BUG: ePub-to-PDF image output aspect ratios are distorted or broken

[lysakowski]

I frequently convert epub-to-pdf books, in order to preserve the fixed-page format and portability across time. I prefer to read the PDF as a 2-up on a wide screen, and once a year I might print a PDF. I need the fidelity of images to be preserved during the conversion.

The image aspect ratios of PDF output files are often broken or badly distorted, sometime so badly that they are totally unusable. I have not found any rhyme or consistent reason for why some images are badly distorted and others preserved well.

I have scoured the Calibre PDF output conversion interface and see no way to preserve converted images throughout the PDF output book. I see a way to preserve aspect ratio for the cover image only, but nothing else.

I looked in the v2023.06.0 User Manual and I see no command line option to freeze aspect ratio for PDF outputs.

Is there some setting or way to freeze the aspect ratio so that image fidelity is fixed for all epub images as they are moved over to the PDF file?

Can you provide an explanation for why and according to what rules that image aspect ratios are changed for static images?

Thank you.

Rich

[kovidgoyal]

It will depend on how the images are styled in the input document. If they are styled to expand to fill the page and the page size you are converting to is of a different aspect ratio than the image you will get stretched images, for example.