Easiest way to annotate data with bounding boxes – 2023

Hey guys in today’s blog we will see how to annotate data with bounding boxes in the easiest way possible.

In the age of artificial intelligence and machine learning, high-quality annotated data is paramount. One common method of data annotation is the use of bounding boxes.

Bounding boxes are rectangular or square frames that enclose specific objects or regions of interest within an image. They are fundamental in computer vision, object detection, and image classification tasks.

Understanding Bounding Boxes

Before we dive into the annotation process, let’s ensure we have a clear understanding of what bounding boxes are and why they are essential.

What Are Bounding Boxes?

Bounding boxes are geometric shapes that define the location and dimensions of objects within an image. They are typically represented by four coordinates: (x_min, y_min, x_max, y_max), which denote the minimum and maximum values for the x and y coordinates, respectively.

Why Are Bounding Boxes Important?

Bounding boxes serve multiple purposes:

  1. Object Localization: Bounding boxes precisely locate objects within an image, enabling object detection algorithms to identify and classify them accurately.
  2. Data Augmentation: Annotated data with bounding boxes can be used to create augmented datasets, enhancing the robustness of machine learning models.
  3. Training Supervised Models: Bounding box annotations are crucial for training supervised models in tasks such as image segmentation and object recognition.

How to annotate data with bounding boxes?

Step 1 – Install LabelImg

  • Open the terminal in your system and run the following command.
  • pip install labelImg
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  • We can see the labelImg library is installed successfully.

Step 2 – Open the images folder

  • Open the images folder where all the images are located.
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Step 3 – Let’s annotate images

  • Open the terminal in the folder above and type labelImg.
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  • Hit Enter and a GUI will open.
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  • Now we need to change 3 things:
    • Open Dir – Select the folder in which your images are stored.
    • Change Save Dir – Folder where you need to store the annotations. I have created an empty folder named labels.
    • Save Format – lableImg has 3 save formats YOLO, CreateML, and PascalVOC. I have selected YOLO for my usecase.
  • After you select all these things, the first image in your folder will open up.
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  • I will mark all the number plates in this image.
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  • After drawing all the bounding boxes, click on Save and click on Next Image.
  • As soon as you do this step, the annotations for this image will get stored in the labels folder.
  • Each line shows 5 elements – [class, x_min, y_min, x_max, y_max].
  • In this Image we had 4 number plates, hence we have 4 lines in the annotation file.
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  • Do this step for all the images.
  • Once all the annotations are done, you will see the labels folder like this.
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Annotating data with bounding boxes is a crucial step in training accurate machine learning models. With the right tools and a systematic approach, you can simplify the annotation process and ensure the quality of your annotated dataset.

Now that you’re equipped with the knowledge of the easiest way to annotate data with bounding boxes, you can kickstart your computer vision projects with confidence.

So in this way you can annotate data with bounding boxes. This was all for this blog guys, hope you enjoyed this blog…


What is the significance of bounding boxes in computer vision?

Bounding boxes are essential in computer vision as they precisely define the location and dimensions of objects within an image, enabling accurate object detection and classification.

Can I use free annotation tools for large-scale projects?

Yes, there are free annotation tools like LabelImg that are suitable for both small and large-scale annotation projects. However, premium tools may offer advanced features for efficiency.

Are there any open-source alternatives to RectLabel for Mac users?

Yes, there are open-source alternatives like LabelImg that work on macOS and other operating systems. These tools provide similar annotation capabilities.

How can annotated data with bounding boxes improve model accuracy?

Annotated data with bounding boxes can improve model accuracy by providing precise object localization, enabling better training of object detection algorithms.

Can I automate the annotation process using AI?

Yes, there are AI-powered annotation tools available that can automate parts of the annotation process. These tools can be especially useful for speeding up large-scale projects.

Read my last article – Check Data Drift in DataBricks using Evidently and MLflow

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Abhishek Sharma
Abhishek Sharma

Started my Data Science journey in my 2nd year of college and since then continuously into it because of the magical powers of ML and continuously doing projects in almost every domain of AI like ML, DL, CV, NLP.

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