Rotating an Image in OpenCV

Rotating an image is a common operation in image processing, and OpenCV provides simple methods to achieve this. This guide will walk you through the basic steps to rotate an image using OpenCV.

Installation

First, ensure you have OpenCV installed. You can install it using pip:

pip install opencv-python 

Loading an Image

To rotate an image, you first need to load it. Use the cv2.imread function to read the image from a file.

import cv2 
# Load the image 
image = cv2.imread('path_to_your_image.jpg') 

Rotating the Image

OpenCV allows you to rotate an image by creating a rotation matrix and applying it using cv2.warpAffine.

Get the Image Dimensions:

(height, width) = image.shape[:2] 

Set the Rotation Angle and Center:

1. Choose the angle for rotation and the center point around which to rotate.

angle = 45 # Rotation angle in degrees 
center = (width // 2, height // 2) # Center of the image 

Create the Rotation Matrix:

1. Use cv2.getRotationMatrix2D to create the rotation matrix.

rotation_matrix = cv2.getRotationMatrix2D(center, angle, 1.0) 

Apply the Rotation:

1. Use cv2.warpAffine to apply the rotation to the image.

rotated_image = cv2.warpAffine(image, rotation_matrix, (width, height)) 

Displaying the Images

You can display the original and rotated images using cv2.imshow. This helps you see the result.

# Display the original image 
cv2.imshow('Original Image', image) 
# Display the rotated image 
cv2.imshow('Rotated Image', rotated_image) 
# Wait for a key press and close the windows 
cv2.waitKey(0) 
cv2.destroyAllWindows() 

Complete Code Example

Here’s the complete code to rotate an image using OpenCV:

import cv2 
# Load the image 
image = cv2.imread('path_to_your_image.jpg') 
# Get the image dimensions 
(height, width) = image.shape[:2] 
# Set the rotation angle and center 
angle = 45 # Rotation angle in degrees 
center = (width // 2, height // 2) # Center of the image 
# Create the rotation matrix 
rotation_matrix = cv2.getRotationMatrix2D(center, angle, 1.0) 
# Apply the rotation 
rotated_image = cv2.warpAffine(image, rotation_matrix, (width, height)) 
# Display the original image 
cv2.imshow('Original Image', image) 
# Display the rotated image 
cv2.imshow('Rotated Image', rotated_image) 
# Wait for a key press and close the windows 
cv2.waitKey(0) 
cv2.destroyAllWindows()