And here comes another great tool made by Jed Smith. This one is similar to CurveTool and allows you to track the color of an area of the image, then applies all that information to a Grade node. It is a lot more efficient and intuitive than the native Nuke tool, and it also comes with instructions so it is really easy to follow.
If you want you can see the code (and many other amazing ones from Jed) on his GitHub.
Expand ColorTracker
Group {
name ColorTracker1
onCreate "\nif nuke.thisNode()\['f_created'].getValue()==True:\n nuke.thisNode()\['f_created'].setValue(False)\n nuke.thisNode().showControlPanel()"
selected true
xpos 399
ypos -58
addUserKnob {20 ColorTracker}
addUserKnob {26 instructions_text l <b>Instructions: T "1). Stabilize your plate around the area you want to track\n2). Crop your plate to just the area you want to analyze\n4). Press Track Color to analyze the footage\n5). Create a matchmove or stabilize grade, and specify your reference frame\n6). You can scale the curve around a specified pivot value on the grade node \n using the color_pivot and color_mult knobs in the ColorTrack tab"}
addUserKnob {26 ""}
addUserKnob {26 label_trackcolor l "<b>Track Color" T " "}
addUserKnob {41 track_color l "Track Color" t "This button will track the color change over the specified framerange and put the data into the intensitydata knob." T CurveTool.go}
addUserKnob {41 intensitydata T CurveTool.intensitydata}
addUserKnob {26 ""}
addUserKnob {26 label_apply_color_track l "<b>Apply Track" T " "}
addUserKnob {3 reference_frame l "reference frame" t "On the specified frame, the calculated color change will have no effect."}
reference_frame 1006
addUserKnob {4 mode l Mode t "If using this node to apply the color transform, choose whether to matchmove or stabilize the sampled color." M {Matchmove Stabilize "" "" "" ""}}
addUserKnob {6 enable_expression_links t "If this is enabled, the grade node will be expression linked to the color track node. Otherwise the keyframes will be baked." -STARTLINE}
enable_expression_links true
addUserKnob {22 create_linked_grade l "Create Linked Grade" t "Creates a grade expression linked to this node. Useful if you need to link the same color transform to many places in your script. " T "## Create Linked Grade\n\nn = nuke.thisNode()\n\nnuke.root().begin()\n\ngrade_node = nuke.createNode('Grade')\ngrade_node.setName('\{0\}_APPLY'.format(n.fullName()))\ngrade_node.addKnob(nuke.Tab_Knob('ColorTrack'))\ngrade_node.addKnob(nuke.Int_Knob('reference_frame', 'reference frame'))\ngrade_node\['reference_frame'].setValue(int(n\['reference_frame'].value()))\ngrade_node.addKnob(nuke.Boolean_Knob('stabilize', 'stabilize'))\ngrade_node\['stabilize'].clearFlag(nuke.STARTLINE)\ngrade_node\['stabilize'].setValue(n\['mode'].getValue())\n\ngrade_node.addKnob(nuke.AColor_Knob('intensitydata', 'intensitydata'))\ngrade_node.addKnob(nuke.AColor_Knob('color_pivot', 'color_pivot'))\ngrade_node.addKnob(nuke.AColor_Knob('color_mult', 'color_mult'))\ngrade_node\['color_pivot'].setValue(\[1,1,1,1])\ngrade_node\['color_mult'].setValue(\[1,1,1,1])\n\n# Set intensity data: expression link if enable_expression_links is set, otherwise copy the animation curve\nintensity_data_knob = grade_node\['intensitydata']\nintensity_data_knob_src = n\['intensitydata']\nif n\['enable_expression_links'].getValue():\n\tintensity_data_knob.setExpression('parent.\{0\}.intensitydata'.format(n.fullName()))\nelse:\n\t# Copy the animation curves from the Color Track node\n\tintensity_data_knob.setAnimated()\n\tfor i, k in enumerate(intensity_data_knob.animations()):\n\t\tif intensity_data_knob_src.isAnimated():\n\t\t\tk.addKey(intensity_data_knob_src.animation(i).keys())\n\n\n\nexprstring = 'stabilize ? 1/(((intensitydata / intensitydata(reference_frame))-color_pivot)*color_mult+color_pivot) : ((intensitydata / intensitydata(reference_frame))-color_pivot)*color_mult+color_pivot'\ngrade_node\['white'].setValue(1, 1) # Split the color knob\nfor i in xrange(4):\n grade_node\['white'].setExpression(exprstring, i)" +STARTLINE}
addUserKnob {6 f_created l "First Created?" +INVISIBLE +STARTLINE}
f_created true
}
Input {
inputs 0
name Input
xpos 400
ypos -729
}
CurveTool {
ROI {0 0 {width} {height}}
autocropdata {160 120 480 360}
intensitydata {0 0 0 0}
maxlumapixdata {140 385}
minlumapixdata {186 -390}
name CurveTool
selected true
xpos 400
ypos -490
}
Output {
name Output1
xpos 400
ypos -226
}
end_group