How to Select Image Annotation Tools & Techniques

How to Select Image Annotation Tools & Techniques

Selecting the proper image annotation technique is critical to machine learning (ML) performance because the accuracy and efficiency of computer vision applications depend heavily on the quality and consistency of the annotations.

Choosing the wrong technique can result in inaccurate or incomplete annotations. This leads to poor performance in object detection, object recognition, object classification, object localization, and image search.

Different annotation techniques have different levels of complexity and resource requirements, so selecting the right technique is important to ensure efficient use of time, money, and other resources.

Types of Image Annotation Techniques

  1. Bounding Box Annotation
  2. Semantic Segmentation Annotation
  3. Polygon Annotation
  4. Cuboids
  5. Key points
  6. Lines and Arrows

Bounding Box Annotation

This type of annotation is used for object detection tasks, where an object in an image needs to be located and identified. Bounding box annotation involves drawing a rectangle around the object, indicating its location in the image.

It is commonly used in applications such as autonomous driving, where vehicles need to identify and avoid obstacles on the road. It is also used in ecommerce and retail to identify products in images. This information is used to improve image search capabilities, enabling customers to find products more easily.

Semantic Segmentation Annotation

This involves dividing an image into different regions, each of which corresponds to a different object or background. Each region is then labeled with a semantic tag, such as “car,” “tree,” or “road”.

Semantic segmentation annotation is used in medical imaging to identify different types of tissues or organs in an image. This information is used to assist in diagnosis and treatment planning. It is also used in precision agriculture to identify and map crop types and other vegetation in satellite or drone imagery. This information is then used to identify areas of stress or disease, or to predict yield.

Polygon Annotation

This involves drawing a series of interconnected lines to outline an object in an image. This type of annotation is often used for objects that do not have a clear rectangular shape, such as shirts or handbags.

Polygon annotation is commonly used in retail and ecommerce applications to improve the accuracy and efficiency of visual search, product recognition, and object detection. Polygon annotations can be used to create precise 3D models of objects or environments, which can then be used in AR experiences.

For example, 3D furniture models can be used to place virtual furniture in the user’s environment in a realistic and accurate way, allowing them to see how it would look in their home before making a purchase.


These are a type of image annotation used to identify objects in 3D space. This type of annotation involves drawing a 3D box around an object in an image to indicate its position and orientation in space. Cuboid annotation can be used in robotics to help robots identify and manipulate objects in three-dimensional space. For example, in a warehouse setting, cuboid annotation can be used to identify the location and orientation of items on shelves, allowing robots to pick and pack items more efficiently.

Cuboids are also heavily used in autonomous vehicle applications to identify and track other vehicles, pedestrians, and objects in the environment, enabling the vehicle to navigate safely and avoid collisions.

Key points

This is a type of image annotation used to identify specific areas or features in an image. This type of annotation involves marking the key points or points of interest within an image, such as the corners of a building or the location of a particular object. It can be used to help robots identify and manipulate objects to perform complex assembly tasks with greater accuracy and efficiency.

It is also used in sports analysis to identify and track the movement of athletes. In soccer, key points annotation can be used to track the position and movement of players and the ball during a game, providing valuable data for coaches and analysts.

Lines and Arrows

This is a type of image annotation used to highlight specific areas or features in an image. This type of annotation involves drawing lines or arrows on the image to indicate the direction of movement or to emphasize certain aspects of the image. In medical imaging, lines and arrows annotation can be used to highlight specific features or anomalies within an image, such as a tumor or an area of inflammation. This information can be used by radiologists to make more accurate diagnoses and develop treatment plans.


Lines and arrows annotation is also used in construction and engineering to mark up blueprints and schematics, highlighting specific features or indicating areas of concern, to improve communication and collaboration among team members and complete projects on time and on budget.

Benefits of Image Annotation Tools

Image annotation tools are software applications that enable users to annotate digital images for use in machine learning (ML) and computer vision applications. These tools typically provide a user-friendly interface for creating annotations of various types, such as bounding boxes, polygons, lines, and more. Some annotation tools also include built-in quality control and assurance features to ensure the accuracy and consistency.

Many annotation tools offer integration with ML frameworks and platforms, making it easy to export annotations and incorporate them into models. There are numerous image annotation tools available, both open source and commercial, each with its own features, strengths, and limitations. Choosing the right tool depends on various factors, such as the type of annotations needed, the size of the dataset and the available resources, amongst others.

Benefits of Image Annotation Partners

Working with an image annotation partner can be highly beneficial for defining and implementing an effective annotation strategy. An image annotation partner can provide expertise and guidance on selecting the appropriate annotation techniques and tools for specific use cases and datasets, taking into consideration factors such as accuracy, consistency, and scalability. They can also help define annotation workflows and quality control processes to ensure the highest possible quality of annotations.

An image annotation partner can assist with managing annotation projects, including recruiting and training annotators, managing timelines and budgets, and ensuring data security and privacy. By partnering with a data annotation provider, organizations can benefit from the expertise and resources needed to create accurate and reliable annotations, ultimately leading to improved ML and computer vision performance.

Learn more about how Sama can annotate data for computer vision use cases with high accuracy while meeting the challenges of scale.

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