Remove empty masks

[klakhov]

Motivation and context

This PR improves CVAT behavior in case of appearing empty masks.

1. In case if some masks become empty as a result of remove underlying pixels feature, empty masks are now deleted and special notification is shown:
   
2. Added support for undo/redo for remove underlying pixels
3. When user starts creating new mask (or editing existing one which was fully erased) eraser and poly-minus tools are blocked
   
4. If user fully erases mask and tries to apply such changes the action is cancelled. (If user wants to delete mask completely he should use Del/Remove actions)
5. Added empty mask validation checks in cvat-core

Fixed bug with copying masks which lead to changing label.

Resolved #7160

How has this been tested?

Checklist

• I submit my changes into the develop branch
• I have created a changelog fragment
• I have updated the documentation accordingly
• I have added tests to cover my changes
• I have linked related issues (see GitHub docs)
• I have increased versions of npm packages if it is necessary
  (cvat-canvas,
  cvat-core,
  cvat-data and
  cvat-ui)

License

• I submit my code changes under the same MIT License that covers the project.
  Feel free to contact the maintainers if that's a concern.

[codecov]

Codecov Report

Merging #7295 (7ccc1f5) into develop (f688908) will decrease coverage by 0.07%.
The diff coverage is 50.96%.

Additional details and impacted files

@@             Coverage Diff             @@
##           develop    #7295      +/-   ##
===========================================
- Coverage    83.24%   83.18%   -0.07%     
===========================================
  Files          373      373              
  Lines        39615    39693      +78     
  Branches      3701     3713      +12     
===========================================
+ Hits         32977    33018      +41     
- Misses        6638     6675      +37     

Components	Coverage Δ
cvat-ui	78.90% <50.96%> (-0.11%)	⬇️
cvat-server	87.12% <ø> (ø)

[bsekachev]

Found inconsistencies:

Still can create empty mask in cvat-canvas module. It can be passed to cvat-core where exception is thrown and message is shown.
In case with other shapes, it is not created, message does not appear

Create a normal mask, modify it to empty => exception is thrown, message is shown
In case of other shapes, it cancels changes, message does not appear

Found problems:
Message: "As a result of removing the underlying pixels, some masks became empty and were subsequently deleted." disappears to fast. I was not even able to read it until the end for the first time.
Message: "As a result of removing the underlying pixels, some masks became empty and were subsequently deleted." appears everytime when I create a mask with enabled "removeUnderlyingPixels"

Let's try to modify the message, splitting it to title and description. Something like this?

[klakhov]

I belive everything is consistent.

Found inconsistencies:

Still can create empty mask in cvat-canvas module. It can be passed to cvat-core where exception is thrown and message is shown. In case with other shapes, it is not created, message does not appear
Why there is no exception with other shapes?

We have the same logic for all shapes in checkNumOfPoints function. If I try to create rect with <4 points then an errror occurs

            const state = new cvat.classes.ObjectState({
                shapeType: ShapeType.RECTANGLE,
                objectType: ObjectType.SHAPE,
                points: [0],
                occluded: false,
                attributes: {},
                frame: 1,
                label: jobInstance.labels[0],
            });
            const [clientID] = await jobInstance.annotations.put([state]);

Create a normal mask, modify it to empty => exception is thrown, message is shown In case of other shapes, it cancels changes, message does not appear

If I try to set rectangle to <4 points and save it then the same exeption is thrown. Is there even a way to create such case for other shapes than masks?

Found problems: Message: "As a result of removing the underlying pixels, some masks became empty and were subsequently deleted." disappears to fast. I was not even able to read it until the end for the first time. Message: "As a result of removing the underlying pixels, some masks became empty and were subsequently deleted." appears everytime when I create a mask with enabled "removeUnderlyingPixels"

Let's try to modify the message, splitting it to title and description. Something like this?

Fixed the message.

[bsekachev]

How can you create/edit a rectangle setting it less then 4 points?

[bsekachev]

We have the same logic for all shapes in checkNumOfPoints function. If I try to create rect with <4 points then an errror occurs

Yes, we have such check in cvat-core

But cvat-canvas, cvat-ui will not even try to save a rectangle with less number of points for a rectangle.
The same for polyshapes. For example when polygon has only three points, the interface doesn't allow to remove any more points:

The idea is to prevent useless exception when user does something wrong.
With masks we can see these exceptions in regular work now, with other shapes, we can't

[bsekachev]

I believe locking polygon-minus and eraser tool if mask is empty in cvat-canvas would be a good solution in first.
This way let users avoid misclicking a button. Probably it is one of ways why such masks are created, not intentionally
One more way, is when we finished drawing a mask using eraser/polygon minus, creating a new shape will have this tool as default one. What is also not really user friendly.

Finally if a user created an empty mask in cvat-canvas, it should not raise shape.drawn event

[klakhov]

How can you create/edit a rectangle setting it less then 4 points?

Using cvat-core api via code.

I believe locking polygon-minus and eraser tool if mask is empty in cvat-canvas would be a good solution in first.
Finally if a user created an empty mask in cvat-canvas, it should not raise shape.drawn event

Okay, ill think about that

[bsekachev]

There is an issue with inserting. Class has changed

[bsekachev]

There will be a problem with huge memory consumption

In closure it refers to variable masks that contains all unpacked masks stored on the frame (imagine that there are 100+ masks per frame).
And undo/redo stores up to 128 actions as far as I remember

It gigabytes of data

[klakhov]

masks store not all masks on the frame but only affected ones, but still there can be a problem.
Ive added limitations to annotation history, so there only can be 20 undos for removing underlying pixels. (maybe we should change this number to even lower value)

[klakhov]

@bsekachev

The issue with copying mask that was changing class seems to be reproducible on develop, its separate bug but Ive fixed it.

I cant really reproduce the issue with color changing on last verion of PR, so maybe its fixed already.