Content How to download full resolution images?

[jhowell]

I am glad to hear that this idea is working out for you.

If I was going to do this I would add a step to check the accuracy of image matching between formats by finding an algorithm to determine image similarity and using it to automatically verify that the candidate substitutions are close matches.

[twynn92]

Originally Posted by twynn92

Also make sure the file extensions match too, but hopefully that will never be an issue since Amazon converts already anyways.

Aaand it's a good thing I did perform the check, as the third book I did had some GIFs in the KF8 which were converted to JPGs. I opted to keep the original GIF images, as (1) that doesn't require me to go into the text and mass replace .gif to .jpeg and (2) GIFs are lossless while JPGs are lossy. I'm not sure if that makes a difference since I'm sure Kindle-published books go through a conversion pipeline anyways. @jhowell Do you know anything about the GIF/JPG discrepancy between KF8/KFX?

The other thing to look out for is the cover image discrepancies. In other words, sometimes there are two references to two different images in the KF8, one being an IMAGE element within an SVG, and sometimes there are two references to the same image in the KFX, also duplicating the pattern of SVG/IMAGE tags and regular IMG tag. I think it's safe to (1) replace the cover image in cover_page.xhtml and (2) duplicate the same image in part0000.xhtml (if there is one) as there's precedent for that in the KFX source. Note that sometimes part0000.xhtml doesn't have a cover image and just starts with the frontmatter of the book, so keep an eye out to make sure there there are no unintended offsets.

Originally Posted by jhowell

If I was going to do this I would add a step to check the accuracy of image matching between formats by finding an algorithm to determine image similarity and using it to automatically verify that the candidate substitutions are close matches.

I didn't know there was such a thing, else I probably wouldn't have done so many manual checks via the single HTML text comparison as outputted by Pandoc. I mean aside from the cover image discrepancies, and the GIF vs. JPG difference, everything else is a one-to-one match, though the KFX code has too many necessary classes...

Thanks for giving me the opportunity to bounce ideas off of you. As you can tell, I'm no programmer, but do know bits and pieces to do just enough and get the intended output. This was more an exercise of curiosity than anything else, but good to know it's definitely possible with only one or two caveats.

[jhowell]

Originally Posted by twynn92

@jhowell Do you know anything about the GIF/JPG discrepancy between KF8/KFX?

I suspect that in those cases GIF is the original image format and that they are being converted to JPEG for KFX, but I do not know for certain.

Originally Posted by twynn92

Thanks for giving me the opportunity to bounce ideas off of you. As you can tell, I'm no programmer, but do know bits and pieces to do just enough and get the intended output. This was more an exercise of curiosity than anything else, but good to know it's definitely possible with only one or two caveats.

You're welcome. It is a topic that interests me.

[twynn92]

do we know if the KF8 downloads on Kindle For PC started having low-resolution images the moment KFX went live, so as to not waste storage space? Are there any devices/configurations that still use KF8 as the default format?

The second question is more for semantics than anything else, as I'd hate for my future book purchases to go less accessible at some future date, even if I've a local offline backup for current books. I assume that any configuration still using KF8 would be too small for high-resolution images to make any difference unless, of course, Kindles have some sort of magnification option for low-vision folks. I really should start considering moving to another book platform if EPUB compliance is something I care about, as I'm sure there is an obsolescence date for the KF8 format if not now, then some time in the far future.

[jhowell]

Originally Posted by twynn92

do we know if the KF8 downloads on Kindle For PC started having low-resolution images the moment KFX went live, so as to not waste storage space?

It is more a matter of higher resolution being supported on newer apps and devices over time. KF8 has a resolution limit for backward compatibility. That was later worked around by adding a separate AZW6 file for increased resolution of images. KFX is able to support the highest resolution. (AZW6 and KFX are both only delivered directly to devices that support them and are not available for download.)

Amazon delivers different packages of images tailored to different device types to save on bandwidth and storage. Amazon's current guideline for publishers is a width of 3200 pixels for a full page photo image in order to support viewing on high resolution tablets, but e-ink Kindles will actually receive much lower resolution images than that from Amazon.

Originally Posted by twynn92

Are there any devices/configurations that still use KF8 as the default format?

Older devices and apps. The third (2010) through fifth (2012) generation Kindles support KF8, but not KFX. Thankfully Amazon continues to support these with no sign of that ending.

KF8 is also the fallback format for books that are not available with Enhanced Typesetting, such as fixed-layout children's books.

Originally Posted by twynn92

I assume that any configuration still using KF8 would be too small for high-resolution images to make any difference unless, of course, Kindles have some sort of magnification option for low-vision folks.

Kindles have a pinch-zoom feature for images that allows more detail to be seen.

[JSWolf]

Can someone please post the instructions for downloading hi-res images instead of having to read this thread and then in the middle jump to another and then jump back? Thanks. It would be a lot easier this way.

[j.p.s]

Originally Posted by JSWolf

Can someone please post the instructions for downloading hi-res images instead of having to read this thread and then in the middle jump to another and then jump back? Thanks. It would be a lot easier this way.

Which other thread?

In any case, the only ways to get hi-res images from amazon are to OTA download a KFX with a kindle device or using K4[PC|MAC] then use the KFX calibre input plugin. The instructions for any of that do not belong in this thread. They are standalone tasks that need to be mastered, not read from instruction every time used.

[twynn92]

Originally Posted by jhowell

KF8 has a resolution limit for backward compatibility. That was later worked around by adding a separate AZW6 file for increased resolution of images.

Wait, so even Kindle for PC 1.17.x (last version before KFX was used) had low-resolution images embedded in the KF8 which was worked around via an AZW6 resource ancillary? So for Kindle Unpack, what's the difference with having the -i parameter versus without it? I doubt Kindle Unpack took into account the AZW6...

[jhowell]

Originally Posted by twynn92

Wait, so even Kindle for PC 1.17.x (last version before KFX was used) had low-resolution images embedded in the KF8 which was worked around via an AZW6 resource ancillary? So for Kindle Unpack, what's the difference with having the -i parameter versus without it? I doubt Kindle Unpack took into account the AZW6...

There are several variations of how Kindle books can be structured. When kindlegen creates a Master MOBI file it contains old MOBI and KF8 formats in the same file with a shared set of images. It can also have a CONT section with higher resolution images. The -i option will cause Kindleunpack to use the high resolution images from the CONT section instead of the lower resolution images.

Typically the KF8 section is delivered to reading devices an AZW3 file with low resolution images. The CONT section may also be delivered in a separate AZW6 file. Kindleunpack does not handle that situation and neither does calibre as far as I know.

I vaguely remember that there was a special situation where the combined KF8/CONT could be delivered by Amazon as a single file, but I'm not sure about that. If such files exist then the -i option of Kindleunpack will work with them also.

[j.p.s]

Originally Posted by jhowell

There are several variations of how Kindle books can be structured. When kindlegen creates a Master MOBI file it contains old MOBI and KF8 formats in the same file with a shared set of images. It can also have a CONT section with higher resolution images. The -i option will cause Kindleunpack to use the high resolution images from the CONT section instead of the lower resolution images.

Typically the KF8 section is delivered to reading devices an AZW3 file with low resolution images. The CONT section may also be delivered in a separate AZW6 file. Kindleunpack does not handle that situation and neither does calibre as far as I know.

I vaguely remember that there was a special situation where the combined KF8/CONT could be delivered by Amazon as a single file, but I'm not sure about that. If such files exist then the -i option of Kindleunpack will work with them also.

Is there some utility that will show whether a KF8 file has a cont section without unpacking it?

[jhowell]

Originally Posted by j.p.s

Is there some utility that will show whether a KF8 file has a cont section without unpacking it?

Nothing I am aware of.

[twynn92]

I was doing some stress-testing with large amounts of text, and as I figured bibles may have maps in them, searched for some free ones on the Kindle Store to kill two birds with one stone. Just to taunt me, when I downloaded one such free bible with cross references using Kindle for PC 1.24.3 , it came down as a combination of an AZW3 with an AZW6 resource ancillary. Note that its counterpart without cross-references came down as a standard KFX. I even double-checked that the AZw6 contained images by installing and invoking this patched version of the DeDRM which uses code from this Python script.

It is really too bad that there is no way for a user to force an AZW3/AZW6 download over its KFX counterpart, as this would have been the ideal solution. note that for both versions of the bible, enhanced typesetting is enabled, so assume that the only difference is that one has significantly more textual content than the other. If you disable the KFX renderer, i.e., renderer-test.exe on Windows, the AZW6 auxiliary resources do not download just as jhowell suspected. Note that for the AZW3 rendered by the renderer, the semantic information made available to Assistive Technologies such as screen readers still does not include the heading hierarchy even though there is such information in the XHTML source -- go figure...