New version of HoneyView, starting with 5.23, now includes a preview handle for WebP files as well as PSD! And thus you can now preview them in Directory Opus!
http://www.bandisoft.com/honeyview/
HoneyView is one of my top favorite image viewers and now it's even better! I personally use it a lot to read mangas in CBZ/CBR format (supports image viewing from most archive formats).
Thanks for the recommendation, I am checking it out right now! Perhaps it will even replace the IrfanView for me (which is starting to get long in the tooth).
We'll be adding basic WebP viewer/thumbnail support in Opus 12.7.2 beta and 12.8.
Thank you so much, this is significant good news for me and my colleagues!
I installed 12.8 and WEBP support is there. Awesome.
Only missing thing (at least on my Windows 10 64bit) it's the ability to access the "convert image" feature with a right click on a WEBP file.
If i right click on any other image, i get the "convert image.." entry in the menu, if i do on a webp I don't.
Is there some setting to fix this? (Tools->convert image works as expected)
Settings > File Types > File Type Groups > Images
Add WebP to the list of extensions.
awesom, thanks!
Oooh a "hidden" feature, thanks!
This is great!
Though it seems that websites usually keep the .jpg extension in the filename, and then the plugin doesn't work on those in Opus. Unless I rename them manually by guessing that it must be webp.
The codec itself won't load those as it checks the extension of the file passed to it. We would have to rename the file to make it work.
(And websites that serve images as the wrong extension are stupid and really should stop doing that. :))
It works beautifly now. 
Thanks guys.
I have directory opus 12.10 installed, when I try to open a webp (which has a video clip embedded) I get a warning it is not a picture. When I try to open a vtx it opens, but the mouse wheel or page-up/page-down does not switch to the next previous in the viewer, as such for thumbnails of movies I'm stuck continuing with jpg files.
You'd normal use WebM for video, not WebP. Are you sure it is a WebP file?
I'm not familiar with VTX files (and there are at least three different file formats using that extension: https://fileinfo.com/extension/vtx ). Could you give more detail there? Is it even opening in the Opus viewer, rather than a third party viewer?
Yes, it is created with Video Tumbnail Maker and it does open successfully using the builtin browser.
http://www.videonizer-soft.com/downloads.html
The current version is 12 (and a trial can be downloaded), if you want to give it a try.
The program supports webm and webp, I tried webm as well, and it is not opened by directory Opus at all, while webp at least is attempted, but fails.
Can you upload a couple of the files (one of each type) that aren't displaying properly? (If you zip them up, the forum should accept them as attachments.)
BTW animated WebP isn't supported (at least currently), but I think we should at least show the first frame if the image is properly formed, although I'm not sure I've tested that as there weren't many animated WebP samples around when that code was added.
Here is the zip file with a jpg, vtx, webp and webm version (webp and webm include a 5 second video clip)
example.zip (10.5 MB)
Thanks!
The VTX file is byte-for-byte identical to the JPG file. So that's just a program which is using JPG under a different file extension, not a separate format. Opus recognises it as JPG.
I'm able to move to the next/previous image OK when viewing the VTX. Is that working for you with other file types, or not working in general?
Looks like we don't support animated WebP at all at the moment. Something we might add later.
Thanks for the update.
Thanks a lot for the webp format support. Would it be possible in the future to have additional support for thumbnails of archives, like we have with Jpeg? I have a lot of digital comics in cbz (aka zip) and it would help.
Done for 12.12.2.