support colormodel in px.imshow

[emmanuelle]

I just discovered that go.Image has a colormodel attributes, which makes it possible in particular to support hsl values. It'd be nice to support this in px.imshow as well.

[emmanuelle]

this would mean adding a colormodel attribute in px.imshow, corresponding tests in https://github.com/plotly/plotly.py/blob/master/packages/python/plotly/plotly/tests/test_core/test_px/test_imshow.py, and an example in the documentation (which could be inspired by https://scikit-image.org/docs/dev/auto_examples/color_exposure/plot_rgb_to_hsv.html)

[liudj2008]

@emmanuelle I am interested to work on it.

To be clear,

1. Should the tests be updated? It seems like no tests were written for colormodel.
2. colormodel includes ['rgb', 'rgba', 'rgba256', 'hsl', 'hsla'], should all of these be considered?

Thanks!

[emmanuelle]

Hi @liudj2008 thank you very much :-). My idea was to add a colormodel argument to px.imshow which could be either rgb or hsl; handling transparency can be done automatically depending on the number of channels of the image array, as done in https://github.com/plotly/plotly.py/blob/master/packages/python/plotly/plotly/express/_imshow.py#L433

One test could be added to check that the colormodel argument is used in the specification in the plotly Figure. Indeed, there are no tests yet related to colormodel.

[liudj2008]

Hi @emmanuelle , there are two errors occurred during checks: plotlyjs_dev_build and build-doc. Not sure what happened there. Could you help me take a look? Thanks!

Here is the RP link:
#2833