Quote:
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?
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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).