A simple checkerboard generator for Nuke that doesn't require a specific format. Instead it takes the input format and overwrites the rgba channels with the checkerboard colors.

CS_CheckerBoard.tcl

set cut_paste_input [stack 0]
version 10.5 v7
push $cut_paste_input
Group {
 name CS_CheckerBoard1
 addUserKnob {20 CS_CheckerBoard}
 addUserKnob {41 checker_size T Expression1.checker_size}
 addUserKnob {41 centered T Expression1.centered}
 addUserKnob {41 center l "" -STARTLINE T Expression1.center}
 addUserKnob {41 colorA T Expression1.colorA}
 addUserKnob {41 colorB T Expression1.colorB}
}
 Input {
  inputs 0
  name Input
  xpos -40
  ypos -154
 }
 Expression {
  expr0 "((centered ? x - center.x % (checker_size.w * 2) + checker_size.w * 2 : x) % (checker_size.w * 2) < checker_size.w) == ((centered ? y - center.y % (checker_size.h * 2) + checker_size.h * 2 : y) % (checker_size.h * 2) < checker_size.h) ? colorA.r : colorB.r"
  expr1 "((centered ? x - center.x % (checker_size.w * 2) + checker_size.w * 2 : x) % (checker_size.w * 2) < checker_size.w) == ((centered ? y - center.y % (checker_size.h * 2) + checker_size.h * 2 : y) % (checker_size.h * 2) < checker_size.h) ? colorA.g : colorB.g"
  expr2 "((centered ? x - center.x % (checker_size.w * 2) + checker_size.w * 2 : x) % (checker_size.w * 2) < checker_size.w) == ((centered ? y - center.y % (checker_size.h * 2) + checker_size.h * 2 : y) % (checker_size.h * 2) < checker_size.h) ? colorA.b : colorB.b"
  expr3 "((centered ? x - center.x % (checker_size.w * 2) + checker_size.w * 2 : x) % (checker_size.w * 2) < checker_size.w) == ((centered ? y - center.y % (checker_size.h * 2) + checker_size.h * 2 : y) % (checker_size.h * 2) < checker_size.h) ? colorA.a : colorB.a"
  name Expression1
  selected true
  xpos -40
  ypos -82
  addUserKnob {20 User}
  addUserKnob {14 checker_size R 0 100}
  checker_size 64
  addUserKnob {6 centered +STARTLINE}
  centered true
  addUserKnob {12 center l "" -STARTLINE}
  center {{"width / 2"} {"height / 2"}}
  addUserKnob {19 colorA}
  colorA {0.1 0.1 0.1 1}
  addUserKnob {6 colorA_panelDropped l "panel dropped state" -STARTLINE +HIDDEN}
  addUserKnob {19 colorB}
  colorB {0.2 0.2 0.2 1}
  addUserKnob {6 colorB_panelDropped l "panel dropped state" -STARTLINE +HIDDEN}
 }
 Output {
  name Output
  xpos -40
  ypos -10
 }
end_group