[Doc]: Improve "Creating Colormaps" tutorial

[timhoffm]

Documentation Link

https://matplotlib.org/devdocs/tutorials/colors/colormap-manipulation.html

Problem

• Passing a lut parameter should be a side note, not be used everywhere in the tutorial.
• "Getting colormaps and accessing their values" is slightly off. - (Re)move or rephrase tutorial title and/or section title
• Introductory paragraph on "ListedColormap and LinearSegmentedColormap" is wordy and unspecific without conveying much information.
• ...

Suggested improvement

I think we need essentially a complete rewrite / reorg.

Matplotlib Version

3.5.0

[jklymak]

Documentation Link

https://matplotlib.org/devdocs/tutorials/colors/colormap-manipulation.html

Problem

• Passing a lut parameter should be a side note, not be used everywhere in the tutorial.

Perhaps I'm misunderstanding your complaint here? The way you create a colormap in Matlab and most other scientific computing packages that I know of is very simple - you pass an RGB lookup table. Most colormaps available publicly from other software are created and shared via the lookup table. Performing carpentry on a lookup table is the same as performing carpentry on a numpy array, so it is very easy. Finally, all the recent colormaps (viridis, magma, inferno, plasma, twilight, turbo) are listed colormaps, and so far as I know the tools to create perceptually uniform colormaps all create lookup tables. So passing a lookup table, which was previously completely absent from the documentation, was the point of the tutorial, not a sidenote.

Conversely LinearSegmentedColormaps are very elegant, and not digitized, but almost impossible to manipulate, and completely Matplotlib specific. While we have a lot of historic colormaps written this way, it seems to me most users will not create or perform carpentry on colormaps this way.

• "Getting colormaps and accessing their values" is slightly off. - (Re)move or rephrase tutorial title and/or section title
• Introductory paragraph on "ListedColormap and LinearSegmentedColormap" is wordy and unspecific without conveying much information.

Certainly this could be tightened, but the introduction is necessary for folks who don't know what those concepts are...

[timhoffm]

Perhaps I'm misunderstanding your complaint here?

Yes, will clarify later.