Image Pyramid using OpenCV | Python

Image Pyramids are one of the most beautiful concept of image processing.Normally, we work with images with default resolution but many times we need to change the resolution (lower it) or resize the original image in that case image pyramids comes handy.

The pyrUp() function increases the size to double of its original size and pyrDown() function decreases the size to half. If we keep the original image as a base image and go on applying pyrDown function on it and keep the images in a vertical stack, it will look like a pyramid. The same is true for upscaling the original image by pyrUp function.

Once we scale down and if we rescale it to the original size, we lose some information and the resolution of the new image is much lower than the original one.

Below is an example of Image Pyramiding –

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import cv2
import matplotlib.pyplot as plt
  
img = cv2.imread("images/input.jpg")
  
layer = img.copy()
  
for i in range(4):
    plt.subplot(2, 2, i + 1)
  
    # using pyrDown() function
    layer = cv2.pyrDown(layer)
  
    plt.imshow(layer)
    cv2.imshow("str(i)", layer)
    cv2.waitKey(0)
      
  
cv2.destroyAllWindows()

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Output:

Advantages of Image pyramids:

  • Lowering of resolution
  • Getting various sizes of image
  • Image Blending
  • Edge detection


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