Label formats

When you label a sample and press the save button, you've created a label for that sample. Labels come in different types, with the available options determined by the type of the corresponding sample.

When downloading or uploading labels using the Python SDK, the format of the attributes field depends on the type of label. The different formats are described here.

A label can additionally also contain Object attributes and Image attributes.

Image

Segmentation labels

Format of the attributes field in client.get_label():

{
  "format_version": "0.1",
  "annotations": [
    {
      "track_id": 1, // the track id. A single object has the same track_id across frames. 0.
      "id": 1, // this is a legacy field and is always equal to track_id.
      "category_id": 1 // this is a category id
    },
    {
      "track_id": 2,
      "id": 2,
      "category_id": 1
    },
    {
      "track_id": 3,
      "id": 3,
      "category_id": 4
    }
  ],
  "segmentation_bitmap": {
    "url": "https://segmentsai-staging.s3.eu-west-2.amazonaws.com/assets/davy/ddf55e99-1a6f-42d2-83e9-8657de3259a1.png"
  }
}

Thesegmentation_bitmap_urlrefers to a 32-bit RGBA png image which contains the segmentation masks. The alpha channel is set to 255, and the remaining 24-bit values in the RGB channels correspond to the object ids in the annotations list. Unlabeled regions should have a value of 0. Because of the large dynamic range, these png images may appear black in an image viewer.

When downloading a label, you can use the utility function utils.load_label_bitmap_from_url(url) in the Python SDK to load the label bitmap as a numpy array containing object ids.

When uploading a label, the easiest way to transform a segmentation bitmap into this format and upload it is by using the util functionbitmap2file:

from segments.utils import bitmap2file

# segmentation_bitmap is a numpy array of type np.uint32, with values corresponding to instance_ids
file = bitmap2file(segmentation_bitmap)
asset = client.upload_asset(file, "label.png")
segmentation_bitmap_url = asset.url

For a full example of uploading model-generated labels to Segments.ai, please refer to this blogpost.

Vector labels (bounding box, polygon, polyline, keypoint)

Format of the attributes field in client.get_label():

{
  "format_version": "0.1",
  "annotations": [
    {
      "track_id": 1, // the track id. A single object has the same track_id across frames.
      "id": 1, // this is a legacy field and is always equal to track_id.
      "category_id": 1, // the category id
      "type": "bbox", // refers to the annotation type (bounding box)
      "points": [
        [12.34, 56.78], // x0, y0 (upper left corner of bbox)
        [90.12, 34.56]  // x1, y1 (lower right corner of bbox)
      ]
    },
    {
      "track_id": 2,
      "id": 2,
      "category_id": 2,
      "type": "polygon", // refers to the annotation type (polygon)
      "points": [
        [12.34, 56.78], // x0, y0 (starting point of the polygon)
        [90.12, 34.56], // x1, y1
        [78.91, 23.45], // x2, y2
        [67.89, 98.76], // x3, y3
        [54.32, 10.01]  // x4, y4
      ]
    },
    {
      "track_id": 3,
      "id": 3,
      "category_id": 3,
      "type": "polyline", // refers to the annotation type (polyline)
      "points": [
        [12.34, 56.78], // x0, y0 (starting point of the polyline)
        [90.12, 34.56], // x1, y1
        [78.91, 23.45], // x2, y2
        [67.89, 98.76], // x3, y3
        [54.32, 10.01]  // x4, y4
      ]
    },
    {
      "id": 4,
      "track_id": 4,
      "category_id": 4,
      "type": "point", // refers to the annotation type (keypoint)
      "points": [
        [12.34, 56.78] // x, y (coordinates of keypoint)
      ]
    },
  ],
  "links": [
    {
      "from_id": 1,
      "to_id": 2,
      "attributes": {} // the link attributes
    }
  ]
}

Image sequence

Segmentation labels

Format of the attributes field in client.get_label():

{
  "format_version": "0.1",
  "frames": [
    { ... },
    { ... },
    { ... }
  ]
}

Name	Type
format_version	string	Format version.
frames	array of segmentation labels	List of segmentation labels (one per frame in the sequence).

Vector labels (bounding box, polygon, polyline, keypoint)

Format of the attributes field in client.get_label():

{
  "format_version": "0.2",
  "frames": [
    { ... },
    { ... },
    { ... }
  ],
  "links": [
    {
      "from_id": 1,
      "to_id": 2,
      "attributes": {} // the link attributes
    }
  ]
}

Where each frames object has the following format:

{
  "format_version": "0.1",
  "timestamp": "00001", // In nanoseconds. This field is only included if the sample has a timestamp
  "annotations": [
    {
      "track_id": 1, // the track id. A single object has the same track_id across frames.
      "id": 1, // this is a legacy field and is always equal to track_id.
      "category_id": 1, // the category id
      "is_keyframe": true, // whether this frame is a keyframe
      "type": "bbox", // refers to the annotation type (bounding box)
      "points": [
        [12.34, 56.78], // x0, y0 (upper left corner of bbox)
        [90.12, 34.56]  // x1, y1 (lower right corner of bbox)
      ]
    },
    {
      "track_id": 2,
      "id": 2,
      "category_id": 2,
      "is_keyframe": true,
      "type": "polygon", // refers to the annotation type (polygon)
      "points": [
        [12.34, 56.78], // x0, y0 (starting point of the polygon)
        [90.12, 34.56], // x1, y1
        [78.91, 23.45], // x2, y2
        [67.89, 98.76], // x3, y3
        [54.32, 10.01]  // x4, y4
      ]
    },
    {
      "track_id": 3,
      "id": 3, 
      "category_id": 3,
      "is_keyframe": true,
      "type": "polyline", // refers to the annotation type (polyline)
      "points": [
        [12.34, 56.78], // x0, y0 (starting point of the polyline)
        [90.12, 34.56], // x1, y1
        [78.91, 23.45], // x2, y2
        [67.89, 98.76], // x3, y3
        [54.32, 10.01]  // x4, y4
      ]
    },
    {
      "track_id": 4,
      "id": 4,
      "category_id": 4,
      "is_keyframe": true,
      "type": "point", // refers to the annotation type (keypoint)
      "points": [
        [12.34, 56.78] // x, y (coordinates of keypoint)
      ]
    },
  ],
}

3D point cloud

Segmentation label

The annotations array contains the different objects ("annotations") in the label with their category (the category_id should correspond to an id defined in the categories).

The point_annotations array contains the object/annotation id for each point in the point cloud. The order of the ids in this array is the same as the order of the points in the point cloud.

{
  "format_version": "0.1",
  "annotations": [
    {
      "track_id": 1, // the track id. A single object has the same track_id across frames.
      "id": 1, // this is a legacy field and is always equal to track_id.
      "category_id": 1 // the category id
    },
    {
      "track_id": 2,
      "id": 2,
      "category_id": 1
    },
    {
      "track_id": 3,
      "id": 3,
      "category_id": 4
    }
  ],
  "point_annotations": [0, 0, 0, 3, 2, 2, 2, 1, 3...], // refers to track ids
}

Cuboid label

{
  "format_version": "0.2",
  "annotations": [ // list of cuboid annotations, see below
    {
      "track_id": 1, // the track id. A single object has the same track_id across frames.
      "id": 1, // this is a legacy field and is always equal to track_id
      "type": "cuboid",
      ...
    },
    { 
      ... 
    }
  ],
  "links": [
    {
      "from_id": 1,
      "to_id": 2,
      "attributes": {} // the link attributes
    }
  ]
}

Name	Type	Description
format_version	string	Format version.
annotations	array of cuboid annotations	List of the cuboid annotations.
links	array of link annotations	List of the links

Cuboid annotation

A cuboid annotation represents a single cuboid in a point cloud (frame).

{
  "track_id": 1, // the track id. A single object has the same track_id across frames.
  "id": 1, // this is a legacy field and is always equal to track_id
  "category_id": 1,
  "type": "cuboid",
  "position": {
    "x": 0.0,
    "y": 0.2,
    "z": 0.5
  },
  "dimensions": {
    "x": 1.2,
    "y": 1,
    "z": 1
  },
  "yaw": 0.63,
  "rotation": {
    "qx": 0,
    "qy": 0.0491566,
    "qz": 0.3096865,
    "qw": 0.9495672
  },  // only when 3D cuboid rotation is enabled in dataset settings
  "is_keyframe": true,  // only in sequences
  "index": 0,  // only in sequences 
}

Name	Type	Description
id	integer	Object id.
category_id	integer	Category id.
type	string	Object type, which is always "cuboid" for cuboid annotations.
position	object: { "x": float, "y": float, "z": float }	XYZ position of the center of the cuboid in world coordinates.
dimensions	object: { "x": float, "y": float, "z": float }	Dimensions of the cuboid. "x" corresponds to the length, "y" to the width, and "z" to the height. See diagram 1.
yaw	float	Cuboid rotation along the z-axis in radians between [-π, π]. 0 yaw corresponds to a cuboid aligned with the x-axis pointing to increasing x-values. The yaw value increases with a counter-clockwise rotation up to π, and decreases with a clockwise rotation up to -π. See diagram 2.
rotation	object: { "qx": float, "qy": float, "qz": float, "qw": float }	Cuboid rotation defined as a rotation quaternion. Only available when 3D rotation is enabled in the dataset settings (under "Labeling").
track_id	integer	Track ID of the object. This ID is used to track an object over multiple frames. Only relevant for sequences.
is_keyframe	boolean	Whether this cuboid annotation is a keyframe or an interpolated frame. Only relevant for sequences.
index	integer	The frame index. Only relevant for sequences.

Diagram 1: x and y attributes of the cuboid dimensions. The red arrow shows the cuboid heading.

Diagram 2: yaw rotation of a cuboid. The red arrow shows the cuboid heading. yaw = π/2 corresponds to a heading in the direction of increasing y values, while yaw = -π/2 corresponds to a heading in the direction of decreasing y values.

Vector label (polygon, polyline, keypoint)

  "format_version": "0.1",
  "annotations": [
    {
      "track_id": 1, // the track id. A single object has the same track_id across frames.
      "id": 1, // this is a legacy field and is always equal to track_id
      "category_id": 2,
      "type": "polygon", // refers to the annotation type (polygon)
      "points": [
        [12.34, 56.78, 0], // x0, y0, z0 (starting point of the polygon)
        [90.12, 34.56, 0], // x1, y1, z1
        [78.91, 23.45, 0], // x2, y2, z2
        [67.89, 98.76, 0], // x3, y3, z3
        [54.32, 10.01, 0]  // x4, y4, z4
      ],
      "is_keyframe": true, // only in sequences
      "index": 0 // only in sequences 
    },
    {
      "track_id": 2,
      "id": 2,
      "category_id": 3,
      "type": "polyline", // refers to the annotation type (polyline)
      "points": [
        [12.34, 56.78, 0], // x0, y0, z0 (starting point of the polyline)
        [90.12, 34.56, 0], // x1, y1, z1
        [78.91, 23.45, 0], // x2, y2, z2
        [67.89, 98.76, 0], // x3, y3, z3
        [54.32, 10.01, 0]  // x4, y4, z4
      ],
      "is_keyframe": false, // only in sequences
      "index": 1 // only in sequences 
    },
    {
      "track_id": 3,
      "id": 3,
      "category_id": 4,
      "type": "point", // refers to the annotation type (keypoint)
      "points": [
        [12.34, 56.78, 0] // x, y, z (coordinates of keypoint)
      ],
      "is_keyframe": false, // only in sequences
      "index": 2 // only in sequences 
    }
  ]
}

3D point cloud sequence

Segmentation label

{
  "format_version": "0.2",
  "frames": [
    { ... },
    { ... },
    { ... }
  ]
}

Where each frames object has the following format:

{
  "format_version": "0.2",
  "annotations": [
    {
      "track_id": 1, // the track id. A single object has the same track_id across frames.
      "id": 1, // this is a legacy field and is always equal to track_id
      "category_id": 1, // the category id
    },
    {
      "track_id": 2,
      "id": 2,
      "category_id": 1,
    },
    {
      "track_id": 3,
      "id": 3,
      "category_id": 4,
    },
  ],
  "point_annotations": [0, 0, 0, 3, 2, 2, 2, 1, 3...], // refers to object ids
}

Cuboid label

{
  "format_version": "0.2",
  "frames": [
    { ... },
    { ... },
    { ... }
  ]
}

Name	Type	Description
format_version	string	Format version.
frames	array of cuboid labels	List of cuboid labels (one per frame in the sequence).

Vector label (polygon, polyline, keypoint)

Format of the attributes field in client.get_label():

{
  "format_version": "0.2",
  "frames": [
    { ... },
    { ... },
    { ... }
  ],
  "links": [
    {
      "from_id": 1,
      "to_id": 2,
      "attributes": {} // the link attributes
    }
  ]
}

Name	Type
format_version	string	Format version.
frames	array of vector labels	List of vector labels (one per frame in the sequence).
links	array of link annotations	List of the links

Multi-sensor sequence

When uploading pre-labels for multi-sensor samples, make sure that the order of the sensors is the same in the label as in the sample. It is not sufficient for the sensors to have the same name, the order must also match.

{
  "sensors": [
    {
      "name": "Lidar", 
      "task_type": "pointcloud-cuboid-sequence",
      "attributes": { ... }
    },
    {
      "name": "Camera 1", 
      "task_type": "image-vector-sequence",
      "attributes": { ... } 
    },
    ...
  ],
  "links": [
    {
      "from_id": 1,
      "to_id": 2,
      "attributes": {} // the link attributes
    }
  ]
}

Name	Type	Description
sensors	array of sensors	List of the sensors with label attributes.
links	array of link annotations	List of the links

Sensor

Name	Type	Description
name	string	Name of the sensor.
task_type	string	The task type of the sensor. Currently, pointcloud-cuboid-sequence and image-vector-sequence are supported.
attributes	object	The label attributes for the sensor. Currently, 3D point cloud sequence and image sequence are supported.

Object attributes

Objects in the annotations list can optionally also contain an attributes field to store object-level attributes. Make sure to properly configure the label editor if you're using object-level attributes.

{
  "format_version": "0.1",
  "annotations": [
    {
      "id": 1, 
      "category_id": 1,
      "attributes": { // object-level attributes
        "is_crowd": "1",
        "color": "red"
      }
    },
    {
      "id": 2, 
      "category_id": 1,
      "attributes": {
        "is_crowd": "0",
        "color": "blue"
      }
    },
    {
      "id": 3, 
      "category_id": 4,
      "attributes": {
        "is_crowd": "1",
        "color": "yellow"
      }
    }
  ],
  ...
}

Image attributes

You can also define image-level attributes. These can be useful in image classification tasks. Make sure to properly configure the label editor if you're using image-level attributes.

{
  "format_version": "0.1",
  "annotations": [...],
  "image_attributes": { // sample-level attributes
    "scene_type": "crossroads",
    "weather": "sunny"
  }
}

Links

The links are stored at the top level of the annotations.

[
  {
    "from_id": 1,
    "to_id": 2,
    "attributes": {
      "side": "left",
      "strength": 10
    }
]

Name	Type	Description
from_id	number	Link's object/track origin
to_id	number	Link's object/track destination
attributes	object	The link attributes.