I'll mark as "Good first issue" because I think the example of LogNorm is relatively easy to follow and emulate down the stack. There is a bit of work to argue for the correct Locator and Formatter of the scale, but there must be examples out there.

Hi !
Can I try to work on this ?

See the discussion at #10234, #7294 (comment), #12665 regarding PowerNorm's semantics, though.

Hi @jklymak,

Could you tell me more about where should I start, which files are involved in here ?
I am willing to help for this issue.

colors.py and look at how LogNorm is constructed...

Hi @jklymak could you explain me what this line does please ?

@_make_norm_from_scale(functools.partial(scale.LogScale, nonpositive="mask"))

It makes the norm! Note nonpositive is a kwarg for LogScale. The functools.partial passes nonpsoitive="mask" to the init of the LogScale.

I actually don't know why @anntzer used functors.partial here rather than passing the init kwarg.

I don't really remember, bu I guess that may be because using the init kwarg would have made nonpositive a kwarg to LogNorm, which it wasn't before?

Ok I understand, thank you.
Thus we have to add the 'PowerScale' in 'scale.py' I believe ?

How should we define it ? @jklymak, you said that there must be an example out here.

Again, trace what happens with LogScale...

Hi @jklymak, I started the implementation in the scale.py file of :

• PowerTransform : --> How we should define the distinctions for the base ? It seems that all bases could be fine with this Transform.
• InvertedPowerTransform --> 100% done, it was similar to the InvertedLogTransform in the code architecture.
• PowerScale : --> Do we have to redefine this inhirited method ? set_default_locators_and_formatters(self, axis)

If I add this line :

@_make_norm_from_scale(
    scale.PowerScale,
    init=lambda gamma, vmin=None, vmax=None, clip=False: None)

just before the PowerNorm() class in the colors.py, it means I should access the kwargs for the PowerScale() in the scale.py file, am I right ?
Because I am trying to use them but in visual studio it says for example for vmin that "vmin" is not defined.