proc medianfilter {image} {
set w [image width $image]
set h [image height $image]
#-- read graylevels of image into list of lists matrix
set data {}
for {set i 0} {$i<$h} {incr i} {
set row {}
for {set j 0} {$j<$w} {incr j} {
lappend row [lindex [$image get $j $i] 0]
}
lappend data $row
}
set res [image create photo -height $h -width $w]
$res copy $image
for {set i 1} {$i<$h-3} {incr i} {
for {set j 1} {$j<$w-3} {incr j} {
set pixels {}
foreach k {-1 0 1} {
set ik [expr {$i+$k}]
foreach l {-1 0 1} {
lappend pixels [lindex $data $ik [expr {$j+$l}]]
}
}
set pix [lindex [lsort -integer $pixels] 4]
if {$pix != [lindex $data $i $j]} {
$res put [format \#%02x%02x%02x $pix $pix $pix] -to $j $i
}
}
}
set res
}Note also Median Filtering in Constant Time
based on tracking partial histograms, and similar code on RosettaCode.See Arts and crafts of Tcl-Tk programming
