for tcl547

grid [canvas .c -w 256 -he 256]
.c create rect 0 0 200 200

set p [image create photo -width 256 -height 256]

set h [expr 255**3]

for {set x 0} {$x<256} {incr x} {
    for {set y 0} {$y<256} {incr y} {

        set a [expr {$x*4/255.0-2}]
        set b [expr {$y*4/255.0-2}]

        set c $a
        set d $b

        set n 0

        while {$n<200} {
                set a [expr {$a*$a-$b*$b+$c}]
                set b [expr {2*$a*$b+$d}]

                if {$a*$a+$b*$b>4} {break}

                incr n
        }

        #.c create rect $x $y $x $y -fill [format #%06x [expr $n*$h/100]]
        #puts "$x $y $a $b $n [format #%06x [expr $n*$h/100]]"
        $p put [format #%06x [expr {$n*$h/200}]] -to $x $y
    }
}

.c create image 128 128 -image $p