Can we switch off alpha transparency for file thumbnails?

[kirk]

temporaril, rather off and on when necessary?

[Mario]

No.

[kirk]

It would be a nice feature.    Lots of my images are texture images for a game   where actual textures packed into all 4 RGBA channels. So sometimes I see no thumbnail preview at all in iMAtch  since the alpha channel is used for height/depth channel and it's often pretty dark.

Maybe it's possible to  rebuild thumbnails of certain chosen files without alpha for good?  Maybe ones within certain category or keyword?

[ubacher]

I would try to create a visible copy of the files (.jpg?) and make them a version. Then use visual proxies
to show for the "master" files. Then hide the versions. Imatch is flexible!

[Mario]

Maybe it's possible to  rebuild thumbnails of certain chosen files without alpha for good?  Maybe ones within certain category or keyword?

Nope, sorry.
The thumbnails in the database are created as PNG files when IMatch detects transparency or an alpha channel in the source file.
And the PNG files are always rendered with their alpha channel. There is no switch and I don't recall a similar request.

This is a rather special case and I think the solution proposed by ubacher above should do the trick for you. If this is important enough to maintain separate JPEG proxies for your files to see them without transparency.

[kirk]

It's a bit too much of a headache with special jpg proxi   . I wonder  could I just force imatch to use thumbnails from windows File explorer, I have "Mystic thumbnails"  utility   https://mysticcoder.net/mysticthumbs . It allows to build thumbnails ignoring alpha by choice.   Could Imatch  use 3d party thumbnails from Windows  ?

[Mario]

No. Thumbnails are stored in the database, IMatch creates them when it ingests your files.