images don't display in converted mobi - Page 2

jhowell · 08-19-2021, 04:30 PM

I took a look at the JPEG images that are not rendering in the MOBI file. The ones that do not work all have no application segment following the start-of-image marker. Without that those images lack basic metadata such as resolution and aspect ratio.

JSWolf · 08-19-2021, 04:37 PM

Quote:

Originally Posted by xiatian

That's what confused me. Doesn't Kindle Paperwhite 3 support .azw3?

Yes, the PW3 does support KF8 (AZW3).

kovidgoyal · 08-19-2021, 08:42 PM

Quote:

Originally Posted by jhowell

I took a look at the JPEG images that are not rendering in the MOBI file. The ones that do not work all have no application segment following the start-of-image marker. Without that those images lack basic metadata such as resolution and aspect ratio.

AFAIK, those are optional in JPEG.

jhowell · 08-19-2021, 10:13 PM

Quote:

Originally Posted by kovidgoyal

AFAIK, those are optional in JPEG.

I agree, but the MOBI rendering software chokes if it is not present. As you wrote before it’s a bug, but I just wanted to document what triggers it.

I did some testing and found that kindlegen fixes this by adding JFIF metadata to JPEGs if it is not present in the source file, so that books published on Amazon do not exhibit this problem.

kovidgoyal · 08-20-2021, 02:08 AM

Well, it's easy enough to add JFIF by re-writing the image. This is obviously not ideal since it causes re-compression, but, given the Kindle bug I guess its worth it. https://github.com/kovidgoyal/calibr...1d5b0b37407393

jhowell · 08-20-2021, 09:29 AM

Quote:

Originally Posted by kovidgoyal;4147805[url

https://github.com/kovidgoyal/calibre/commit/9e2a7fca94c9b2f2c37937827f1d5b0b37407393[/url]

Thanks!

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08-19-2021, 04:30 PM	#16
jhowell Grand Sorcerer Posts: 7,072 Karma: 91577715 Join Date: Nov 2011 Location: Charlottesville, VA Device: Kindles	I took a look at the JPEG images that are not rendering in the MOBI file. The ones that do not work all have no application segment following the start-of-image marker. Without that those images lack basic metadata such as resolution and aspect ratio.

08-20-2021, 02:08 AM	#20
kovidgoyal creator of calibre Posts: 45,351 Karma: 27182818 Join Date: Oct 2006 Location: Mumbai, India Device: Various	Well, it's easy enough to add JFIF by re-writing the image. This is obviously not ideal since it causes re-compression, but, given the Kindle bug I guess its worth it. https://github.com/kovidgoyal/calibr...1d5b0b37407393

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