Python/compression/peak_signal_to_noise_ratio.py

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"""
Peak signal-to-noise ratio - PSNR
https://en.wikipedia.org/wiki/Peak_signal-to-noise_ratio
Source:
https://tutorials.techonical.com/how-to-calculate-psnr-value-of-two-images-using-python
"""
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import math
import os
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import cv2
import numpy as np
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def psnr(original: float, contrast: float) -> float:
mse = np.mean((original - contrast) ** 2)
if mse == 0:
return 100
PIXEL_MAX = 255.0 # noqa: N806
PSNR = 20 * math.log10(PIXEL_MAX / math.sqrt(mse)) # noqa: N806
return PSNR
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def main() -> None:
dir_path = os.path.dirname(os.path.realpath(__file__))
# Loading images (original image and compressed image)
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original = cv2.imread(os.path.join(dir_path, "image_data/original_image.png"))
contrast = cv2.imread(os.path.join(dir_path, "image_data/compressed_image.png"), 1)
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original2 = cv2.imread(os.path.join(dir_path, "image_data/PSNR-example-base.png"))
contrast2 = cv2.imread(
os.path.join(dir_path, "image_data/PSNR-example-comp-10.jpg"), 1
)
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# Value expected: 29.73dB
print("-- First Test --")
print(f"PSNR value is {psnr(original, contrast)} dB")
# # Value expected: 31.53dB (Wikipedia Example)
print("\n-- Second Test --")
print(f"PSNR value is {psnr(original2, contrast2)} dB")
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if __name__ == "__main__":
main()