Cropping an Image in OpenCV

Cropping an image is a straightforward task in image processing, and OpenCV makes it easy to accomplish. This guide will show you how to crop 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 crop 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') 

Cropping the Image

Cropping an image involves selecting a region of interest (ROI) and extracting it from the image. You do this by specifying the coordinates of the top-left and bottom-right corners of the desired region.

Define the Coordinates:

1. Set the coordinates for the region you want to crop. For example:

x_start, y_start = 50, 50 # Top-left corner 
x_end, y_end = 200, 200 # Bottom-right corner 

Crop the Image:

1. Use array slicing to crop the image.

cropped_image = image[y_start:y_end, x_start:x_end] 

Displaying the Images

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

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

Complete Code Example

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

import cv2 
# Load the image 
image = cv2.imread('path_to_your_image.jpg') 
# Define the coordinates for cropping 
x_start, y_start = 50, 50 # Top-left corner 
x_end, y_end = 200, 200 # Bottom-right corner 
# Crop the image 
cropped_image = image[y_start:y_end, x_start:x_end] 
# Display the original image 
cv2.imshow('Original Image', image) 
# Display the cropped image 
cv2.imshow('Cropped Image', cropped_image) 
# Wait for a key press and close the windows 
cv2.waitKey(0) 
cv2.destroyAllWindows()