Bug 485150

Created attachment 168231 [details]
Zip file containing 2 images showing the error message in Gwentview. One is a PNG directly from Spectacle, the other is the PNG converted to JPEG by imagemagik

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SUMMARY
Spectacle screenshots in jpeg or webp format (and others) are consistently saved with the mime type "image/_Common Types". Gwentview can not open the files.

STEPS TO REPRODUCE
1. Open Spectacle app
2. Click Configure
3. Click Defaults
4. Capture a screenshot with: Rectangular Region, All Screens, Current Screen, Active Window, or Window under Cursor 
5. Click Save

OBSERVED RESULT
Dolphin displays the resulting png file type as "image/_Common Types". Gwentview fails to open the screenshots and displays the following error where [fileName] is the default file name generated by spectacle:

"Loading ‘[fileName].webp’ failed
"Gwenview cannot display documents of type image/_Common Types."

EXPECTED RESULT
Dolphin shows the png file type as "PNG image" and gwentview opens the image without any errors.

SOFTWARE/OS VERSIONS
Windows: 
macOS: 
Linux/KDE Plasma: Fully updated Manjaro X11 Distribution with Kernel 6.6.19-1-MANJARO (64-bit)
(available in About System)
KDE Plasma Version: 5.27.11
KDE Frameworks Version: 5.115.0
Qt Version: 5.15.12


ADDITIONAL INFORMATION

Testing on Newer Versions: I did not find a newer version of Spectacle through the Pamac GUI (with snap and flatpack enabled). I did not find Spectacle at all on Flathub. Spectacle 23.08.5 is the current official Manjaro version.

Problem Started: A few days ago, perhaps when I updated my apps after the xz exploit surfaced (I have, very rarely, encountered a red error in thep ast in Gwentview. They can usually be respoved by opening and exporting through GIMP, though sometimes GIMP can't open them either. I suspect that those were unrelated, but I can't recall the source of those files or the particular error messages).

Frequency: Every TIme

File formats and Mime Types:
webp, jpeg, png, tga: have the "image/_Common Types" mime type
bmp, tiff: have the expected mime types
other types: not tested

Actual file format: Files are otherwise as expected. I can open and convert/export them with ImageMagic and GIMP. Converted and exported files have the correct mime type regardless of file format chosen, and open in gwentview.

Does "image/_Common Types" Exist?
I didn't find any evidence of it - Googling the quoted string "image/_Common Types" returns less than a full page of results and suggests "image/Common Types" which returns about 10k results. Neither search returns front page results that include the quoted search string. Both return images at the top of the results, but none of the images are of the quoted mime types. I did not find anything starting with "image/_" or "image/co" (case insensitive) on mime type lists hosted by: mozilla.org, mimetype.io, freeformatter.com, or digipress.org.