Imviz astrowidgets API: save

[pllim]

Description

This pull request is to implement the save method as per astrowidgets API definition.

Fixes #719

xref #632

Would be nice to have some inputs from @maartenbreddels though I think this PR is still acceptable without:

• Can we resolve How to ask save_png not to pop up a file dialog when filename is given? bqplot/bqplot#1393 ? If not, we need to consider these two popup behaviors:
  • The popup makes browser warns me of "multiple downloads" (Wombat alert!).
  • The popup pops up twice for a single save attempt; not sure why.

Screenshots

What you actually see on browser:

What it saves out:

I did blink to another image, and it does save out the one that is displayed.

Checklist for package maintainer(s)

This checklist is meant to remind the package maintainer(s) who will review this pull request of some common things to look for. This list is not exhaustive.

• Are two approvals required? Branch protection rule does not check for the second approval. If a second approval is not necessary, please apply the trivial label.
• Do the proposed changes actually accomplish desired goals? Also manually run the affected example notebooks, if necessary.
• Do the proposed changes follow the STScI Style Guides?
• Are tests added/updated as required? If so, do they follow the STScI Style Guides?
• Are docs added/updated as required? If so, do they follow the STScI Style Guides?
• Did the CI pass? If not, are the failures related?
• Is a change log needed? If yes, is it added to CHANGES.rst?
• Is a milestone set? Milestone is only currently required for PRs related to Imviz MVP.
• After merge, any internal documentations need updating (e.g., JIRA, Innerspace)?

[codecov]

Codecov Report

Merging #759 (a2d80b5) into main (cf3a026) will decrease coverage by 0.18%.
The diff coverage is 20.00%.

@@            Coverage Diff             @@
##             main     #759      +/-   ##
==========================================
- Coverage   63.27%   63.08%   -0.19%     
==========================================
  Files          65       65              
  Lines        4324     4329       +5     
==========================================
- Hits         2736     2731       -5     
- Misses       1588     1598      +10     

Impacted Files	Coverage Δ
jdaviz/configs/imviz/helper.py	97.05% <20.00%> (-1.66%)	⬇️
...configs/default/plugins/data_tools/file_chooser.py	65.71% <0.00%> (-3.43%)	⬇️

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[ojustino]

If I'm able to review, I can give this a pass. I tried using both the save button in the toolbar and the programmatic method with imviz.save().

I have a few comments.

• I did not get the "multiple downloads" alert on Firefox but did get it on Edge. I agree that this would be a nice thing to fix.
• I agree that it would be good to not trigger a file dialog after the user runs imviz.save().
• My images had the same gray border at their top and right edges as @pllim's. Are these intentional?

[pllim]

Re: Gray border -- Maybe @mariobuikhuizen can comment?

[ojustino]

Am I OK to add myself as a reviewer? Depending on how important it is to solve the gray border question, I can give approval since it seems like the other problems come from elsewhere.

[pllim]

@ojustino , feel free! And looks like we forgot to update the codeowners file when you joined. Will fix! See #789.

[rosteen]

@ojustino My two cents is that you should always feel free to add yourself as a reviewer.

[ojustino]

The save process went smoothly for me. I'm curious about how to eliminate the gray borders and it would be nice to see the test in action, but I don't think either should prevent a merge.

[pllim]

how to eliminate the gray borders

I think that is a question for @maartenbreddels or @mariobuikhuizen . This API simply exposes this functionality from bqplot:

https://github.com/bqplot/bqplot/blob/b18af05244d3f4c592e09be46a4334584ab2600f/bqplot/figure.py#L164

Could be the VueJS stuff needs fixing, or maybe bqplot; I don't know.

[rosteen]

FYI it looks like the gray border doesn't occur on my setup - even if zoomed out to where there are areas of no data around the edges, the saved image has the same color as the viewer does in those areas. So my thought that the gray happens where there is no data seems to be incorrect. My environment (on Mac OSX, firefox):

astropy                           4.2.1
bqplot                            0.12.30                       /Users/rosteen/opt/anaconda3/envs/viz_dev/lib/python3.9/site-packages
bqplot-image-gl                   1.4.3
glue                              0.13
glue-astronomy                    0.2
glue-core                         1.0.1.dev81+g5978a927         /Users/rosteen/projects/glue
glue-jupyter                      0.7
glue-vispy-viewers                1.0.2
gwcs                              0.16.1
ipydatawidgets                    4.2.0
ipygoldenlayout                   0.4.0
ipyvue                            1.5.0
ipyvuetify                        1.7.0
ipywidgets                        7.6.3
jdaviz                            1.2.dev395+g2384547.d20210810 /Users/rosteen/projects/jdaviz
jupyter-client                    6.1.12
jupyter-contrib-core              0.3.3
jupyter-core                      4.7.1
jupyter-server                    1.8.0
matplotlib                        3.4.2
numpy                             1.20.3
photutils                         1.1.0
Pillow                            8.2.0
specutils                         1.3.dev121+gf0686ed0          /Users/rosteen/projects/specutils
traitlets                         5.0.5
voila                             0.2.10
widgetsnbextension                3.5.1

[rosteen]

Approving, since everything worked for me and it seems the fix to the gray border may be upstream.