webp image handling

Turtle91 · 08-28-2022, 10:41 AM

Hi all -
More and more images online are provided in .webp format. Up 'till now I've just been converting them to .jpg (other than it is an 'optimized' format, I haven't researched the benefit of .webp yet).

This morning I added it to an ePub in Sigil. It imported easily and displays fine on the preview pane. However, when I ran the ePubCheck plugin it gave me an error: "A manifest fallback must be provided for image resource 'OEBPS/Images...' of type "image/webp". I have the image listed in the manifest with 'media-type="image/webp" ' (which Sigil did automatically).

Is webp (still?) a candidate format for the ePub spec or has it even been adopted in readers/apps???

Is there something else I need to do to make ePubCheck happy?

Cheers,

edit: ePubCheck also works in Calibre (I think) so this may be tangentially Sigil related.... If it would do better in the ePub forum could someone please move it?

Tex2002ans · 08-28-2022, 01:58 PM

Quote:

Originally Posted by Turtle91

Is webp (still?) a candidate format for the ePub spec or has it even been adopted in readers/apps???

It's been "allowed" in EPUB3 since 2020:

epub-specs: Issue #1344: "Add WebP as a core format"

but supported in many apps? Not really.

I wrote a bit about it the last time it was brought up:

2019: "What about webp images?"

Quote:

Originally Posted by Turtle91

More and more images online are provided in .webp format. Up 'till now I've just been converting them to .jpg (other than it is an 'optimized' format, I haven't researched the benefit of .webp yet).

It has some benefits (like smaller filesize + less ringing compared to JPG), but has slight downsides too (like much smoother).

Google pushed it incredibly hard, which is why much of the web has supported it.

But, in ebooks, for maximum support, it's still best to use good ol' JPG, PNG, (or GIF).

jhowell · 08-28-2022, 02:13 PM

I get the EpubCheck error of a fallback being needed for webp for EPUB 2 books, but not for EPUB 3. That makes sense to me.

KevinH · 08-28-2022, 03:29 PM

Support for it was added in the Epub 3.3 spec. Sigil already recognizes it. So any differences are either epub2 vs epub3 or are due to differences in versions of epubcheck.

Support added to Sigil in this commit in Sigil in Feb of 2021:
https://github.com/Sigil-Ebook/Sigil...192330f8f2f4cf

KevinH · 08-28-2022, 03:41 PM

And for what it is worth, the Epub 3.3 spec is still just a recommended draft and not final given this link:

https://www.w3.org/TR/epub-33/

So only web engine based readers probably handle it (if they are using a recent version). It is probably not supported on non-web engine based readers like RMSDK, etc.

So if you care about wide compatibility I would stick with jpg.

08-28-2022, 03:29 PM	#4
KevinH Sigil Developer Posts: 8,761 Karma: 5706256 Join Date: Nov 2009 Device: many	Support for it was added in the Epub 3.3 spec. Sigil already recognizes it. So any differences are either epub2 vs epub3 or are due to differences in versions of epubcheck. Support added to Sigil in this commit in Sigil in Feb of 2021: https://github.com/Sigil-Ebook/Sigil...192330f8f2f4cf Last edited by KevinH; 08-28-2022 at 03:33 PM.

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08-28-2022, 10:41 AM	#1
Turtle91 A Hairy Wizard Posts: 3,348 Karma: 20171571 Join Date: Dec 2012 Location: Charleston, SC today Device: iPhone 15/11/X/6/iPad 1,2,Air & Air Pro/Surface Pro/Kindle PW & Fire	webp image handling Hi all - More and more images online are provided in .webp format. Up 'till now I've just been converting them to .jpg (other than it is an 'optimized' format, I haven't researched the benefit of .webp yet). This morning I added it to an ePub in Sigil. It imported easily and displays fine on the preview pane. However, when I ran the ePubCheck plugin it gave me an error: "A manifest fallback must be provided for image resource 'OEBPS/Images...' of type "image/webp". I have the image listed in the manifest with 'media-type="image/webp" ' (which Sigil did automatically). Is webp (still?) a candidate format for the ePub spec or has it even been adopted in readers/apps??? Is there something else I need to do to make ePubCheck happy? Cheers, edit: ePubCheck also works in Calibre (I think) so this may be tangentially Sigil related.... If it would do better in the ePub forum could someone please move it?

08-28-2022, 02:13 PM	#3
jhowell Grand Sorcerer Posts: 7,070 Karma: 91577715 Join Date: Nov 2011 Location: Charlottesville, VA Device: Kindles	I get the EpubCheck error of a fallback being needed for webp for EPUB 2 books, but not for EPUB 3. That makes sense to me.

08-28-2022, 03:41 PM	#5
KevinH Sigil Developer Posts: 8,761 Karma: 5706256 Join Date: Nov 2009 Device: many	And for what it is worth, the Epub 3.3 spec is still just a recommended draft and not final given this link: https://www.w3.org/TR/epub-33/ So only web engine based readers probably handle it (if they are using a recent version). It is probably not supported on non-web engine based readers like RMSDK, etc. So if you care about wide compatibility I would stick with jpg.

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