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Old 08-10-2012, 11:23 AM   #1
scoobertron
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Kobo touch - what size for cover image?

I mainly read epubs, and wrote a little script to generate a cover image with the author and title details for books without covers. However, no matter what size I make the cover image, it is compressed horizontally with a white border to the left and right.

I have seen that this issue has been raised before in the forums, but I have not seen a solution for it. What size does the image need to be to fit the whole screen, or alternatively, how can I get rid of the borders?.

Incidentally, I am not using calibre for this, and don't really want to. The rest of the formatting in the epubs is ideal I prefer to manage my epubs myself rather than have a piece of software managing my library.
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Old 08-10-2012, 11:44 AM   #2
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I'm quite sure it is 600 x 800. You could try manually replacing the files in the \.kobo\images directory; I think you would want the "file name - N3_FULL.parsed" entry.
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Old 08-10-2012, 12:12 PM   #3
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The cover image is 800x600.

I resize my covers to 736 high, then add white border to the top to 800 pixels. This shows the entrire cover on the sleep screen, which the 'sleep mode' bar cutting into the cover image.
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Old 08-10-2012, 12:33 PM   #4
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Originally Posted by PeterT View Post
I'm quite sure it is 600 x 800. You could try manually replacing the files in the \.kobo\images directory; I think you would want the "file name - N3_FULL.parsed" entry.
Manually replacing the files in the .kobo/images direcory works. I needed to do a set for the list and grid views as well though.

Thanks
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Old 08-11-2012, 09:40 AM   #5
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For some reason a perfect image size doesn't make the image show full screen, despite whatever image size is mentioned in the titlepage.xhtml file (big sigh). Even removing the size tags or putting them to 100% doesn't work, I always get the side margins. It's so ridiculous!

There's one body code that works for the titlepage.xhtml, I'm afraid I can't remember who gave it to me here on the forum (sorry). But I used that code and Sigil changes it to the code blow. If you put that in the titlepage.xhtml file all will be perfect. But, yes, lots of hassle. Kobo should just use the image it's given instead of do weird things with perfect images.

Replacing the images in kobo's image directory also sounds like a good idea, I've never tried that. But also sounds like a hassle as you have to keep track of which books exactly you have to put the cover in for... and do it again if you add new books...

Code:
<?xml version="1.0" encoding="utf-8" standalone="no"?>
<!DOCTYPE html PUBLIC "-//W3C//DTD XHTML 1.1//EN"
  "http://www.w3.org/TR/xhtml11/DTD/xhtml11.dtd">

<html xmlns="http://www.w3.org/1999/xhtml">
<head>
  <title></title>
  <style type="text/css">
/*<![CDATA[*/

  body.sgc-1 {margin: 0px; text-align: center;}
  /*]]>*/
  </style>
</head>

<body class="sgc-1">
  <div><img alt="" src="../Images/cover.jpg" /></div>
</body>
</html>
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Old 08-11-2012, 05:08 PM   #6
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If you use Calibre I find that loading the book onto the Kobo, unplugging for processing, plugging back in and resending the book once, maybe twice, eliminates the white borders. Doesn't matter what the size of the cover image is. I have around 330 sideloaded books on my Kobo and the covers for all of them fill the entire screen because of this method.
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Old 08-11-2012, 11:18 PM   #7
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Quote:
Originally Posted by Canorka View Post
If you use Calibre I find that loading the book onto the Kobo, unplugging for processing, plugging back in and resending the book once, maybe twice, eliminates the white borders. Doesn't matter what the size of the cover image is. I have around 330 sideloaded books on my Kobo and the covers for all of them fill the entire screen because of this method.
Yes, that should work. I've been looking at the code for the driver, so here is an explanation.

With the current driver, calibre will upload four versions of the cover. They have the following suffixes in the names and sizes:

" - N3_LIBRARY_FULL.parsed" - 355*530
" - N3_LIBRARY_GRID.parsed" - 149*233
" - N3_LIBRARY_LIST.parsed" - 60*90
" - N3_FULL.parsed" - 600*800

But, it only uploads the covers if the Kobo Touch already knows about the book. This means you have to:

- Configure the driver in calibre to upload covers
- Put the book in the device
- Disconnect the device and let it process the book. The device adds the book to its database. With firmware 1.9.17 it also generated the above images in those sizes. With 2.0.0, it only generates the covers the first time it needs to display them.
- Reconnect the device and open calibre
- Use calibre to send the device again

Now we get to a difference between the firmwares. For 1.9.17, the device creates and use all four of the above images. From memory, the "N3_FULL.parsed" version is used when the device sleeps. For 2.0.0, only the first three are create. And it uses "N3_LIBRARY_FULL.parsed" when sleeping. I'm not sure if it is displaying this image centred on the screen, or stretching it. I can't quickly find a cover that would prove it one way or the other the other.

As it happens, I did an experiment with this yesterday. I renamed one of the N3_FULL.parsed images to N3_LIBRARY_FULL.parsed. So, I had a 600*800 image in place of the 355*530 image. The device used this with no problems and it filled the screen when it was sleeping.
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Old 08-11-2012, 11:28 PM   #8
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Yes, the 6-inch Pearl e-ink screen is SVGA, 800x600 px, 16 level grayscale.
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Old 08-12-2012, 07:09 AM   #9
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Davidfor, thanks for the interesting explanation. Could you elaborate a bit on how resending the books from calibre after the device processes could cause the device to use a different version of the cover? And, If you resend a book, do you delete it from the device first?

I'm not sure I understand correctly if this resending method would work for FW 2.0.x...
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Old 08-12-2012, 08:19 AM   #10
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OK Mrs_Often, just remember that you asked

Quote:
Originally Posted by Mrs_Often View Post
Davidfor, thanks for the interesting explanation. Could you elaborate a bit on how resending the books from calibre after the device processes could cause the device to use a different version of the cover? And, If you resend a book, do you delete it from the device first?
When the Kobo Touch and I think other Kobo ereaders are disconnected from the USB, they scan the all the books on the device. If the book hasn't been seen before, it is added to its database. Here "seen before" simply means that it isn't in the database. The device does a lot of work when it finds a new book. It will:

- Create a record for the book. This contains the location of the book and some of the metadata. The record is also used to record the state of the book including whether it has been read and how far through you are. It also has details of the type of book or if it is a preview and downloaded. And it has the "ImageID" the device uses to for the cover of the book.

- For each chapter in the table of contents, creates a record in two different tables. This is used to build the TOC when you are reading.

- Generates the cover images (for firmware 1.9.17 and earlier).

This processing is why there can be problems when the device processes new books. The error handling for badly constructed books means that it hangs, reboots or simply stops processing with the broken book.

Now resending a book (yes, I am finally getting to your question) means simply selecting a book that is already on the device in calibre and pressing the "send to device" button. Calibre will simply put a new copy of the book on the device in place of the one that was there. If you have the option to upload the covers, calibre will generate covers and copy them over. Calibre uses the existence of the ImageID I mentioned above to decide it can do this and to name the files. These covers will replace the ones the device generated and will be used in the devices book lists and for the sleep screen.

You can also send a new copy of the book if you have made changes to it. But, firmware 1.9.17, doesn't reprocess it. If you change the metadata or the TOC, the changes don't get picked up and added to the devices database. Generally, this is OK, but if the structure of the file changes, it can cause the device to restart when you try to read the book.

The exception to the above is if you change the title or the authors. These are used in the file names of the books on the device. The device will see the file as a new book.

If you delete the book from the device using calibre, it cleans up the database and file system. All the records related to the book in the device database are deleted, the covers are deleted, the book file is deleted and the directory the book is in is deleted if it is empty. If you send the book to the device after this, the device will see it as a new book when you disconnect.

Quote:
I'm not sure I understand correctly if this resending method would work for FW 2.0.x...
Now, for FW 2.0.x, it works mostly the same. The current Kobo driver in calibre handles the books and covers in a way that the Kobo device is fine with. The device doesn't generate the cover images immediately, but everything else is the same. Almost.

The "almost" is because FW 2.0.x does do some processing of the new version of a book. It doesn't recreate the cover images or change the stored metadata and TOC, but it can decide to completely remove the book. This happens for some changes to the book. Unfortunately, I haven't been able to determine exactly what changes it cause this. I have replaced books with extra chapters (downloaded as the author writes them) and changed CSS and they haven't been deleted. But, changing the title did cause the book to be deleted.

FW 2.0.2 seems to be a little less critical than 2.0.0. I had a lot more books disappear after updating them while I had 2.0.0 than I do with 2.0.2.

Still here? I think that is it. That is probably a lot more than you wanted to know, but there it is.

I better add a disclaimer: The behaviour I describe above for the Kobo Touch is based on my observations. I've done a bit of experimentation to see what happens and had a good look at the database and file structure. The calibre behaviour is again my observations plus looking at the code. Any of this might be wrong. If anyone sees something wrong, please correct me.
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Old 08-12-2012, 11:04 AM   #11
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Wow, thanks Davidfor!

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OK Mrs_Often, just remember that you asked
I do, and I'm glad I did!

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Still here? I think that is it. That is probably a lot more than you wanted to know, but there it is.
Yep, nope, the exact amount I wanted to know. I like to understand how things work. Thanks. Will save me a LOT of messing about with changing cover sizes and manually editing all the titlepage.xhtml files.

I still find it strange though, that the first images the KT genereates for a new book don't just properly fill the screen in sleep mode (or in the thumbnails). Stupidness.
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Old 08-12-2012, 08:00 PM   #12
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Yep, nope, the exact amount I wanted to know. I like to understand how things work. Thanks. Will save me a LOT of messing about with changing cover sizes and manually editing all the titlepage.xhtml files.
I'm glad it helps. In any case, that sort of post also helps. The act of writing the always clarifies my thoughts and prompts me to check a few things.

Quote:
I still find it strange though, that the first images the KT genereates for a new book don't just properly fill the screen in sleep mode (or in the thumbnails). Stupidness.
There are two reasons I can think of. Space is one. With 2.0.0 they are not generating the largest cover image, so the cover images won't take as much space. The other thing the total number of images. They are only generating up to three instead of four. That keeps the total number of files in he images directory down and could prevent some problems.
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Old 08-14-2012, 04:47 AM   #13
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If you are still interested you can take a look at this post. I'd be interested in your script if you can share it.
Thanks
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Old 08-14-2012, 06:08 PM   #14
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dsandrei:

Script is here:

http://tinyurl.com/cky2ojr

I have added some comments and some variables so people can adapt it for their own use. It should go without saying that people shouldn't run it without checking it for themselves as it was written purely for my own use and is probably quite rubbish and may break everything (and apologies in advance to anyone who can actually code and is offended by my hackery).
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Old 08-14-2012, 08:16 PM   #15
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dsandrei:

Script is here:

http://tinyurl.com/cky2ojr
Sorry, but that's bad. You generate one 600*800 image and then use it for all five images that the Touch generates. That is a big waste of space. And there would be a performance hit on the Touch each time these images are used. The N3_FULL is used for the sleep screen The others are used when browsing the library. Each time they are displayed, they will have to be dynamically resized. That will slow things down and if you have lot of books, it is already getting slower. I listed the sizes for all except on of the images above. I missed "N3_LIBRARY_SHELF.parsed" which is 40*60.

Also, the script is for pre 2.0.0 firmware. The touch only generates three cover sizes in 2.0.0 and later.
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