SKIP: gray vs grey

[sciunto]

Description

Recently, I saw a student stuck after typing

io.imread('image.jpg', as_gray=True)

Silently, it loads as a RGB image.

Indeed, the API is as_grey. The problem is that our API is not homogeneous. It seems that US spelling is in majority in our library. I would suggest to either:

• make sure that both gray and grey are working
• raise a warning

Any suggestion @scikit-image/core ?

[jni]

What does RFC mean for those of us that are uninitiated? =)

My preference is for both to work. (I think this is what we do with rgb2grey/rgb2gray?)

[soupault]

Is seems that skimage.io is the only place where as_gray keyword is used.
It won't be a bad idea to support both as_gray and as_grey there. 👍

[sciunto]

Request For Comments, but I have no idea what SKIEP means :D

[soupault]

@sciunto It is our new brand for labelling strategic discussions: SciKit-Image Enhancement Proposal (copy from PEP) 😄 .

[sciunto]

needs a little TM them :)

[sciunto]

Is it trivial to support as_gray along with as_grey? The **kwarg is used for the plugins... it doesn't seem nice to me to go that way. I would prefer to follow a deprecation cycle. Do you agree?

[sciunto]

I notice that in mrphology, we have grey.py and greyreconstruct.py. Ndimage uses grey as well...

[soupault]

matplotlib and Pillow use gray, grayscale.

@sciunto Sorry, I didn't catch your second proposal.

[sciunto]

What I meant is:

• solution 1: we use **kwargs to catch as_gray if as_grey is not set, but **kwargs is used for plugins, so it's not very clean.
• solution 2: we add a new option as_gray with as_grey=None. If as_grey is not None, raise a warning for deprecation.

I prefer solution 2. However, if we go this way (ie in favour of gray), we have to change a lot of stuffs.

[alexdesiqueira]

I'd go with as_gray, since this is the "most used" nomenclature in books, papers, et al. It could confuse some users (I was one of them). For me, @sciunto's solution 2 is the way to go.

[soupault]

@sciunto is there anything else you would like to change?

[sciunto]

I just opened a small PR #3098 but ideally, it would be good to replace other places but deprecations are needed... :(

[PinkFloyded]

As a new user of skimage it seems very strange to keep two versions of the API whenever there is a gray. This pollutes the API surface and for no good reason. I think it makes sense to choose one, deprecate the other and remove it in a major version release.

[jni]

@PinkFloyded I actually agree with you and disagree with past me. 😂 🤷‍♂️ The intention going forward is to follow US convention everywhere. However, this will take time as it requires breaking changes and deprecations. (Not least in graycoprops, which looks weird to me spelled that way. Anyone else?)