Label Studio

Annotating data using Label Studio.

Label Studio is one of the leading open-source annotation platforms available to data scientists and ML practitioners. It is used to create or edit datasets that you can then use as part of training or validation workflows. It supports a broad range of annotation types, including:

  • Computer Vision (image classification, object detection, semantic segmentation)

  • Audio & Speech (classification, speaker diarization, emotion recognition, audio transcription)

  • Text / NLP (classification, NER, question answering, sentiment analysis)

  • Time Series (classification, segmentation, event recognition)

  • Multi-Modal / Domain (dialogue processing, OCR, time series with reference)

When would you want to use it?

If you need to label data as part of your ML workflow, that is the point at which you could consider adding the optional annotator stack component as part of your ZenML stack.

We currently support the use of annotation at the various stages described in the main annotators docs page, and also offer custom utility functions to generate Label Studio label config files for image classification and object detection. (More will follow in due course.)

The Label Studio integration currently is built to support workflows using the following three cloud artifact stores: AWS S3, GCP/GCS, and Azure Blob Storage. Purely local stacks will currently not work if you want to do add the annotation stack component as part of your stack.

How to deploy it?

The Label Studio Annotator flavor is provided by the Label Studio ZenML integration, you need to install it, to be able to register it as an Annotator and add it to your stack:

zenml integration install label_studio

You will then need to obtain your Label Studio API key. This will give you access to the web annotation interface. (The following steps apply to a local instance of Label Studio, but feel free to obtain your API key directly from your deployed instance if that's what you are using.)

git clone
cd label-studio
docker-compose up -d # starts label studio at http://localhost:8080

Then visit http://localhost:8080/ to log in, and then visit http://localhost:8080/user/account and get your Label Studio API key (from the upper right-hand corner). You will need it for the next step. Keep the Label Studio server running, because the ZenML Label Studio annotator will use it as the backend.

At this point you should register the API key under a custom secret name, making sure to replace the two parts in <> with whatever you choose:

zenml secret create label_studio_secrets --api_key="<your_label_studio_api_key>"

Then register your annotator with ZenML:

zenml annotator register label_studio --flavor label_studio --api_key="{{label_studio_secrets.api_key}}"

# for deployed instances of Label Studio, you can also pass in the URL as follows, for example:
# zenml annotator register label_studio --flavor label_studio --authentication_secret="<LABEL_STUDIO_SECRET_NAME>" --instance_url="<your_label_studio_url>" --port=80

When using a deployed instance of Label Studio, the instance URL must be specified without any trailing / at the end. You should specify the port, for example, port 80 for a standard HTTP connection. For a Hugging Face deployment (the easiest way to get going with Label Studio), please read the Hugging Face deployment documentation.

Finally, add all these components to a stack and set it as your active stack. For example:

zenml stack copy default annotation
zenml stack update annotation -a <YOUR_CLOUD_ARTIFACT_STORE>
# this must be done separately so that the other required stack components are first registered
zenml stack update annotation -an <YOUR_LABEL_STUDIO_ANNOTATOR>
zenml stack set annotation
# optionally also
zenml stack describe

Now if you run a simple CLI command like zenml annotator dataset list this should work without any errors. You're ready to use your annotator in your ML workflow!

How do you use it?

ZenML assumes that users have registered a cloud artifact store and an annotator as described above. ZenML currently only supports this setup, but we will add in the fully local stack option in the future.

ZenML supports access to your data and annotations via the zenml annotator ... CLI command.

You can access information about the datasets you're using with the zenml annotator dataset list. To work on annotation for a particular dataset, you can run zenml annotator dataset annotate <dataset_name>.

Our computer vision end to end example is the best place to see how all the pieces of making this integration work fit together. What follows is an overview of some key components to the Label Studio integration and how it can be used.

Label Studio Annotator Stack Component

Our Label Studio annotator component inherits from the BaseAnnotator class. There are some methods that are core methods that must be defined, like being able to register or get a dataset. Most annotators handle things like the storage of state and have their own custom features, so there are quite a few extra methods specific to Label Studio.

The core Label Studio functionality that's currently enabled includes a way to register your datasets, export any annotations for use in separate steps as well as start the annotator daemon process. (Label Studio requires a server to be running in order to use the web interface, and ZenML handles the provisioning of this server locally using the details you passed in when registering the component unless you've specified that you want to use a deployed instance.)

Standard Steps

ZenML offers some standard steps (and their associated config objects) which will get you up and running with the Label Studio integration quickly. These include:

  • LabelStudioDatasetRegistrationConfig - a step config object to be used when registering a dataset with Label studio using the get_or_create_dataset step

  • LabelStudioDatasetSyncConfig - a step config object to be used when registering a dataset with Label studio using the sync_new_data_to_label_studio step. Note that this requires a ZenML secret to have been pre-registered with your artifact store as being the one that holds authentication secrets specific to your particular cloud provider. (Label Studio provides some documentation on what permissions these secrets require here.)

  • get_or_create_dataset step - This takes a LabelStudioDatasetRegistrationConfig config object which includes the name of the dataset. If it exists, this step will return the name, but if it doesn't exist then ZenML will register the dataset along with the appropriate label config with Label Studio.

  • get_labeled_data step - This step will get all labeled data available for a particular dataset. Note that these are output in a Label Studio annotation format, which will subsequently be converted into a format appropriate for your specific use case.

  • sync_new_data_to_label_studio step - This step is for ensuring that ZenML is handling the annotations and that the files being used are stored and synced with the ZenML cloud artifact store. This is an important step as part of a continuous annotation workflow since you want all the subsequent steps of your workflow to remain in sync with whatever new annotations are being made or have been created.

Helper Functions

Label Studio requires the use of what it calls 'label config' when you are creating/registering your dataset. These are strings containing HTML-like syntax that allow you to define a custom interface for your annotation. ZenML provides three helper functions that will construct these label config strings in the case of object detection, image classification, and OCR. See the integrations.label_studio.label_config_generators module for those three functions.

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