Forma Can I safely delete the ".kobo-images" folder? It's taking 500MB of space.

[mathil]

Originally Posted by NiLuJe

@droopy: That's the settings yeah (i.e., on your screenshot, it's left to Nickel, calibre won't generate nor upload anything).

The Kobo Utilities plugin can re-process & re-send covers, but you'll want the patched version I linked to earlier, as the current release is missing some of the new options, which might lead to weird results.

FWIW, my own recommendation is to basically tick everything in there (i.e., Upload, B&W, Dither, PNG, Keep AR, Letterbox), but that's partly my personal preferences, so YMMV .

Thanks - I was looking for something like this just the other day in the hopes of saving some space on my device I've been substituting all of my covers using the plugin with greyscale ones: after this, will I have to do some clean up or it will be fine as is? And should I have it regenerate all thumbnails as well?

[NiLuJe]

@mathil: I'm not sure I understand your question (and/or what exactly you're currently doing. Which covers? Which plugin?) .

The filenames are fixed, and Calibre will always generate all three of them, no matter whether that's done by the device driver during a "Send To Device", or via Kobo Utilities (because Kobo Utilities will in fact just be calling the driver to do the work ).

If you meant: can you ask Kobo utilities to *delete* existing thumbnails, then I don't *think* so, but, again, that's basically the complete opposite of what I'm trying to achieve in my setups, so I wouldn't really know .
(Because, again, Nickel will be generating those after the fact anyway, and they'll quite possibly be larger that way).

[droopy]

Originally Posted by NiLuJe

Surprisingly enough it's for... the thumbnail images shown in the Library, Details & Sleep screens.

There's a few knobs in the Calibre Kobo driver to tweak how they're encoded which may help (very slightly) reduce their size, but some of those of those knobs may not have made it to the KoboUtilities plugin, yet, see this post.

In that bottom of your post,
you wrote

EDIT¹⁹: This is now included in Calibre >= 3.44.0 .

Since I'm using Calibre 4.1, do I still need to use your attached "Kobo Utilities.zip"?

[NiLuJe]

@droopy: The comment applies to the Calibre part of the changes. It has no bearing on plugins.

Until Kobo Utilities gets a new release, yes, you'll want the patched version if you want non-default settings.

[droopy]

Originally Posted by NiLuJe

Until Kobo Utilities gets a new release, yes, you'll want the patched version if you want non-default settings.

Thanks for your quick reply. Do you mean that with the non-patched version (the version that I do have), I can't just adjust the settings? Is your patched version required? What can your patched version do that the latest (non-patch) release can't do?

In my non-patched KoboUtilities version, I've already put a tick on all the boxes:

1. Keep cover aspect ratio
2. Upload black and white covers
3. Letterbox full-screen covers
4. Upload dithered covers
5. Save covers as PNG

[droopy]

I installed your KoboUtilities zip file but it still says that my Kobo Utilities plugin in Calibre is version 2.8.0. What should it read?

[NiLuJe]

@droopy: 2.8.0 . (That's on purpose, so you (and, more importantly, I ;p) won't miss the new release notification when it comes out).

Note that Kobo Utilities has its *own* version of those settings, it will not be using the drivers', which explains the need for a patch.

[droopy]

Originally Posted by NiLuJe

@droopy: 2.8.0 . (That's on purpose, so you (and, more importantly, I ;p) won't miss the new release notification when it comes out).

Note that Kobo Utilities has its *own* version of those settings, it will not be using the drivers', which explains the need for a patch.

Wouldn't having a version number like 2.8.0.1 make more sense? This way, it's clear that your patched version is different from the non-patched version. And secondly, it is such a small increment up, that more than likely, you and I won't miss the new-release notification, which will likely be bigger than 2.8.0.1.

I'm confused about Kobo Utilities using its own version of settings, and not the settings as found in the drivers'. Which drivers are we talking about? KoboTouchExtended and KoboTouch? Does it matter if the settings for Kobo Utlitiies is different from KoboTouchExtended?

[NiLuJe]

@droopy: Each of 'em has its own set of settings. Each honor their own settings. Whether you want them to all match is up to you.

Generally, that'd be true, but, if say, you want to try a different combination for a few books, Kobo Utilities having its own set of settings comes in handy.

[thp1017]

FWIW, I started deleting the files in .kobo-images that end with "N3_FULL.parsed" at some point when I was running out of space on one of my kobos... Those are are the full size image displayed on the first page, so I didn't see a need to keep them around after I've read the book... for a recent read, for example, the N3_FULL image was 670K (interestingly, the original was just 145K), where the size of the other two combined was 60K, so deleting just the one image makes a huge difference, without slowing down navigating through books/collections/etc. And that image *will* get regenerated down the road if the book is re-opened.

With that, my kobo-images folder is just ~100mb with something like 4400 books.

[droopy]

thanks for your helpful commment, thp. I plan to look into the N3-FULL.parsed files in the folder.

That reminds me, I have a CBR file (comic book) that would probably be much smaller if each page was grayscale.

[davidfor]

Most of this has been covered, but...

It is completely safe to delete the ".kobo-images" directory. It will be recreated when needed. The firmware will download covers for purchased books during the next sync and regenerated them for sideloaded books as needed.

As @NiLuJe, the KoboTouch driver can send cover images to the device when sending books. I'd completely forgotten that the plugin needed to be updated to use the new options. I have spend some time adding this today and have just released the updated firmware.

The driver and the utilities plugins options are separate, because the are separate things. And it is very likely, that you want to handle things differently when using them. For example, I usually have the cover sending options turned off in the KoboTouch driver, but have them turned on when using the KoboTouchExtended driver (because of how the covers are generated/extracted). These are set-and-forget. With the plugin, I can choose what I want to use at the time I am sending the covers to the device.

As has been mentioned, you can delete just some of the cover images. The device uses three. The smallest is used in the list and the middle sized one is used in the details page and on the home screen. The largest is used for the screensaver. You can remove any of these without affecting things to much. If you remove all of them, they will be regenerated the next time they are needed. This is done by regenerating the full size cover and then using that to generate the other images. But, if only the screensaver sized cover image is removed, it does not get regenerated. The next size down image is used instead. This will look terrible, but, it works and save space.

For this reason, I have also added an option to the remove covers function of the plugin to only remove the full sized cover. If you use this for all book you have read, or not planning to read soon, it will save space but not sacrifice the screensaver quality.

I do need to do some checking with this. I think if only the cover size used for the lists exists, that the others will be generated when needed. If that is correct, the others would save space as they would be generated when needed, but paging through the library would use the stored images.

I've considered for a while adding an option to the driver to send a smaller or lower quality image for the screensaver cover. I think I'd just use the 800x600 as that is the size used by the Touch. Or fiddle with the quality. This is set to 90, but could be reduced. I've no idea which would work better. I am not going to add more than one choice, just a "Save space by using smaller screensaver covers" option.

[droopy]

I have NiLuJe's patched KoboUtitilites Zip, and then my Calibre informed me that a version 2.9.0 of KoboUtilties is out, so I installed that 2.9.0 version.

Now what must I do to convert all the images on my Kobo Forma into grayscale?

Also, I have a comic-book ebook (CBR) file that is full-color. To save on space, how can I get just the grayscale version on my Kobo Forma?

[NiLuJe]

@droopy: From the Library view, select the books you want to update, Kobo Utilities > Upload covers for selected books

This'll pop up the KU popup with the same set of settings discussed earlier.

[droopy]

The one comic book I have is a 360MB CBR file.

I wanted to see if converting it into ePub would shrink the size.

Here are the steps I took
1. Choose "Convert Book" (in Ribbon or right-click context menu).
2. Choose "Comic Input" in the left side.
3. In the "Number of Colors" field, I saw the word "off". I changed it to "256", thinking that that is the maximum number of grayscale shades that a Kobo Forma can show.
(Am I mistaken? How many grayscale shades can a Forma show?)


The resulting epub was 60MB only! Wow, what a huge difference. One-sixth the original size!

UPDATE: When I changed the "Maximum colors" from "256" to "16", the file shrank even more ... to 26MB. That's about 1/13th the size of the original CBR. Loving it!