Show class colour and filter points by class in segmentation model

[chingyulin]

This PR introduces a section to show the segmentation color and check boxes to adjust points visibility and assignablility.

The color is useful to remind the annotator of the existing labelled points.
The filter is useful to hide labelled points to reduce cognitive load.

UI:

Demo:

1. Raw color filtering:
   

2. Mix color filtering:
   

3. Assign labels only to visible points
   

[ch-sa]

Hi @chingyulin,

thanks for the effort. I think though that making a whole table out of the label list adds a bit too much clutter to the UI.

However, I like the idea with hiding the labeled points.

What about ...

1. adding only a very subtle hide icon on the right side besides the label text (see icon)
   
2. only coloring the bounding box icon in the color of the class (here blue)

[chingyulin]

Hi @ch-sa,

Thank you for the comments.

• I like the eye icon for controlling the visibility, will use it.

• The reason why it is needed to have a new table for segmentation and not to use bounding box table for it is because there can be multiple bounding boxes having the same class. If we use the box table for controlling the visibility of classes, multiple boxes could control the same class, which could cause confusion. I agree that adding a table will clutter the UI under segmentation mode but I don't know a good way to avoid it without changing the bounding box table functionality. In terms of the segmentation workflow, it is not necessary that the bounding box table can have boxes with the same class as is because one would normally just create a box, assign the points in the box with the class, destroy the box; and move on to creating a new box. That is at any given point, there is at most one box in the canvas. However, it would require to repurpose the bounding box table and maybe even rethink about the UI workflow for segmentation. What do you think?