[Kusuri]

If you use the Kindle Comic Creator, you can put all images into a folder an then create a mobi / azw file with 100% width and height for the images. each image is a seperate page. normally i use this for mangas, but it works for all images that have the correct screen ratio format. Kindle Comic Converter is automatically stretching the image into the correct size.

After that you can use Calibre to edit the metadata (book name, autor etc).

p.s: there is also a method to do it with calibre somehow, but i tried that method for countless times and never got it to work correctly.. so Kindle Comic Creator was always the way to go for me. the only alternative i know other than that would be to create a pdf file with the images already 100% width & height and then using k2pdfopt to fix issues with the stretching of the images. but that takes A LOT more effort since you then also need to convert the pdf back to mobi / azw etc.. so i would just use KCC.