Local averaging with custom neighbourhood

patches-own [ c ]

to setup
  clear-all
  ask patches [
    set c 0
    set pcolor white
  ]
    reset-ticks
end 

to go
  my-diffuse
  colour-patches
  tick
end 

to my-diffuse
  ask patches [
    let level 0
    let n 0
    if x-1y-1 = 1 [
      set n n + 1
      set level level + [c] of patch-at -1 -1]

    if x-1y = 1 [
      set n n + 1
      set level level + [c] of patch-at -1 0]

    if x-1y+1 = 1 [
      set n n + 1
      set level level + [c] of patch-at -1 1]

    if xy-1 = 1 [
      set n n + 1
      set level level + [c] of patch-at 0 -1]

    if xy+1 = 1 [
      set n n + 1
      set level level + [c] of patch-at 0 1]

    if x+1y-1 = 1 [
      set n n + 1
      set level level + [c] of patch-at 1 -1]

    if x+1y = 1 [
      set n n + 1
      set level level + [c] of patch-at 1 0]

    if x+1y+1 = 1 [
      set n n + 1
      set level level + [c] of patch-at 1 1]

    if x-2y-2 = 1 [
      set n n + 1
      set level level + [c] of patch-at -2 -2]

    if x+2y+2 = 1 [
      set n n + 1
      set level level + [c] of patch-at 2 2]


    set c (1 - weight-w) * c + weight-w * level / n + noise-level * one-of [-1 1]
  ]
end 

to colour-patches
  ask patches with [pcolor != black][
    ifelse c > threshold [set pcolor black][ set pcolor scale-color red c threshold 0]]
end