jpeg artifact "removal", undoing the artifacts Options

[JohnVV]

first it is impossible undo the artifacts in jpeg images
now a lot can be done to synthetically "fix" them

information IS LOST in the jpg compression
yes it went into a black hole BUT the info was NOT conserved on the EH nor passed to a different dimension to be averaged out in the multiverse

-- it's gone --

A test image " Kodak's lenna " --- a industry standard used to calibrate equipment in labs
[attachment=25352:lenna.png]

the eyes and nose are good for showing results ( "g" rated ones )

( the below images are jpg's but , oh well . )
the orig. close up

a jpg artifact added ( two saves at 65% 2x2x2x2 )


over the years i have found a few things to do this NOTHING works very very well . However GREYCstoration now Gmic works well , within reason.
http://gmic.sourceforge.net/gimp.shtml

a gimp add on and a bash command line tool .
the gimp tool ONLY works on 8 bit / layer ( 24 bit rgb )
the command line tool works on 8,16 singed & unsinged ,and 32 bit floating point .

warning this only artificially fixes them

for now the gimp tool
i like the "edge preservation flow" pde

and the close up

the artifacts are gone BUT the image is way too smooth
add some noise

a small amount 4 will do

and the close up AND the orig. image


the terminal command

CODE

gmic 4.2.04b.jpg -gimp_edgepreserving_smoothing 0.8,0.5,0.6,2.5,50,10,0,0 -gimp_noise 4,0,0,0,0 -o clean.png

where "4.2.04b.jpg" is the input
and "clean.png" is the output

example from photojournal
PIA14673.jpg
left orig./ right "fix"

[JohnVV]

hi , maybe but the problem of jpg images is that the original data is already missing from the compression