questions which I will post separately at a later time.
Sorry to go on about this, but I like to offer my readers value for money, and I want my books to display as good as I can make them on as many devices as possible.
In this file I added the same map twice, once without and once with svg-tags (I adopted davidfor's version):