Provide a widget for drawing regions-of-interest (ROIs) in napari

[niksirbi]

After we've figured out how to represent ROIs in movement—see issue #377, and we've released a minimal version of our napari plugin—see issue #31, we should add a napari widget for defining ROIs.

We'd probably end up working with the napari Shapes layer and the widget would handle the conversions between that format and whatever ROI representation we choose in movement.

[niksirbi]

Copying some relevant comments from #489:

What we actually need is:

• A way for users to assign a name to each created ROI, which napari doesn’t support out of the box.
• Functionality to convert shapes drawn in napari into movement ROI objects (e.g. PolygonOfInterest or LineOfInterest).
• A way to save these ROIs — along with their names — to file, so they can be reused or shared across sessions.

[harsh-bhanushali-05]

Hey, Thank you for feedback. I’ve implemented the second point in draft PR #544 and wanted to check if I’m heading in the right direction. Essentially, the implementation converts the shapes drawn into ROI objects and displays them in a new layer as well.

The convert_shapes_to_roi function takes all the shapes from a specific layer, converts each one into an ROI object, and makes an array of all the shapes in that layer.

Please let me know if I am heading in the right direction