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plotting - Extracting unknown ColorFunction from Plot, Plot3D etc


I wonder if there is a way to extract existing ColorFunction and "override" it with a new function that will depend on original one. This question discusses different ways how to add transparency to 3D plot, including an "extraction procedure" proposed by @RunnyKine:


Trace[Plot[Sin[x], {x, 0, 2 Pi}], _Blend & ] // 
  Flatten // ReleaseHold
Trace[Plot[Sin[x], {x, 0, 2 Pi}, 

    ColorFunction -> "Rainbow"], _Blend &] // Flatten // ReleaseHold
Trace[Plot[Sin[x], {x, 0, 2 Pi}, 
    ColorFunction -> (#^2 &)], _Blend &] // Flatten // ReleaseHold

It works if you know in advance that the ColorFunction uses Blend, but for general ColorFunction (case three in the above code) it doesn't work. These were just examples to illustrate the extraction algorithm. I want a procedure that will work for any plotting object without any assumptions about its ColorFunction.


Is there a way to obtain ColorFunction from plotting functions? I wonder if I'm missing some simple solution a la


ColorFunction /. Options[Plot] (* Automatic .. not very useful *)


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