How to Get Image Size in Python Using OpenCV

When working with images in Python, especially in applications related to computer vision, it's often necessary to obtain the dimensions of an image. This is a fundamental step for tasks like image processing, analysis, and transformations. One of the most popular libraries for these purposes is OpenCV. In this post, we will explore how to get the size of an image using OpenCV in Python.

Why Knowing Image Size is Important

Before diving into the code, let's understand why knowing the size of an image is crucial. Image dimensions, which include the width and height of the image, are essential for:

• Resizing or scaling images to a specific size.
• Cropping regions from an image.
• Navigating through the image matrix for pixel manipulation.
• Preparing images for machine learning models that require inputs of a certain size.

Getting Started with OpenCV

To get started, ensure you have OpenCV installed in your Python environment. If not, you can easily install it using pip:

pip install opencv-python

Reading an Image

First, we need to load an image. OpenCV provides the cv2.imread() function for this purpose. Here's how to use it:

import cv2

# Load an image using OpenCV
image = cv2.imread('path_to_your_image.jpg')

Make sure to replace 'path_to_your_image.jpg' with the actual path to your image.

Getting the Image Size

Once the image is loaded, you can get its size (dimensions) using the shape attribute. The shape attribute returns a tuple representing the dimensions of the array, which for images, corresponds to the height, width, and the number of channels (for color images).

Here's how you can get the width and height of an image:

height, width = image.shape[:2]
print(f"Width: {width}, Height: {height}")

This code snippet will print the width and height of the image. Note that we used image.shape[:2] to get only the first two elements of the shape tuple, which are the height and width, respectively. The number of channels is omitted since it's not needed for just getting the size.

Conclusion

Obtaining the size of an image is a straightforward task when using OpenCV in Python. By simply reading the image and accessing its shape attribute, you can quickly get the dimensions of the image. This information is invaluable for various image manipulation and processing tasks, making it a fundamental skill for developers and researchers working in the field of computer vision.

Remember, mastering the basics like these will make your journey into more complex image processing tasks much smoother. Happy coding!