Finding grain orientation in the weilding heat-affected zone

# gmic macro.gmic HAZ.png --haz_orientation 40 -compose_rgba[0,1]
# $1 : sample size
# $2 : orientation accuracy in degrees (must be a factor of 360)
haz_orientation: -skip ${1=40},${2=10}
  -e[^-1] "sample size : $1 and accuracy : $2.\n"
  -v -
#  -blur 1
  -to_gray -gradient_norm
  ww=@{-1,round(w/$1)}
  hh=@{-1,round(h/$1)}
  -split_tiles $ww,$hh
  -repeat @#
  -local[-1]
    --hough {360/$2},1
    -split[-1] x,2 -+[-2,-1]    #so that 45°==225°
    orientation=@{-1,(xM+0.5)/360*(2*pi)*$2}    #from degree to radian
-v +    confidence=@{-1,iM/ia/w/h} -v -
    dx={cos($orientation+pi/2)*($1*$confidence)}
    dy={sin($orientation+pi/2)*($1*$confidence)}
    -rm[-1]                     #remove hough transform
    -resize 100%,100%,1,4       #4 channels
    -fill 0                     #image initialisation
    -line {$1/2+$dx},{$1/2+$dy},{$1/2-$dx},{$1/2-$dy},1,255,0,0,255
    -line 0,0,0,100%,1,0,255,0,50
    -line 0,0,100%,0,1,0,255,0,50   #green frame
    --resize 100%,100%,1,1 -fill[-1] $orientation
    --fill[-1] $confidence
  -endlocal
    p={round(100*$>/@#)}
#    -progress $p -v + -e[] "\r  "$p% -v -
  -mv[-3--1] 0
  -done
  -append_tiles[0--3:3] $ww,$hh
  -append_tiles[1--2:2] $ww,$hh
  -append_tiles[2--1] $ww,$hh
  -v +