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How-to

How to annotate an image for AI: our complete guide

Written by
Nanobaly
Published on
2024-04-29
Reading time
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min
πŸ“˜ CONTENTS
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In our digital age, photos and other images play a key role. They're everywhere! Whether to share precious moments, document important events or promote products and services, images have become indispensable.

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However, for an image or photo to be fully exploitable by artificial intelligence (AI) systems, it needs to be appropriately annotated. This is where image annotation comes in, a step in the development of innovative solutions based on computer vision. But, you may ask, how does it work?

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In practice, the use of an application for image annotation, with quality control features and a user-friendly interface, is essential for Data Science teams, AI researchers and engineers. In addition, the creation and management of files or datasets from annotated images are important aspects of this process.

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AI image annotation: what's it all about?

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Image annotation involves adding descriptive information (or metadata), such as labels, categories or coordinates, to a digital image. This process enables AI systems to πŸ”— understand the visual content and perform specific tasks, such as object recognition, defect detection or scene analysis. The data to be annotated is sometimes πŸ”— pre-labeled by artificial intelligence - the image annotation task then consists of reviewing and correcting any label prediction errors.

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In other words, image annotation transforms raw visual data into structured data that can be used by machine learning algorithms.

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Why is annotating images or photos important in AI?

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In a world where πŸ”— Computer Vision are multiplying, image annotation is of paramount importance. Here are a few reasons that illustrate its essential role in AI development cycles:

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Training machine learning models

Deep learning algorithms require annotated datasets to train themselves to recognize patterns in an image and perform specific tasks. Without accurate annotations, these models would be unable to achieve high levels of performance.

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In-depth understanding of images

By annotating images, data specialists such as Data Labelers provide contextual information that enables AI systems to better grasp the visual content of an image. This in-depth understanding is essential for applications such as autonomous driving, safety monitoring or medical analysis.

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Process automation

Many companies will annotate images to automate previously manual tasks, such as product sorting, quality control or inventory management. This automation increases operational efficiency and reduces costs.

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Accessibility for the disabled

Image annotation can be used to generate detailed text descriptions, providing improved access to visual content for the visually impaired or blind. It's often overlooked, but these artificial intelligence techniques make a major contribution to digital accessibility!

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Different types of image annotation

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Depending on project objectives and requirements, different image annotation techniques can be employed. Here is a list of some of the most common approaches:

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Image classification

The πŸ”— image classification consists in assigning a global label to an image or photo, describing its main content. This method is particularly useful when it's not necessary to precisely locate objects or regions of interest. For example, classifying an image as "landscape" or "pet".

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Object detection

Object detection involves identifying and locating objects in an image or photo by drawing bounding boxes around them. The use of shapes such as rectangles or complex geometric forms helps to draw attention to specific details in annotated images. This technique is essential for applications such as traffic sign recognition, traffic monitoring or defect detection on production lines, among many other use cases!

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Image segmentation

Image segmentation involves dividing an image into distinct regions, each associated with a specific label. The πŸ”— annotators can drag their mouse to generate rectangular boxes. By dragging their cursor, Data Labelers adjust and highlight important areas of the photo, improving segmentation accuracy.

They can also personalize and enhance a photo to improve segmentation accuracy. This approach enables a finer understanding of visual content by the AI model, precisely delineating the contours of objects or areas of interest. Image segmentation is often used in fields such as medical imaging, scene analysis or facial recognition.

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Object tracking

Object tracking involves following the movement and position of a specific object through a sequence of images or video. This technique is particularly useful for behavior analysis, traffic monitoring or activity recognition.

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Image annotation tools

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To facilitate the annotation process, numerous software tools have been developed. Here are some of the most popular tools:

  • πŸ”— LabelMe : An open-source tool for annotating an image with bounding boxes, polygons or lines.
  • πŸ”— CVAT : An image and video annotation platform with advanced features, such as object tracking and team collaboration.
  • LabelImg: A simple, user-friendly graphics tool for annotating images with bounding boxes.
  • SuperAnnotate: A complete image annotation solution, offering πŸ”— semantic segmentationobject detection and classification. You can use SuperAnnotate to annotate, edit and save images.
  • V7: A versatile image annotation tool, supporting different types of annotation, such as bounding boxes, polygons and waypoints. With V7, it's easy to upload an image and process it online, thanks to its powerful and versatile Cloud interface.

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πŸ’‘ πŸ”— Click here to find out more about the different annotation platforms on the market!

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These tools generally offer users an intuitive user interface for annotating images, as well as project management, collaboration and export capabilities for annotated data in various formats used by data scientists.

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Image annotation process

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The image annotation process involves several key steps to ensure high-quality results. Here's an overview of the main steps:

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Defining objectives

Before you start annotating, it's essential to clearly define your project objectives. What information is to be extracted from the images? What quality criteria need to be met? A precise understanding of the objectives will enable you to choose the most appropriate annotation technique and ensure the consistency of the annotations.

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Data collection

The quality of training data is crucial to the success of machine learning models. It is therefore important to collect a representative, high-quality image dataset, covering a variety of scenarios and conditions.

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Annotator training

The πŸ”— annotators or Data Labelers play a key role in the annotation process. They need to be trained in annotation techniques, the tools used and project-specific guidelines. Thorough training upstream of projects guarantees consistent and accurate annotations.

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Image annotation

Once the annotators have been trained, the annotation process can begin. The annotators use the appropriate tools to add the required comments and information to the images, following the established guidelines.

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Quality assurance

To guarantee the quality of annotated data, a quality assurance process must be put in place. This may involve manual verification of annotations by experts, the use of benchmarks or consensus between several annotators, and the correction of any errors detected.

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File export and data integration

Once the images have been annotated, the data must be exported in a file format compatible with machine learning systems. It is also possible to export annotated photos in different formats for seamless integration into model training pipelines .

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For example, you can customize an annotated image or photo by adjusting brightness and contrast to better highlight annotations before exporting. This step may involve data transformation, cleansing or normalization to ensure seamless integration into model training pipelines .

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Challenges and considerations

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Although image annotation is a necessary step in the software development of Computer Vision solutions, it also presents several challenges:

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Cost and time

Manual image annotation can be a time-consuming and costly task, particularly when large datasets are involved. Optimization strategies, such as partial automation or the use of experienced annotators, can help reduce these costs.

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Consistency and precision

Maintaining the consistency and accuracy of annotations is essential to guarantee optimal performance of machine learning models. It is also important to highlight something interesting in an image to ensure annotation accuracy. Clear guidelines, thorough training and rigorous quality assurance processes are needed to achieve this goal.

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Scalability

As Computer Vision projects become increasingly complex, the ability to annotate large database sets efficiently becomes ever more important. Scalable, high-performance annotation tools, optimized processes and adequate resources are required to meet this major challenge.

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Data confidentiality and security

When annotating sensitive images, such as medical data or personal information, it is essential to put in place appropriate security and confidentiality measures to protect the privacy of the individuals concerned.

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Future trends and prospects

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Image annotation is a constantly evolving field, benefiting from technological advances and innovative new approaches. Here are a few trends and future prospects to keep an eye on:

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AI-accelerated annotation

Machine learning and artificial intelligence techniques are increasingly being used to speed up and improve the annotation process. Pre-trained models can be used to generate initial annotations, features which are then refined and corrected by human annotators.

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Crowdsourcing annotation

The πŸ”— crowdsourcingor open outsourcing, is an approach that is gaining in popularity for annotating large datasets. By calling on a host of online contributors, it's possible to speed up the annotation process while reducing costs. Beware, however, of the ethical aspects of this approach: do you really know who is preparing your data, and under what conditions? It is sometimes assumed that crowdsourcing is more expensive than hiring a specialized service provider: this is of course not true! Don't hesitate to contact us πŸ”— get a quote and compare, to see for yourself.

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Continuous annotation

In some cases, image annotation is not a one-off process, but rather a continuous effort. Machine learning models are constantly fed with new annotated data, enabling continuous performance improvement.

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Multimodal annotation

More and more applications require the annotation of multimodal data, combining images, πŸ”— videostext and other modalities. The use of photos in multimodal annotations enables a richer understanding of content. Multimodal annotation tools are emerging to meet these needs, offering a richer and more complete understanding of content.

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Standardization and standards

As image annotation matures, efforts are being made to standardize processes and data formats. Emerging standards will facilitate interoperability and collaboration between different industry players. Among other standardization issues, we also need to think about security! New standards such as πŸ”— NIST AI-600-1 are emerging and will gradually impose ethical and secure practices on the πŸ”— Data Labeling.

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In conclusion

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In AI, image annotation is a fundamental element in the development of high-performance computer vision solutions. By providing machine learning systems with structured information, this enables in-depth understanding of visual content and opens the way to revolutionary applications in a variety of fields.

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Although the image annotation process presents challenges in terms of cost, time and accuracy, ongoing technological advances and innovative new approaches promise to facilitate and optimize this crucial task. As computer vision applications multiply, image annotation will remain an essential pillar for fully exploiting the potential of artificial intelligence in visual data processing.