This should do it. You may want to play with the -blur values. In IM -blur radiusxsigma, if you set radius=0, the radius will be determined automatically from the sigma. So I used -blur 0x5. But you can increase or decrease the sigma as desired. Also you can change the amount of white mixed with the background.
# first line -- read the image
# second line -- make a copy, blur it, resize it by width, crop the height so fits the screen size, colorize with white by 20%
# third line -- make a copy resize by height (so that width is less)
# fourth line -- delete the original and composite the resized image over the blurred image in the center.
convert 17cv28.jpg \
\( -clone 0 -blur 0x5 -resize 1920 -crop 1920x1080+0+0 +repage -fill white -colorize 20% \) \
\( -clone 0 -resize x1080 \) \
-delete 0 -gravity center -compose over -composite 17cv28_comp.jpg
http://www.fmwconcepts.com/misc_tests/r ... 8_comp.jpg
You may have an issue, if the aspect is much narrower. The command would need changing and you would need a test to check the aspect ratio of the image in comparison to the aspect ratio of the 1920x1080 display. But this gets you started.