Peak Signal-to-Noise Ratio (PSNR) is a measure of the quality of reconstruction of a signal. It is commonly used to evaluate the performance of image and video compression algorithms, as well as to evaluate the quality of denoising algorithms. The PSNR is defined as the ratio between the maximum possible power of a signal and the power of the difference between the original and the reconstructed signals. It is expressed in decibels (dB).
The PSNR is calculated as follows:
PSNR = 10 * log10(MAX^2 / MSE)
where MAX is the maximum possible pixel value of the image (e.g., 255 for 8-bit grayscale images), and MSE is the mean squared error between the original and reconstructed images. The higher the PSNR value, the better the quality of the reconstructed image.
It is important to note that PSNR is not always an accurate indicator of the perceptual quality of an image or video. This is because it does not take into account the human visual system, which is more sensitive to some types of errors than others.