OpenCV is a powerful library in Python used for computer vision tasks. One of its functionalities is to save images to your disk using the cv2.imwrite function. This article will guide you through using cv2.imwrite on a Windows environment, providing practical examples and explaining how to execute these tasks via the Command Prompt (CMD).

Understanding cv2.imwrite

The cv2.imwrite function is used to write an image to a specified file. It takes two primary arguments: the file path where the image will be saved and the image data itself. This function is part of the OpenCV library, which is widely used for image processing tasks.

Prerequisites

Before you can use cv2.imwrite, ensure you have Python and OpenCV installed on your Windows machine. You can install OpenCV via pip:

pip install opencv-python

Examples

1. Basic Example of cv2.imwrite

   Let's start with a simple example where we read an image and save it to a different file.

   import cv2
   
   # Read an image from a file
   image = cv2.imread('input.jpg')
   
   # Save the image to a new file
   cv2.imwrite('output.jpg', image)

   To execute this script, save it as save_image.py and run it using the Command Prompt:

   python save_image.py

2. Convert and Save Image in Different Format

   You can also convert an image to a different format before saving it. For example, converting a JPEG image to PNG:

   import cv2
   
   # Read an image from a file
   image = cv2.imread('input.jpg')
   
   # Save the image in PNG format
   cv2.imwrite('output.png', image)

   Execute this script similarly by saving it as convert_and_save.py and running:

   python convert_and_save.py

3. Saving Images with Compression

   OpenCV allows you to specify the compression level when saving images. For JPEG images, you can set the quality from 0 to 100 (higher is better quality). For PNG images, you can set the compression level from 0 to 9 (lower is better quality).

   import cv2
   
   # Read an image from a file
   image = cv2.imread('input.jpg')
   
   # Save the image with JPEG quality of 90
   cv2.imwrite('output_quality.jpg', image, [cv2.IMWRITE_JPEG_QUALITY, 90])
   
   # Save the image with PNG compression level of 3
   cv2.imwrite('output_compression.png', image, [cv2.IMWRITE_PNG_COMPRESSION, 3])

   Run this script using:

   python save_with_compression.py

Conclusion

The cv2.imwrite function is a straightforward yet powerful tool for saving images in various formats and with different compression settings. By following the examples above, you can effectively manage image files on your Windows system using Python and OpenCV.