A simple edge extend node for Nuke.

CS_EdgeExtend.tcl

set cut_paste_input [stack 0]
version 9.0 v8
push 0
push $cut_paste_input
Group {
 inputs 2
 name CS_EdgeExtend1
 selected true
 xpos -150
 ypos 1214
 addUserKnob {20 CS_EdgeExtend}
 addUserKnob {6 premultiplied_input l "Premultiplied input" +STARTLINE}
 premultiplied_input true
 addUserKnob {20 core_alpha_erode l "Core alpha erode" n 1}
 addUserKnob {41 size T FilterErode1.size}
 addUserKnob {41 filter T FilterErode1.filter}
 addUserKnob {20 endGroup n -1}
 addUserKnob {20 extension l Extension n 1}
 addUserKnob {41 size_2 l size T Blur1.size}
 addUserKnob {41 filter_2 l filter T Blur1.filter}
 addUserKnob {20 endGroup_2 l endGroup n -1}
 addUserKnob {20 clamp_extension l "Clamp extension" n 1}
 addUserKnob {41 minimum T Clamp1.minimum}
 addUserKnob {41 minimum_enable l enable -STARTLINE T Clamp1.minimum_enable}
 addUserKnob {41 maximum T Clamp1.maximum}
 addUserKnob {41 maximum_enable l enable -STARTLINE T Clamp1.maximum_enable}
 addUserKnob {20 endGroup_3 l endGroup n -1}
 addUserKnob {20 final_alpha_erode l "Final alpha erode" n 1}
 addUserKnob {41 size_1 l size T FilterErode2.size}
 addUserKnob {41 filter_1 l filter T FilterErode2.filter}
 addUserKnob {20 endGroup_1 l endGroup n -1}
}
 Input {
  inputs 0
  name Inputmask
  xpos 620
  ypos 350
  number 1
 }
 Dot {
  name Dot10
  xpos 654
  ypos 1098
 }
 Input {
  inputs 0
  name Input
  xpos 290
  ypos 350
 }
 Dot {
  name Dot5
  xpos 324
  ypos 450
 }
set N348fdc00 [stack 0]
 Dot {
  name Dot8
  xpos 104
  ypos 450
 }
 FilterErode {
  size 0
  name FilterErode2
  xpos 70
  ypos 680
 }
 Dot {
  name Dot9
  xpos 104
  ypos 930
 }
push $N348fdc00
 Dot {
  name Dot1
  xpos 434
  ypos 450
 }
set N34932c00 [stack 0]
 Unpremult {
  name Unpremult2
  xpos 400
  ypos 494
 }
push $N348fdc00
 Switch {
  inputs 2
  which {{parent.premultiplied_input}}
  name Switch1
  tile_color 0xff00ff
  xpos 290
  ypos 494
 }
 set C34932400 [stack 0]
 FilterErode {
  size 3
  name FilterErode1
  xpos 290
  ypos 560
 }
 Premult {
  name Premult2
  xpos 290
  ypos 614
 }
set N3494f800 [stack 0]
 Dot {
  name Dot7
  xpos 214
  ypos 618
 }
 Dot {
  name Dot6
  xpos 214
  ypos 858
 }
push $N3494f800
 Blur {
  channels rgba
  size 2
  filter box
  crop false
  name Blur1
  xpos 290
  ypos 686
 }
 Unpremult {
  name Unpremult1
  xpos 290
  ypos 734
 }
 Clamp {
  channels rgba
  minimum_enable false
  maximum_enable false
  name Clamp1
  xpos 290
  ypos 782
 }
 Merge2 {
  inputs 2
  name Merge2
  xpos 290
  ypos 854
 }
 Copy {
  inputs 2
  channels alpha
  name Copy2
  xpos 290
  ypos 913
 }
set N528d5c00 [stack 0]
 Dot {
  name Dot2
  xpos 434
  ypos 930
 }
 Premult {
  name Premult3
  xpos 400
  ypos 998
 }
push $N528d5c00
clone $C34932400 {
  inputs 2
  xpos 290
  ypos 998
  selected false
 }
 Dot {
  name Dot4
  xpos 324
  ypos 1098
 }
set N54b2000 [stack 0]
push $N34932c00
 Dot {
  name Dot3
  xpos 544
  ypos 450
 }
 Keymix {
  inputs 3
  channels rgba
  name Keymix1
  xpos 510
  ypos 1094
 }
 Dot {
  name Dot11
  xpos 544
  ypos 1194
 }
push $N54b2000
 Switch {
  inputs 2
  which {{"\[expr \{\[exists parent.input1]\}]"}}
  name Switch3
  tile_color 0xff00ff
  xpos 290
  ypos 1190
 }
 Output {
  name Output
  xpos 290
  ypos 1286
 }
end_group