JDAT-1399: Display Contour Levels in image viewer

[pllim]

Overlay contours on image in viewer. Use cases:

• Overlay contours from same image
• Overlay contours from another image -- Blocked by Freeze contour shapes and overlay on a different image without recalculation glue-viz/glue-jupyter#231
• Read in contours from a file or notebook -- I thought PO says we don't need this? Please clarify! JDAT-1399: Display Contour Levels in image viewer #530 (comment)
• Manually adjust contour levels

Workflow example: #530 (comment)

https://jira.stsci.edu/browse/JDAT-1399

• Also blocked by JDAT-1491: Add API to return a list of human-readable viewer name #643 -- Without this, we cannot apply the contour to tiled viewers.

[astrofrog]

In principle contours are already possible because they were implemented for cubeviz:

I think this meets requirements 1, 2, and 4 in the list above. I'm not sure what 3 really means compared to say 2. Are there any standard formats for storing contours that we might want to support? Isn't 2 enough?

I think it would be nice to be able to customize the contours a bit to be able to turn the labels on/off and change the colors. I've opened an issue here: glue-viz/glue-jupyter#219

[pllim]

Again, perhaps @PatrickOgle can advise.

[PatrickOgle]

The additional desired functionality is to save/load a file containing contour levels or export/load list of contour levels
to/from a notebook like this:

1. Load and display image 1
2. Load and display image 2
3. Match WCS of image 2 to image 1
4. Plot contours on image 2
5. Manually adjust contour levels on image 2
6. Overplot contours from image 2 on image 1 (using existing mechanism)
7. Save contour levels as a list in a notebook (or to a CSV file):
   [1, 20, 40, 55, 100.]
8. Load contour levels back into viewer/layer as a list (or from a CSV file).

The point is that we don't want to type in potentially long lists of numbers in the custom contours tool.
We also want to capture the list for use elsewhere and on other images.

[astrofrog]

That makes sense, thanks!

[PatrickOgle]

@astrofrog Is there a plan/way to export the contour levels to the notebook?

[pllim]

@PatrickOgle , from what I understood from what you said on 2021-05-25, you do not need to save or load contour from file. You only want to transfer contour in memory (in a given active session) from one image to another; this contour in memory will be lost when the session ends, is that correct?

[pllim]

Brute force obviously doesn't work... 😬

viewer.state.layers[0].contour_lim_helper = viewer.state.layers[1].contour_lim_helper
viewer.state.layers[0].contour_visible = True