Yesterday, I received a Kindle Paperwhite Signature Edition as a gift, model: M2L4EK

It’s a beautiful device with a big and easy to read screen, certainly a big upgrade from my Kindle Keyboard 3G. Only, it doesn’t support EPUB, which my Keyboard 3G does, by means of Duokan. So I just converted Marina Abramović’s Walk Through Walls to AZW3 using Calibre 6.13 on Windows 10 Pro. As input profile I tried Kindle and Default, and as output profile I select Kindle Oasis because - per description - this is intended also for the Paperwhite 2021.

Unfortunately, the images are vertically stretched. It looks like there are two types of images. Some are stretched to fill the entire page, some half the page, minus caption. This issue does not exist in the original EPUB, and I could read the book just fine using Duokan.

Is there an easy fix?

(I wish there was a jailbreak for the device with a decent EPUB and PDF reader, or a dual boot solution with Duokan like for the Keyboard 3G.)
https://www.mobileread.com/forums/sh...d.php?t=186697
OK, so I extracted the first chapter. Then I lorem ipsumized the text using the Chrome plugin LoremIpsumReplacer, and I pixelated the images using ImageMagick, only to find out:

The issue happens with AZW3, but not with MOBI.

Find the modded file attached. Seems like I damaged the meta data or something. There is an error, but it doesn’t influence conversion. The pixels in the images should be squared. With the AZW3 in many images they are distorted.

I am happy to provide more info, but for me the issue seems to be solved. I simply convert from EPUB to MOBI instead of to AZW3.
You actually want Input profile to be Default profile and Output profile to be Tablet. That way the images are not changed at all. With your current settings, images are modified.
I tried, and with input Default and output Tablet, I get the same issue in the AZW3 file. Note that the images are not uniformly stretched by a factor. Instead they seem to be stretched either to fill 50% of the height or 100%, minus caption.
The markup in that file is causing the distortion, since it hardocdes widths for the images. AZW3 supports such markup MOBI does not.
Thanks for looking into it. What fix do you recommend?

(MOBI looks fine to me, so maybe I don't even need a fix.)
Post a the section of the html code that displays the images and any relevent CSS code. We can take a look. It would be good to know what's going on if you want to fix a similar issue in the future.
You would need to remove the width attribute from all img tags which can be done via the Transform HTLM tab of the Look & feel section of the conversion dialog.
Thanks for the suggestion. Here is an example of an image that gets heavily stretched vertically across an entire page, minus caption (code reformatted by me):

What I tried as transformation rule:
image »

However, all that this does is create two equally stretched images. First, I tried just removing width, and when that didn't work, I just remove pretty much everything.

(note that I'm fine exporting to mobi, but I'm also happy to continue testing Calibre in case that helps)