.webp images not displayed on Kindle

[volkerwestphal]

Describe the bug While reading blogs on my Kindle I noticed that some images were not properly displayed. Instead of the image, a small placeholder (question mark) was shown. Other images were fine.

I found out that this affects images in the .webp format. They are properly displayed in the Calibre epub viewer, but not the Kindle device. Kindle device used: Kindle Paperwhite 11. Gen, Firmware 5.15.1.1

To Reproduce I have created and attached a very simple html file containing five different image formats.

Expected behavior Webp-based images should be shown as intended.

Desktop (please complete the following information):

• Version: v2.0.0-rc-1
• BuildDate: 2023-04-16T13:33:26Z
• Platform: windows/amd64

Additional context Kindle-send-testing.zip