- launcher apps:
- lawnchair: 2.0-2589 : ch.deletescape.lawnchair.plah has that ability to hide apps. and
- trebuchet: 8.1.0.22 : com.lineageport.trebuchet can “protect” them behind system password too.
- they are sure foss, butttt it’s kinda complicated due to porting/availability situations (like @relan said here).
yeah, one more vote for old trebuchet (6.0.1.6 com.cyanogenport.trebuchet). those old launcher apps also had the awesome grid arrangement when rotated (in landscape orientation). no other launcher of today has that.
There are so many apps for that now, do they satisfy ur case??
medication | screenshot
wowww, glad this request came before as well. i made this as point one above 
that kind of capability is likely to be found in a file explorer app, have u tried that category of app? i havent yet, otherwise would have given a conclusive output.
check quoted post,
- app to make pdfs from images exist.
- remaining part is just to do perspective correction of images. or you can try to capture the documents as orthogonal as possible to avoid doing that correction in “post”.
- umh, the “grayscale filter” part will still be left, but i think lack of it doesnt block the task
plenty of apps nowadays for it
recipe
will this work? net.sourceforge.kid3 via audio tag
huff, took me 4 hours just to fly through all these… 
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