Fix saving of flow fields and cell probability in GUI

[qin-yu]

Hi @carsen-stringer, I noticed that _save_flows() was obsolete while trying to save flows in the GUI. I updated the function and tested it on a 3D TIFF and a 2D PNG. I hope this covers all cases.

[codecov]

Codecov Report

All modified and coverable lines are covered by tests ✅

Project coverage is 52.68%. Comparing base (c913196) to head (95e2f60).
Report is 35 commits behind head on main.

Additional details and impacted files

@@            Coverage Diff             @@
##             main    #1103      +/-   ##
==========================================
- Coverage   52.69%   52.68%   -0.02%     
==========================================
  Files          18       18              
  Lines        4302     4328      +26     
==========================================
+ Hits         2267     2280      +13     
- Misses       2035     2048      +13     

☔ View full report in Codecov by Sentry.
📢 Have feedback on the report? Share it here.

[qin-yu]

Just realised there’s no notification when saving starts or finishes. Now:

...
...
2025-02-10 02:37:12,482 [INFO] ~~~ FINDING MASKS ~~~
2025-02-10 02:37:15,230 [INFO] >>>> TOTAL TIME 2.75 sec
2025-02-10 02:37:15,239 [INFO] 111 cells found with model in 2.968 sec
GUI_INFO: 111 masks found
GUI_INFO: creating cellcolors and drawing masks  <---- segmentation finishes here
GUI_INFO: saving flows and cellprob to tiff  <---- after CTRL + F
GUI_INFO: saved flows and cellprob

[carsen-stringer]

thanks so much! made a few small changes and merged it