Add label specific content

[wosiu]

This is a refactor of: https://github.com/wkentaro/labelme/pull/917

TLDR: Ability to add some generic extra info for label. For example: information about text in a polygon or some other text metadata unique per object.

Testing performed: [x] flake8 . [x] black --line-length 79 --check labelme/ [x] MPLBACKEND='agg' pytest -vsx tests/ [x] manual testing - details below.

[wosiu]

Manual testing:

1. opening existing annotations: and editing:

works fine:

{
  "version": "5.0.1",
  "flags": {},
  "shapes": [
    {
      "label": "class_id",
      "points": [
        [
          193.5494505494505,
          100.3956043956044
        ],
        [
          773.7692307692307,
          68.52747252747253
        ],
        [
          806.7362637362637,
          990.5054945054944
        ],
        [
          223.2197802197802,
          1001.4945054945055
        ]
      ],
      "group_id": 0,
      "content": "\"Sadsa\" 123123\n'dsdsa'  \nescaping \\\" \\\\\"",
      "shape_type": "polygon",
      "flags": {}
    }
  ],
  "imagePath": "2022-05-05 at 12.03.12 copy.png",
  "imageData": null,
  "imageHeight": 1181,
  "imageWidth": 883
}

2. adding new polygon - works as expected.

3. reopeninng edition of exising polygon with previously added concente - works as expected.

[wosiu]

@xulihang, any chances for having this merged and released? 🥺

[xulihang]

I'm afraid that you've mentioned the wrong person. I am the person who created the original pr.

[wosiu]

Oh sorry 🤦 Bumping the question, @wkentaro - any chances for having this merged and released? I'm afraid it'll get drifted again compared to the main branch with time.

[wosiu]

@wkentaro do you need any help, so that it could be merged?

[wkentaro]

@wosiu Can you explain what would be the example use case of this?

[wosiu]

Annotating fragments of image with text for end to end OCR training

[wosiu]

@wkentaro Does it make sense? I can elaborate more if needed or help :) I'm just worried it'll get drifted if we don't merge it.

[wkentaro]

@wosiu Thank you for the reminder and yes the OCR example made the use case clear for me. I'll work on this as the next work.