铸造核武器中的色差

Question

所以我试图用Python代码直接创建一个绘画节点组，这样我就可以在未来的项目中使用它，但我似乎无法从这个色差公式中获得nuke公式的强大部分（我也是Nuke新手，所以如果有更好的方法写这篇文章，请让我知道这会很棒，谢谢，或者如果我完全做错了，也请让我知道）

The following formula for color difference is used to create the difference image: |(r1,g1,b1) – (r2,g2,b2)| = ((r1 – r2)^2 + (g1 –g2)^2 + (b1 – b2)^2)^1/2.

nRedShuffle = nuke.nodes.Shuffle()
nRedShuffle['red'].setValue('red')
nRedShuffle['green'].setValue('red')
nRedShuffle['blue'].setValue('red')
nRedShuffle['alpha'].setValue('red')

nGreenShuffle = nuke.nodes.Shuffle()
nGreenShuffle['red'].setValue('green')
nGreenShuffle['green'].setValue('green')
nGreenShuffle['blue'].setValue('green')
nGreenShuffle['alpha'].setValue('green')

#...(so on for the rest of rgba1 and rgba2)

nGreenShuffle2 = nuke.nodes.Shuffle()
nGreenShuffle2['red'].setValue('green')
nGreenShuffle2['green'].setValue('green')
nGreenShuffle2['blue'].setValue('green')
nGreenShuffle2['alpha'].setValue('green')

nBlueShuffle2 = nuke.nodes.Shuffle()
nBlueShuffle2['red'].setValue('blue')
nBlueShuffle2['green'].setValue('blue')
nBlueShuffle2['blue'].setValue('blue')
nBlueShuffle2['alpha'].setValue('blue')

#I am having troubles with the powers below

redDiff = nuke.nodes.Merge2(operation='minus', inputs=[nRedShuffle2, nRedShuffle])
redDiffMuli = nuke.nodes.Merge2(operation='multiply', inputs=[redDiff, redDiff])

greenDiff = nuke.nodes.Merge2(operation='minus', inputs=[nGreenShuffle2, nGreenShuffle])
greenDiffMuli = nuke.nodes.Merge2(operation='multiply', inputs=[greenDiff, greenDiff])

blueDiff = nuke.nodes.Merge2(operation='minus', inputs=[nBlueShuffle2, nBlueShuffle])
blueDiffMuli = nuke.nodes.Merge2(operation='multiply', inputs=[blueDiff, blueDiff])

redGreenAdd = nuke.nodes.Merge2(operation='plus', inputs=[redDiffMuli, greenDiffMuli]) 
redGreenBlueAdd =  nuke.nodes.Merge2(operation='plus', inputs=[redGreenAdd, blueDiffMuli]) 

Answer 1

这里至少有两种方法可以为两个图像实现Color Difference公式。您可以在合并节点中使用differenceop，也可以在字段中为MergeExpression节点内的每个通道编写公式：

每个通道的表达式如下所示：

abs(Ar-Br)
abs(Ag-Bg)
abs(Ab-Bb)

Python命令

您可以使用.nodes.MergeExpression方法：

import nuke

merge = nuke.nodes.MergeExpression(expr0='abs(Ar-Br)', 
                                   expr1='abs(Ag-Bg)', 
                                   expr2='abs(Ab-Bb)')

或常规.createNode语法：

merge = nuke.createNode('MergeExpression')

merge['expr0'].setValue('abs(Ar-Br)')
merge['expr1'].setValue('abs(Ag-Bg)')
merge['expr2'].setValue('abs(Ab-Bb)')

完整代码版本

import nuke
import nukescripts

red = nuke.createNode("Constant")
red['color'].setValue([1,0,0,1])

merge = nuke.createNode('MergeExpression')
merge['expr0'].setValue('abs(Ar-Br)')
merge['expr1'].setValue('abs(Ag-Bg)')
merge['expr2'].setValue('abs(Ab-Bb)')

yellow = nuke.createNode("Constant")
yellow['color'].setValue([1,1,0,1])

merge.connectInput(0, yellow)
nuke.toNode('MergeExpression1').setSelected(True)

nukescripts.connect_selected_to_viewer(0)

# Auto-alignment in Node Graph
for everyNode in nuke.allNodes():
    everyNode.autoplace()

考虑一下MergeExpression节点比常规Merge(difference)节点慢得多