patch_explorer :

  N=32

  P=17

  -v -
  P2={int($P/2)} P1={$P-$P2-1}
  -nm[-1] img

  # Select initial patch.
  -v + -e[^-1] "Select a patch." -v -
  -w[img] -1,-1,1,0,"Select a patch"
  -do
    -wait[0]
    x=@{!,x}
    y=@{!,y}
    -if {$x>=0}
      --rectangle[img] {$x-$P1},{$y-$P1},{$x+$P2},{$y+$P2},0.5,255,255,0
      -rectangle[-1] {$x-$P1},{$y-$P1},{$x+$P2},{$y+$P2},1,0xFFFFFFFF,0,255,0
      -text_outline[-1] "Coords : ("$x","$y")",2,2,13,2,1,255,255,255
      -w[-1] -rm[-1]
      --crop[img] {$x-$P1},{$y-$P1},{$x+$P2},{$y+$P2}
      -r[-1] 300,300 -grid[-1] {100/$P}%,{100/$P}%,0,0,1,0
      -w1[-1] 300,300,0,0,"Patch view" -rm[-1]
    -endif
  -while {@!" && "!@{!,b}}
  -if @! -v + -e[0--3] "Patch selected at ("$x,$y")." -v -
  -else -v + -e[0--3] "No patch selected. exiting." -return
  -endif

  # Compute SSD with selected patch, and get N best matchs.
  -v + -e[^-1] "Compute similar patchs." -v -
  -i[visu] [img]
  x0=$x y0=$y
  --crop[img] {$x0-$P1},{$y0-$P1},{$x0+$P2},{$y0+$P2} -nm[-1] patch
  --ssd_patch[-2,-1] 0,0 -nm[-1] ssd
  -repeat $N
    xyzc=@{ssd,c} x={arg(1,$xyzc)} y={arg(2,$xyzc)} ssd=@{ssd,($xyzc)}
    -rectangle[ssd] {$x-$P1},{$y-$P2},{$x+$P1},{$y+$P2},1,inf
    -rectangle[visu] {$x-$P1},{$y-$P2},{$x+$P1},{$y+$P2},{1/(1.5+$>)},0,255,0
    -rectangle[visu] {$x-$P1},{$y-$P2},{$x+$P1},{$y+$P2},1,0xFFFFFFFF,0,255,0
    ($ssd,$x,$y)
  -done
  -rm[ssd]
  -a[-$N--1] y -nm[-1] best
  --r[patch] 300,300 -grid[-1] {100/$P}%,{100/$P}%,0,0,1,0 -w1[-1] 300,300,0,0,"Reference patch" -rm[-1]
  -w[] -1,-1,-1,-1,"Best matches"

  # Compute best patch mosaic.
  -repeat $N
    ssd=@{best,(0,$>)}
    x=@{best,(1,$>)}
    y=@{best,(2,$>)}
    --crop[img] {$x-$P1},{$y-$P1},{$x+$P2},{$y+$P2}
    -r[-1] 80,80,1,3,3 -frame[-1] 1,1,0 -frame[-1] 20,20,255
    -text[-1] "\#"$>" SSD="{_sqrt($ssd)},5,2,13,1,0
    -frame[-1] 1,1,0
  -done
  --[-$N--1] 255 -append_tiles[-$N--1] , -+[-1] 255
  -w4[-1] -1,-1,0,0,"Mosaic of best patchs"

  # Explore patchs
  -v + -e[^-1] "Start patch exploration." -v -
  -do
    -wait[0]
    x=@{!,x}
    y=@{!,y}
    -if {$x>=0}
      i=0 d=inf -repeat $N p=@{best,(1,$>)} q=@{best,(2,$>)} nd={sqrt(($x-$p)^2+($y-$q)^2)} -if {$nd<$d} d=$nd i=$> -endif -done
      xn=@{best,(1,$i)} yn=@{best,(2,$i)} ssdn=@{best,(0,$i)}
      [visu] -rectangle[-1] {$xn-$P1},{$yn-$P2},{$xn+$P1},{$yn+$P2},0.5,255,255,0
      -text_outline[-1] "Coords : ("$x","$y")",2,2,13,2,1,255,255,255
      -w[-1] -rm[-1]

      --crop[img] {$xn-$P1},{$yn-$P1},{$xn+$P2},{$yn+$P2}

      --r[-1] 300,300 -grid[-1] {100/$P}%,{100/$P}%,0,0,1,0
      -text_outline[-1] "SSD^1/2 : "{_sqrt($ssdn)}"\nRank \#"{$i+1},2,2,13,2,1,255,255,255
      -w3[-1] 300,300,0,0,"Patch view" -rm[-1]

      --[-1] [patch] -norm[-1] -r[-1] 300,300 -grid[-1] {100/$P}%,{100/$P}%,0,0,1,0
      -w2[-1] 300,300,1,0,"Patch difference" -rm[-1]

    -endif
  -while @!
  -rm
  -v +