Epub to mobi using KindleGen creates really low quality images – advice needed!

[Joefish]

My wife is about to self publish an eBook. It contains 60+ photos - mainly people and medical equipment. Most are 1200px wide and under 160KB in size.

I've so far built the epub file and everything looks good. I'm now trying to convert the epub to mobi format so we can sell it on the kindle store.

I initially tried using KindleGen as I read this was the best way to do it. I used kindleGens no compression mode - i.e. C:\KindleGen\kindlegen.exe -c0 C:\KindleGen\Book\my_ebook.epub.

After testing the mobi file it outputs on an older style e-ink Kindle reader (4th gen with the cursor pad), I discovered the images were very 'blocky' - backgrounds and skin textures are pixelated (Minecraft-style) or really blurry.

If you zoom in on the image, the quality seems to improve slightly. I've tried setting the image sizes (via html) to pixels and percentages and have also left the size attribute out. I still get blocky images. I tried reformatting the actual image files down to 400px wide to help avoid any resizing problems and again no improvement.

I then tried to use Calibre to do the conversion. And it improved things dramatically. No more blocky backgrounds or people!

So now I'm left wondering:

• Why does the KindleGen output such poor quality images even with compression turned off?
  
• Can I submit the mobi file Calibre made to the Kindle store, and if so, are there any problems/limitations I need to know about?
  
• How do professional publishers go about creating image-rich mobi files for the Kindle store?

[Doitsu]

Originally Posted by Joefish

Why does the KindleGen output such poor quality images even with compression turned off?

Because the built-in image converter does a lousy job and because the KindleGen compression options only affect text compression.

IIRC, there's an image resizing cutoff size somewhere between 64-128KB. If you resize your images yourself before compiling your book with KindleGen, KindleGen (usually) won't resize them again.
However, there doesn't seem to be any fixed number, because KindleGen sometimes won't touch a 120KB image but will resize a 100KB image in the same book.

You can down-convert your images to a specific size with ImageMagick (freeware command line tool).

For example:

convert -define jpeg:extent=128kb large.jpg small.jpg

BTW, you can find out how much KindleGen resizes your image by unpacking your mobi file with the KindleUnpack Calibre plugin or the standalone utility.

Originally Posted by Joefish

Can I submit the mobi file Calibre made to the Kindle store, and if so, are there any problems/limitations I need to know about?

Many self-publishers have successfully submitted Calibre-generated Kindle books, however, KDP has been known to occasionally reject Calibre-generated Kindle books.

[Joefish]

Thank you for the reply Doitsu. Very enlightening.

Originally Posted by Doitsu

Because the built-in image converter does a lousy job...there's an image resizing cutoff size somewhere between 64-128KB.

That's absolutely maddening. So even though Amazon suggest using massive images to cater for newer kindle devices, the official tool for creating mobi files borks images for older Kindle readers. Nifty!

I wonder if just uploading an epub2 to KDP and letting them handle the conversion achieves better results? I'm guessing not.

Originally Posted by Doitsu

BTW, you can find out how much KindleGen resizes your image by unpacking your mobi file with the KindleUnpack Calibre plugin

The kindleGen seems to be reducing my images from 160KB down to 60-70KB. Ouch!

What's even better, a test image I included in the book that was 40KB seems to have been left alone - the image size remains the same. However, It's obviously still doing something with it as it looks just as blocky as the other images.

KindleUnpack produces a folder called HDImages that contains my unmolested images. I'm guessing that on newer Kindle devices like the Fire my images at least look acceptable? Or is that just wishful thinking?

Originally Posted by Doitsu

Many self-publishers have successfully submitted Calibre-generated Kindle books, however, KDP has been known to occasionally reject Calibre-generated Kindle books.

I just read a few anecdotes suggesting the same. Doesn't seem like a reliable way to go about it.

So basically my options are:

• Use KindleGen and accept the fact my images will look rubbish on older e-ink readers and potentially newer kindle devices.
  
• Take my chances with the KDP online converter and have a teary when things look just as rubbish.
  
• Try uploading the Calibre mobi and watch the world burn

I never knew Amazon was this awesome

[Doitsu]

Originally Posted by Joefish

That's absolutely maddening. So even though Amazon suggest using massive images to cater for newer kindle devices, the official tool for creating mobi files borks images for older Kindle readers. Nifty!

Apparently, KindleGen does support larger images, but only for fixed layout books. For details, see this blog post.

Originally Posted by Joefish

I wonder if just uploading an epub2 to KDP and letting them handle the conversion achieves better results? I'm guessing not.

AFAIK, they also use KindleGen with some undocumented parameters. At least if you upload a KindleGen generated .mobi file (or an ePub file), KDP will have your original image source files. (KindleGen will attach the epub source files to the .mobi file, unless you use the -dont_append_source parameter.)

Originally Posted by Joefish

What's even better, a test image I included in the book that was 40KB seems to have been left alone - the image size remains the same. However, It's obviously still doing something with it as it looks just as blocky as the other images.

The converter might have problems with the image type that you're using. Can you post a typical image file and the resized file that you get when you unpack the .mobi file?

Originally Posted by Joefish

KindleUnpack produces a folder called HDImages that contains my unmolested images. I'm guessing that on newer Kindle devices like the Fire my images at least look acceptable? Or is that just wishful thinking?

I know that someone mentioned this folder in this subforum, but I'm a bit fuzzy about the details. I'm sure one of our resident Kindle/KDP experts will chime in on this.

Originally Posted by Joefish

So basically my options are:

Use KindleGen and accept the fact my images will look rubbish on older e-ink readers and potentially newer kindle devices.

IMHO, a better solution would be to experiment with different image formats and conversion settings. If you resize all images down to about 80KB with an acceptable quality, KindleGen might leave them alone.

[Joefish]

Hi Doitsu, thanks for another awesome reply.

Scots blog was a great read. Although my wife's book in non-fiction, I'd rather it wasn't fixed width. I'm a web designer by trade, so the thought of a non-responsive book makes me shudder. It's bad enough I'm having to deal with a proprietary file format!

I went ahead and uploaded the epub to KDP to see how their conversion handled the photos. As you hinted, the mobi they produced had the same overly compressed images. I guess their KindleGen is equally cr*p!

The photos are just standard JPEG, edited in Photoshop. Compiling the mobi with low-res images just to make it look OK in old e-ink Kindle readers would suck. It would effectively force others with newer devices or the Kindle App to also have a low-res experience.

I just noticed that any mobi file produced with the KindleGen is subject to a very restrictive terms of use - specifically, you can't sell the mobi file it produces outside of Amazon. Needless to say, we'll also be selling the book on our own website so this is yet another problem I wasn't expecting.

On a positive note, the mobi file produced by Calibre did upload to KDP without being rejected. When I downloaded the resulting file, it hadn't compressed the images. Yippee! The only curious thing was when I unpacked it using the KindleUnpack plugin - it contained the mobi7 folder and the HDImages folder but no mobi8 folder. Not sure why.

Given the restrictive nature of KindleGens terms of use, I think I'll persevere with Calibre. I should be ready to publish the book in the next week or two. When I do, I'll let you know how I get on.

Once again, thank you for all your sage guidance. You're a legend (and a wizard!)

[Doitsu]

Originally Posted by Joefish

On a positive note, the mobi file produced by Calibre did upload to KDP without being rejected. When I downloaded the resulting file, it hadn't compressed the images. Yippee! The only curious thing was when I unpacked it using the KindleUnpack plugin - it contained the mobi7 folder and the HDImages folder but no mobi8 folder. Not sure why.

Actually, there are two Kindle formats, that you can create with Calibre: the old MOBI format and the relatively new AZW3 format (AKA KF8). (If you convert to AZW3, you should get a mobi8 folder.)

BTW, KindleGen generates a hybrid book file that contains both old and new formats and the ePub source files. Depending on the capabilities of the device/app you'll either see the old MOBI format or the new AZW3 format.

[eschwartz]

I have heard that the main problem with uploading calibre-converted MOBI to the KDP is that it won't accept the newer AZW3 -- or dual-MOBI containing AZW3.

So effectively you are forcing all your readers to stick with MOBI (which has several disadvantages).



As for selling MOBI on your website -- you can just upload calibre-converted AZW3 on your website, or offer people EPUB and let them convert it.
As you've seen calibre does a darn fine job.




I believe the HDImages are only used by the Kindle Fires (and are stripped out of files delivered to an E-Ink device).
But you could double-check with KevinH at the KindleUnpack thread.

KindleUnpack will always extract them from the raw source (if available), and allow you to overwrite the actual mobi7/KF8 with the HDImages versions.
But that only helps someone who did the conversion on their computer, and wants to use KindleUnpack -- so it isn't a solution for selling on Amazon...

[Notjohn]

I have uploaded epubs to the KDP since January 2012, and I've never had such a problem. They convert just beautifully in my experience. I've never used KindleGen because I never could get it to work on my computer. I do have Kindle Preview installed, and I believe that's pretty much the same thing, but again, I've never used it to convert an epub because I like to get as close to the publishing process as I can, and THEN preview the book.

I build my epubs in Sigil, never in Calibre, though I often use Calibre for the opposite purpose (converting library epubs to mobi so I can read them on my Fire tablet). Calibre-generated CSS just scares me.

[Doitsu]

Originally Posted by Notjohn

I've never used KindleGen because I never could get it to work on my computer.

Shameless plug: There's a KindleGen plugin for Sigil 0.8.x that uses the KindleGen executable that comes with Kindle Previewer. If you've installed Kindle Previewer in the default folder, it should work out of the box.