CompStart

Pro Lessons Courses Elements Software

Median GPU

ToolSets / Filter

Filter

2026-09-07

ToolSets/filter/medianGPU.nk

filter

median

gpu

blink

denoise

cleanup

utility

View on GitHub

GPU 5×5 median filter in Blink, with a threshold that keeps original pixels where they differ from the median.

Median GPU runs a component-wise 5×5 median on the GPU through a Blink kernel (edge-clamped neighborhood). It is a fast spatial filter for reducing salt-and-pepper and similar spike noise without a CPU median node.

A threshold control compares the source to the median result per channel. Where the absolute difference meets or exceeds the threshold, the original pixel is kept; where it stays below, the median value is used. The strongest channel difference drives the mask, so edges and stronger detail are less likely to be smoothed away.

Use it in beauty and cleanup passes when you want median-style noise reduction with a simple gate on how much the filter may change the image. Tune threshold low for stronger smoothing, higher to protect contrast and fine structure.

Script code

set cut_paste_input [stack 0]
version 9.0 v7
push $cut_paste_input
Group {
 name medianGPU
 tile_color 0x421010ff
 selected true
 xpos 123
 ypos 420
 addUserKnob {20 User l medianGPU}
 addUserKnob {7 threshold R 0 0.01}
 threshold 0.00168
 addUserKnob {26 ""}
 addUserKnob {22 btn l DerekVFX.ca T "nuke.tcl('start', 'https://derekvfx.ca')" +STARTLINE}
}
 Input {
  inputs 0
  name Input
  xpos 32
  ypos -442
 }
set N3a92400 [stack 0]
 Dot {
  name Dot1
  xpos -99
  ypos -438
 }
 BlinkScript {
  ProgramGroup 1
  KernelDescription "1 \"Median5x5Kernel\" iterate componentWise 531b6be6f791b8b83e92cc6474e2f2cdcd4974e549f6e5c6a6576b9cc2f40ab7 2 \"imageIn\" Read Ranged2D \"imageOut\" Write Point 0"
  kernelSource "kernel Median5x5Kernel : public ImageComputationKernel<eComponentWise>\n\{\n  Image<eRead, eAccessRanged2D, eEdgeClamped> imageIn; \n  Image<eWrite, eAccessPoint> imageOut;          \n\n  void init()\n  \{\n    imageIn.setRange(-2, -2, 2, 2);\n  \}\n\n  void process(int2 pos)\n  \{\n    float vals\[25];\n\n    for (int j = -2, index = 0; j <= 2; j++) \{\n      for (int i = -2; i <= 2; i++, index++) \{\n        vals\[index] = imageIn(i, j);\n      \}\n    \}\n   \n    //The median function takes an array of floating-point values and an array length.\n    imageOut() = median(vals, 25);\n    \n  \}\n\};"
  rebuild ""
  name median
  xpos -133
  ypos -387
 }
set N3a93000 [stack 0]
 Viewer {
  frame 1043
  frame_range 1000-1092
  name Viewer1
  xpos -338
  ypos -273
 }
push $N3a92400
push $N3a93000
 Dot {
  name Dot2
  xpos -99
  ypos -310
 }
 MergeExpression {
  inputs 2
  temp_name0 red
  temp_expr0 "abs(Ar-Br) >= threshold ? 1 : 0"
  temp_name1 green
  temp_expr1 "abs(Ag-Bg) >= threshold ? 1 : 0"
  temp_name2 blue
  temp_expr2 "abs(Ab-Bb) >= threshold ? 1 : 0"
  temp_name3 mask
  temp_expr3 max(red,green,blue)
  expr0 "mask == 1 ? Ar : Br"
  expr1 "mask == 1 ? Ag : Bg"
  expr2 "mask == 1 ? Ab : Bb"
  expr3 mask
  name MergeExpression1
  xpos 32
  ypos -314
 }
push $N3a93000
 Output {
  name Output1
  xpos 32
  ypos -245
 }
end_group