Aura HD Images: possible to double the size?

[dietrannies]

Hey all,

I know alot of similar things have already been discussed, but I haven't been able to find a solution to my problem yet.

To help me with my studies I bought a coursebook through the Kobo store (Adobe DRM format). Now, as long as it's plain text, it's all good, but as soon as images and mathematical equations are shown, they're just way too small. I assume because these were made for lower res devices, and now they show up on the Aura all tiny and unreadable. This annoys me, for one, because I bought it through the shop, for 70 freaking euros I might add, and I somehow made the wrong assumption I'd actually be able to read and use the entire thing.

Is there any solution at all to this? It doesn't even have to be easy, and I wouldn't mind some tedious conversion process through Calibre or something, cause I see myself using this book as a reference for years to come.

Thanks in advance!
D

[GeoffR]

You bought the book from Kobo, are you using the kepub version downloaded directly to the device or the standard epub version sideloaded? Whichever one you are using you might want to try the other, just to see if it makes a difference.

If not then the first thing I would do is let Kobo know about the problem with the book, and say that you want a refund if they can't fix it. (Or rather, if they can't get the publisher to fix it.)

While you can probably fix the book yourself, it could take a lot of manual editing, many hours of work possibly, to fix things the publisher has done wrong.

I fix fiction books which just have a couple of full-page images which display too small. That takes 5 or 10 minutes usually, but they are usually simple cases where there is just the image on the page, no text, and my goal is just to get the image to display as large as possible. If there are images embedded in the text I expect it would take more work, and probably more knowledge of html/css that I have so far.

Although the equations are too small, do they change in size at all when you adjust the font size? If they stay the same size regardless of font size then they are probably just small bitmap images rather than scalable vector graphics, and it might be difficult to get them to look good at a larger size anyway. If they do change in size then it might be fairly easy to fix just by editing the CSS stylesheet, depending on how the book is layed out.

Sorry for the negativity, I hope someone else will have some suggestions. 70 euro is a lot to pay for a book that doesn't work properly.

[filmo]

Pinch zoom might help solve this problem of small unreadable text in pictures and equations. New 6 inch Kobo Aura has pinch zoom. Sony T1, T2, and soon to be released T3 has Pinch zoom. Kobo could have pinch zoom for your HD Aura in future firmware or not. We just have to wait and see. The open source programmers at Kobo Developer's Corner might have something that would help with their Koreader program for Kobo eink readers. Pinch zoom can not show picture details that is not in a low resolution jpeg picture displayed on your reader so it might not help.

https://www.mobileread.com/forums/forumdisplay.php?f=247

[PeterT]

Also remember we're not at all sure whether pinch-zoom will be available on ePubs or solely in kEpun format.

[GeoffR]

Here is an example of a problem in one of my books that might be similar to the problem with your small equations. The text has a word in cyrillic script, but instead of doing it the proper way and embedding a subset of the appropriate font, the publisher instead just embedded a tiny bitmap image of the word:

<p>... a stack of boxes marked <img alt="image" src="images/Art_P104.jpg"/>, smiled.</p>

As it is, the bitmap will not change size when the font size changes, so it will only look OK at one particular (tiny) font setting, which might be the default font on an old low resolution device.

By adding a relative height (style="height:1em;") to the code above I can get the image to change to match the font size of the surrounding text, which fixes one problem, but it still looks awful because the original bitmap is of such low resolution.

[glos]

About this problem with images, there was this topic here
https://www.mobileread.com/forums/sho...d.php?t=211923
that I've read, but I don't completely understand what I have to do in Sigil to make an image appear with its real size instead of super-small how I see it on my Kobo.

DNSB suggested this code for the Glo

<div>
    <svg xmlns="http://www.w3.org/2000/svg" height="100%" preserveAspectRatio="xMidYMid meet" version="1.1" viewBox="0 0 660 880" width="100%" xmlns:xlink="http://www.w3.org/1999/xlink">
      <image height="880" width="660" xlink:href="../Images/cover.jpg"></image>
    </svg>
  </div>

is it correct, then, if I do this?
supposing I have this:

<p><img alt="anoptic_carshare" longdesc="http://farm9.staticflickr.com/8304/7766508504_92dd553a77.jpg" src="../Images/ffdl-2.jpg" /></p>

where my image is in fact 500x492px

I should delete that code and substitute with this one

<div>
    <svg xmlns="http://www.w3.org/2000/svg" height="100%" preserveAspectRatio="xMidYMid meet" version="1.1" viewBox="0 0 500 492" width="100%" xmlns:xlink="http://www.w3.org/1999/xlink">
      <image height="492" width="500" xlink:href="../Images/ffdl-2.jpg"></image>
    </svg>
  </div>

right?

I've tried just now with 2 images and it seems to be working, they're now much bigger and I can read what's written on them, though they're slightly pixelated, but I guess that's normal... anyway it's good enough for me

[dietrannies]

The book was bought and downloaded directly through the shop on the Kobo itself. When I went through the library on the kobo books site, it said the format was Adobe DRM epub. I got to download it through there and then in Adobe Digital Editions and in Calibre I unpacked it and got a look at the image files. Used a batch resizer program to make them all double size, repacked the epub, and put it on the device. Well at least everything's legible now, but now all the fancy official functions like the contents are all gone. Which is again pretty silly for a reference book. Now I get to choose between having that, or actually being able to read graphs and formulas.

It seems like the Aura HD has this with images in general though. I've seen it in sideloaded epubs as well, where the images are supersmall. Looks like every time I get an epub with images, I'll have to sort all this out the hard way.

I'm very new to kobo, and I see you all posting code and all that. Are there hacks or mods or something for these devices that could solve this?

[DNSB]

Originally Posted by dietrannies

It seems like the Aura HD has this with images in general though. I've seen it in sideloaded epubs as well, where the images are supersmall. Looks like every time I get an epub with images, I'll have to sort all this out the hard way.

I'm very new to kobo, and I see you all posting code and all that. Are there hacks or mods or something for these devices that could solve this?

What worked for me is displaying images using the SVG wrapper technique. Basically, you can make the image fit a page so if the display resolution increases, the image is automagically zoomed. This is useful for maps, illustrations, etc. where you want a large image. For decorative elements such as fleurons and vignettes, stick with the standard image insertion.

One item to remember with the SVG wrapper is that the numbers are not actually the image size as no units are specified. They represent the aspect ratio of the image and the viewbox.

Regards,
David

[GeoffR]

Originally Posted by dietrannies

It seems like the Aura HD has this with images in general though. I've seen it in sideloaded epubs as well, where the images are supersmall. Looks like every time I get an epub with images, I'll have to sort all this out the hard way.

I'm very new to kobo, and I see you all posting code and all that. Are there hacks or mods or something for these devices that could solve this?

It is possible for publishers to create their epub books so that they will work properly on devices with different screen sizes, unfortunately most can't seem to be bothered. I don't think there is one method that would work to fix all the problems, because each publisher seems to get in wrong in different ways.

As I see it there are basically two ways images are used in a book:

1. As fixed display images which should be sized relative to the size of the device's screen (or the display window on windowed systems). E.g. Cover image, maps, large interior artwork, etc.

2. Images that are part of the text which should be sized relative to the size of the other text elements, and should change size when the reader changes font size. E.g. fancy chapter headings, scene break symbols, mathematical equations, elvish runes, etc.

To look good on all devices the images need to be able to scale to suit the device with the largest/highest resolution screen. This means they should either be scalable vector graphics images, or alternatively, bitmaps of sufficient resolution to suit the device with the highest resolution screen.

In some cases you can just replace the small bitmap images in the epub with larger ones and everything will work OK, at least on one device. This depends on the type of display code the publisher has used. It probably won't work for images which are supposed to resize with the text.

Other cases the image resolution is OK but the publisher has used absolute instead of relative sizes (or failed to specify a relative size where the default is absolute) in the display code, so the image won't change size to suit different devices or font sizes. In this case you can change the display code to use relative sizes (e.g. "100%" for display images, "1.00em" for textual elements). But I doubt this can be done automatically, because it requires some judgement about what the image should be sized relative to.

If both problems are present you can use SVG display code to scale up the bitmaps to any size you want, but the results will depend on the quality of the original bitmap, it is unlikely to look as good as a proper scalable vector graphics image.

I have noticed that with some books the kepub version downloaded direct from Kobo to the device has much higher resolution images than the standard Adobe DRM epub version that you can download from the Kobo websize. Also you can sometimes get higher quality images for the book fom the publisher's website. (although usually it is just the cover rather than the interior images).

[paola]

I wonder whether an easier solution than opening up your book might be to add the line below to the "Kobo_eReader.conf" file located in the directory .kobo\Kobo\Kobo_eReader.conf in your reader. It is a text file, so you can edit it with any text editor. Here is the line you have to add:

ImageZoom=true

To see what it can do to an epub page with images, see the screenshots in post 23 here

[PeterT]

Originally Posted by paola

I wonder whether an easier solution than opening up your book might be to add the line below to the "Kobo_eReader.conf" file located in the directory .kobo\Kobo\Kobo_eReader.conf in your reader. It is a text file, so you can edit it with any text editor. Here is the line you have to add:

ImageZoom=true

To see what it can do to an epub page with images, see the screenshots in post 23 here

Some caveats: It's actually

[FeatureSettings]
ImageZoom=true

Originally Posted by uboot

Thanks! I configured my reader such that the menu will not pop up on center tap, but bottom center tap.

Anyways - I did some more research and it appears to me that:

1.) Image Zoom only works for kepubs
2.) The Image Zoom button _only_ appears if there is a _full screen image_ on the page. It does not show on text pages or on pages containing both - text and images. That's why I thought it didn't work at all...


PS: any ideas on my other question (additional games)?

[paola]

Originally Posted by PeterT

Some caveats: It's actually

[FeatureSettings]
ImageZoom=true

thanks Peter, I did not know

[FeatureSettings]

was necessary (though I used it in my file).

[CmplxAdSys]

Sorry to resurrect and old thread, but I'm having similar trouble with my Kobo Aura H20 and a math-heavy e-book I purchased from kobo. The book has a separate CSS, so I edited the CSS for the equations in Calibre.

Unfortunately, the 1em trick doesn't work, nor does trying to scale by percentages (the buffer increases, pushing the text, but the image remains the same tiny size). The svg wrapper technique may work (didn't try it) but I'd prefer to just edit the CSS versus wrapping each image (one of hundreds!) in the wrapper provided.

Any idea on how to port the svg technique to CSS? I'm not skilled enough to quite know how to do it on my own.

Alternatively, has anyone come up with any ideas on how to fix this problem besides those mentioned above?

Thanks in advance!

[GeoffR]

Here is a recent thread on the issue: https://www.mobileread.com/forums/sho...d.php?t=265355

It all depends on how the publisher has done the css and html, in some cases you might find it easier to just resize the images themselves with tools such as ImageMagick, in other cases you can just edit the css, but in some cases there might be no option but to go through and edit each individual html tag.

If you could post an example of how a typical image is referenced from the html, along with the relevant css styles, then someone might be able to suggest the easiest way to do it.

Edit: AFAIK there is no way to do SVG just from CSS alone, you need to have a SVG wrapper for each individual image if there isn't one already.

[rashkae]

If the book is a kepub, (either auto synced from Kobo, or sideloaded with Calibre and the Extended Kobo Driver plugin.), then you can double tap on images to open them in an "Image viewer" That will scale them up to the size of the screen, and allow you to zoom and pan as well.