I’ve been using lossless webp images frequently to store my digital art, because of the quick encoding times and consistent size improvement over png (even png files sent through pngout, optipng, and deflopt). It’s been useful to use Google’s official webp codec so that webp thumbnails appear correctly in Windows explorer, and webp files can be seen in photo viewer.
Everything worked perfectly in Windows 8.1, but in Windows 10, in Windows Photo Viewer, I noticed that .webp images were being shown incorrectly. They were too dark.
The user “DH” on the techdows blog had a fix that worked for me, and I’d like to share it more publicly.
(Posted by DH, 2019-07-02)
If the google webp codec is installed, uninstall it.
Open cmd as Admin (or open Powershell as admin and skip next step)
Type: powershell
Type: Get-AppxPackage *Microsoft.WebpImageExtension* | Remove-AppxPackage
Test by trying to open a webp image in Windows Photo Viewer. It should fail.
Ignore the thumbnail image if it is there, as this was generated
beforehand. Now install Google’s webp codec (follow the link in the post).
Open the webp image with Windows Photo Viewer again. This worked for me.
Not only did it fix the darkening issue, but it loaded the image much
faster.
The original comment is here. As a side note, this article on howtogeek describes how to use Photo Viewer as default instead of the Photos app in Windows 10. Anyways, hope this helps!