image blurred with kindlegen, looks great in epub

[benbash]

I'm building an e-book for friends. Some have kindle devices, some use iBooks on an iPad.

The e-book is a reference document with a large map (6000 X 4200 pixels) done up in GIMP mostly black and white, with a blue river.
The map is saved as a 465KB .gif file.

I build the epub using pandoc and markdown as follows

pandoc -S --epub-metadata=metadata.xml -o guide.epub title.txt 01_intro.markdown 02_setting.markdown 03_rules.markdown

The map looks wonderful in epub on iBooks. I can zoom in on details, and pan out, exactly as I want.

For my friends with kindle, I then use
Amazon kindlegen(Linux) V2.9 build 0730-890adc2
like so:

~/Kindlegen/kindlegen  -c0 -gif  -verbose  -o guide.mobi  guide.epub

(I don't have a kindle yet, so I review the guide.mobi on the Kindle app on the iPad.)

On the Kindle app, the image looks blurred at high zoom. It looks like it has been compressed even though I have set the -c0 option for no compression. Some of the text on the map is unreadable.

I know it is working in the epub format.

Is there a better way to transform a working epub file to kindle format other than kindlegen?
Or do I have the syntax wrong for the creation of the mobi?
Or should I use a different image format, other than gif?

This post
https://www.mobileread.com/forums/sho...d.php?t=203580
implies the gif is over the 127KB max image size,
but this amazon kdp URL
https://kdp.amazon.com/help?topicId=A1B6GKJ79HC7AN
says
"The Kindle book format supports JPEG and GIF image files up to 5MB. "

Thanks for your suggestions.
Ben Bash

[benbash]

Hello. Does anyone have a suggestion on how to improve the quality of a large image for kindle (.MOBI) format?

Thank you,
Ben Bash

[DiapDealer]

You need to view the file on a device that supports the KF8 format (which should allow higher resolution images). When sideloading to an iPad, you're only seeing the mobi format (which doesn't support higher resolution images). Or ... the newest version of KindlePreviewer should allow you to produce an AZK file--which is specifically designed for sideloading to the Kindle app on an iOS device.

Your friends' Kindle devices would very likely be able to view the KF8 portion of the file you produced (rather than the lower quality MOBI portion).

[benbash]

Thank you for the response. I really appreciate it. I will check out KindlePreviewer and update this thread on how it goes.

Thank you,
Ben Bash

[Hitch]

Originally Posted by benbash

Thank you for the response. I really appreciate it. I will check out KindlePreviewer and update this thread on how it goes.

Thank you,
Ben Bash

Also, you should know that what's in the Kindle Publisher Guidelines has material that is ALSO intended solely for "real" publishers, by which I mean, companies that have publishing contracts directly with Amazon, like Random House, which FTP their ePUB books for subsequent conversion. It's companies like that, that can upload books larger than 50MB, and make use of the larger image sizes. Your image is being compressed, no matter WHAT setting you use in KG. (And, please note: will likely get compressed AGAIN, if the resulting mobi is uploaded via the KDP.) The 127gig limitation is, by and large, still in use.

To prove it to yourself, simply download the Preview mobi and use MOBIunpack to see the image file in the results. You're embedding that file wildly too large, by a factor of nearly ...lord, I can't even do the math this late at night. Reduce it, firstly, to at most 2560x1600 (use whichever dimension limiter suits you), and see what that gets you. That's the actual available rez for an HDX 8.9", and it will get you a lot of zoom-ability. Amazon adds to their dimensions the admonition to save the images "at a rez of 350ppi," even though the pixel-by-pixel dimension saving should put paid to that. Try that.

Trying an image that's 25mexapixels is just...too much. At least start by reducing the figures by half, and work down from there to get to a suitable resolution. You are, after all, trying to cram a 20" x 14" image (more or less) onto a very small screen, in the case of most readers. Going from 280 square inches of image to a screen that, on average, has 16.62" of square inch space is a pretty big cram. Like all images that are either enlarged far beyond their original pixels, or reduced in the other direction by the same amount, "images of text" will become heavily pixilated or fuzzy (also: if the text isn't anti-aliased, you'll run into issues there, as well).

Hope that helps. You can't expect the same type of image results from the iBooks app--which won't compress an image at all that's uploaded in an ePUB, to the results in a MOBI file, which ARE being compressed, and from your numbers, compressed quite a lot. You'll likely find you have to play with the image quite a bit, to get a result with which you are reasonably happy.

Hitch